subxt-metadata

This release updates frame-decode to 0.18.1, which fixes V5 signer payload construction and improves how authorization extensions (like VerifyMultiSignature) are handled.

Fixed

• V5 signer payloads now correctly include the transaction extension version and call data as an immutable base implication, matching FRAME's transaction extension pipeline semantics. (paritytech/frame-decode#104)
• Unknown Option<T> transaction extensions are now encoded as None (0u8) by default, allowing transaction encoding to succeed on chains with optional extensions. (from frame-decode 0.17.2)

Changed

• VerifySignature now uses is_authorization_extension to declare itself as an authorization boundary, replacing the previous out.clear() side effects in encode_value_for_signer_payload_to and encode_implicit_to. (#2268, #2269)
• Update frame-decode from 0.17.1 to 0.18.1. (#2268)

This release updates frame-decode to 0.18.1, which fixes V5 signer payload construction and improves how authorization extensions (like VerifyMultiSignature) are handled.

Fixed

• V5 signer payloads now correctly include the transaction extension version and call data as an immutable base implication, matching FRAME's transaction extension pipeline semantics. (paritytech/frame-decode#104)
• Unknown Option<T> transaction extensions are now encoded as None (0u8) by default, allowing transaction encoding to succeed on chains with optional extensions. (from frame-decode 0.17.2)

Changed

• VerifySignature now uses is_authorization_extension to declare itself as an authorization boundary, replacing the previous out.clear() side effects in encode_value_for_signer_payload_to and encode_implicit_to. (#2268, #2269)
• Update frame-decode from 0.17.1 to 0.18.1. (#2268)

This release fixes an issue whereby setting the genesis hash in the SubstrateConfigBuilder had no effect, and improves the reliability of tests against public archival RPC endpoints.

Changed

• Update Artifacts (auto-generated) (#2245)
• tests: Exponential backoff for archival RPC public endpoints (#2244)

Fixed

• Fix: SubstrateConfigBuilder::set_genesis_hash is a no-op (#2236)

This release bumps the light-client smoldot crate to the latest version and adds several fixes.

Changed

• Bump smoldot (#2217)
• Update rust version (#2218)

Fixed

• Fix clippy (#2226)
• VerifySignature => VerifyMultiSignature tx extension rename to fix (#2197)
• chore: fix some minor issues in the comments (#2211)

[0.50.0] - 2025-12-17

This release version is a deliberately large bump up from 0.44.0 to signify the extent of the changes in this release.

The headline changes are as follows:

• Subxt is no longer head-of-chain only, and can work with historic blocks, all the way back to genesis. Note: user-provided type information is required to do this for very old (> ~2year old, ie pre-V14 metadata) blocks.
• The MVP subxt-historic crate has been removed, its functionality having been merged into Subxt.
• The subxt-core crate has been removed for now to make way for the above. Subxt itself continues to support WASM use cases.
  • For truly no-std functionality, the frame-decode crate now contains much of the underlying logic used throughout Subxt to encode and decode things, and we would like to expand the functionality here.
  • We would like feedback from any users of the subxt-core crate on how they use it, and will use this feedback to drive future work in this area.
• No more monitoring for runtime updates is needed; Subxt now works across different runtime versions automatically.
• Errors are no longer one big Error enum; instead different Subxt APIs return different errors, to limit the number of possible errors in any one place. These all convert into subxt::Error so this can continue to be used as a catch-all.
• Storage APIs have been redone, fixing some issues and giving much more control over iteration, as well as key and value decoding.

There are also a couple of organizational changes which aren't visible:

• We now follow the name.rs + name/submodule.rs convention instead of the name/mod.rs + name/submodule.rs convention.
• CI and testing updates hopefully ensure better organization and coverage with a greater number of different feature flags being tested.

This changes have results in many breaking changes across APIs, which I will try my best to summarize below.

A good place to look for a more holistic understanding of what's changes are the examples, both:

• The smaller single-file examples
• The larger project-based examples

For the smaller examples, start with the basic transaction submission example and then have a look at the blocks example and the storage example to give the best broad overview of the changes. Pick and choose others next depending on what suits.

A breakdown of the significant changes follows, to aid migration efforts:

Configuration

Before

Configuration (PolkadotConfig and SubstrateConfig) was type-only and didn't exist at the value level, and so you'd provide it to the client like so:

use subxt::{OnlineClient, PolkadotConfig};

let api = OnlineClient::<PolkadotConfig>::new().await?;

After

Configuration now exists at the value level too. This is because it has been extended with support for historic types and working with historic metadatas and spec versions. The same code as above will continue to work, but it's now possible to instantiate and tweak the configuration and then use _with_config methods to provide it, like so:

use subxt::{OnlineClient, PolkadotConfig};

let config = PolkadotConfig::builder()
    .use_historic_types(false)
    .build();
let api = OnlineClient::<PolkadotConfig>::new_with_config(config).await?;

The rules for when to use PolkadotConfig and SubstrateConfig remain the same:

• Use PolkadotConfig for the Polkadot Relay Chain.
• Use SubstrateConfig by default with other chains.
• You may need to modify the configuration to work with some chains, as before.

See the docs for PolkadotConfig and SubstrateConfig for more. One example to be aware of is that if you want to work with historic blocks with SubstrateConfig, you'll need to instantiate it yourself and provide historic type information before passing it to OnlineClient or OfflineClient.

Configuration: ExtrinsicParams

Aside from the new historic types support, a notable change to the configuration has been the simplification of transaction extensions, previously called ExtrinsicParams in our Config. Now, the type is called TransactionExtensions and the supporting traits have been simplified and named more appropriately (just TransactionExtensions and TransactionExtension), moving to rely more on frame-decode for the core logic. For any users that implement their own transaction extensions, migrating to the new traits is straightforward and I would encourage you to look at how the built-in transaction extensions are implemented for guidance here.

See (see #2177) for more details around this change.

Working at specific blocks

Before

Previously, you'd be able to select (within a limited range) which block to work at with APIs like so:

let api = OnlineClient::<PolkadotConfig>::new().await?;

let constants = api.constants();

let storage = api.storage().at(block_hash).await?;
let storage = api.storage().at_latest().await?;

let events = api.events().at(block_hash).await?;
let events = api.events().at_latest().await?;

let runtime_apis = api.runtime_api().at(block_hash).await?;
let runtime_apis = api.runtime_api().at_latest().await?;

After

Now, the block is selected first, like so:

let api = OnlineClient::<PolkadotConfig>::new().await?;

let constants = api.at_block(block_hash_or_number).await?.constants();
let constants = api.at_current_block().await?.constants();

let storage = api.at_block(block_hash_or_number).await?.storage();
let storage = api.at_current_block().await?.storage();

let events = api.at_block(block_hash_or_number).await?.events();
let events = api.at_current_block().await?.events();

let runtime_apis = api.at_block(block_hash_or_number).await?.runtime_apis();
let runtime_apis = api.at_current_block().await?.runtime_apis();

Notes:

• at_latest has been renamed to at_current_block and, like before, it fetches the current finalized block at the time of calling.
• at_current_block now accepts a block hash or block number, and returns a client that works in the context of that block.
• Constants were not previously retrieved at a given block; Subxt only knew about a single Metadata and so it was unnecessary. Now, constants are retrieved at a specific block like everything else (different blocks may have different Metadatas).
• A small thing: runtime_api() was renamed to runtime_apis() to be consistent with other APIs names.
• .tx() is now callable at a specific block, and uses this block for any account nonce and mortality configuration.

Working with blocks

Before

A .blocks() method accessed block-specific APIs for fetching and subscribing to blocks.

let api = OnlineClient::<PolkadotConfig>::new().await?;

// fetching:
let block = api.blocks().at(block_hash).await?;
let block = api.blocks().at_latest().await?;

// subscribing:
let mut blocks = api.blocks().subscribe_finalized().await?;
while let Some(block) = blocks_sub.next().await {
    let block = block?;

    let extrinsics = block.extrinsics().await?;
    for ext in extrinsics.iter() {
        // See the blocks example for more.
    }
}

After

Now that APIs are largely block-specific up front, we don't need separate APIs for block fetching, and so we move streaming blocks up a level, removing the .blocks() APIs.

let api = OnlineClient::<PolkadotConfig>::new().await?;

// fetching:
let block = api.at_block(block_hash_or_number).await?;
let block = api.at_current_block().await?;

// subscribing:
let mut blocks = api.stream_blocks().await?;
while let Some(block) = blocks_sub.next().await {
    let block = block?;

    // now, we instantiate a client at a given block, which gives back the
    // same thing as api.at_block() and api.at_current_block() does:
    let at_block = block.at().await?;

    let extrinsics = at_block.extrinsics().fetch().await?;
    for ext in extrinsics.iter() {
        // See the blocks example for more.
    }
}

Notes:

• Working with finalized blocks is always the default now, and API names are shortened to make them the easiest/most obvious to use.
• Use .at() at a given block to hand back a full client which can do anything at that block.
• api.blocks().subscribe_finalized() => api.stream_blocks().
• api.blocks().subscribe_best() => api.stream_best_blocks().
• api.blocks().subscribe_all() => api.stream_all_blocks().

Transactions

Before

Transactions were implicitly created at the latest block, and the APIs were disconnected from any particular block:

let api = OnlineClient::<PolkadotConfig>::new().await?;

// Submit an extrinsic, waiting for success.
let events = api
    .tx()
    .sign_and_submit_then_watch_default(&balance_transfer_tx, &from)
    .await?
    .wait_for_finalized_success()
    .await?;

After

Transactions are anchored to a given block but we continue to provide a .tx() method on the client as a shorthand for "create transactions at the current block".

let api = OnlineClient::<PolkadotConfig>::new().await?;

// Work at a specific block:
let at_block = api.at_current_block().await?;

// Submit the balance transfer extrinsic anchored at this block:
let events = at_block
    .tx()
    .sign_and_submit_then_watch_default(&balance_transfer_tx, &from)
    .await?
    .wait_for_finalized_success()
    .await?;

// A shorthand for the above:
let events = api
    .tx()
    .await? // This is the minimal change from the old APIs.
    .sign_and_submit_then_watch_default(&balance_transfer_tx, &from)
    .await?
    .wait_for_finalized_success()
    .await?;

Notes:

• SignableTransaction::signer_payload, SignableTransaction::sign and SignableTransaction::sign_with_account_and_signature now may return an error (which previously would have led to harder to diagnose issues), and the SignableTransaction type now has a lifetime (see #2177).
• We now use transactions instead of tx everywhere to align better with other API names, but continue to provide tx as a shorthand.
• The word partial is changed to signable in transaction APIs. "partial" was always a confusing name, and "signable" makes it much clearer what is being created; something that can be signed.
  • tx().create_partial_offline(..) => tx().create_signable_offline(..)
  • tx().create_v4_partial_offline(..) => tx().create_v4_signable_offline(..)
  • tx().create_v5_partial_offline(..) => tx().create_v5_signable_offline(..)
  • tx().create_partial(..) => tx().create_signable(..)
  • tx().create_v4_partial(..) => tx().create_v4_signable(..)
  • tx().create_v5_partial(..) => tx().create_v5_signable(..)
• tx().from_bytes(bytes) is added as an easy way to hand a pre-constructed transaction to Subxt to be submitted, removing the need for an ugly SubmittableTransaction::from_bytes method.

Storage Entries

Before

The codegen dealt with the heavy lifting of iterating storage maps at various depths (albeit with a bug), and on fetching an entry you had little control over how you handled the resulting bytes.

let api = OnlineClient::<PolkadotConfig>::new().await?;

//// Fetching:
let result = api
    .storage()
    .at_latest()
    .await?
    .fetch(&storage_query)
    .await?;

//// Iterating
let mut results = api
    .storage()
    .at_latest()
    .await?
    .iter(storage_query)
    .await?;
while let Some(Ok(kv)) = results.next().await {
    println!("Keys decoded: {:?}", kv.keys); // <- Broken in some cases
    println!("Key: 0x{}", hex::encode(&kv.key_bytes));
    println!("Value: {:?}", kv.value);
}

After

A redesign of the Storage APIs makes everything more unified, and allows working at specific storage entries in a much more flexible way than before, while moving logic out of the codegen, simplifying it, and into Subxt proper.

let api = OnlineClient::<PolkadotConfig>::new().await?;
let at_block = api.at_current_block().await?;

let account_balances = at_block
    .storage()
    .entry(storage_query)?;

//// Fetching:

// We can fetch multiple values from an entry:
let value1 = account_balances.fetch((account_id1,)).await?;
let value2 = account_balances.fetch((account_id2,)).await?;

// Entries can be decoded into the static type given by the address:
let result = value1.decode()?;
// Or they can be decoded into any arbitrary shape:
let result = value1.decode_as::<scale_value::Value>()?;
// Or we can "visit" the entry for more control over decoding:
let result = value1.visit(my_visitor)?;
// Or we can just get the bytes out and do what we want:
let result_bytes = value1.bytes();


//// Iterating

// We can iterate over the same entry we fetched things from:
let mut balances = account_balances.iter(()).await?;
while let Some(Ok(entry)) = all_balances.next().await {
    let key = entry.key()?;
    let value = entry.value();

    // Decode the keys that can be decoded:
    let keys_tuple = key.decode()?;
    // Value is as above:
    let value = value.decode()?;

    println!("Keys decoded: {:?}", keys_tuple);
    println!("Key: 0x{}", hex::encode(key.bytes()));
    println!("Value: {:?}", value);
}

This is perhaps the largest change to any specific set of APIs in terms of differences. Take a look at the API docs and the storage example and PR for more on this.

Runtime updates

Before

In previous versions of Subxt, you could subscribe to runtime updates and have Subxt update its internal metadata in response to them, allowing it to track the head of a chain over runtime changes, like so:

let api = OnlineClient::<PolkadotConfig>::new().await?;

// The "easy" approach to ensuring Subxt remains up to date:
let updater = api.updater();
tokio::spawn(async move {
    update_task.perform_runtime_updates().await;
});

// We can also do something lower level:
let updater = api.updater();
tokio::spawn(async move {
    let mut update_stream = updater.runtime_updates().await.unwrap();
    while let Ok(update) = update_stream.next().await {
        let version = update.runtime_version().spec_version;
        match updater.apply_update(update) {
            Ok(()) => {
                println!("Upgrade to version: {} successful", version)
            }
            Err(e) => {
                println!("Upgrade to version {} failed {:?}", version, e);
            }
        };
    }
});

After

The way that Subxt works with metadata across runtimes has been overhauled, and so now Subxt can automatically store and use whichever metadata version is required for a given block, without any need to explicitly monitor for changes. Thus, this code can be safely removed as it is no longer needed.

If you'd like to keep track of when runtime updates occur, you can still do this by simply subscribing to blocks, like so:

let mut blocks = api.stream_blocks().await?;
while let Some(block) = blocks.next().await {
    let block = block?;
    let at_block = block.at().await?;

    // If this changes, then it means that the runtime has updated.
    let spec_version = at_block.spec_version();
}

Dynamic values

Before

Dynamic values were always constructed using and returning scale_value::Values, for instance:

let constant_query = subxt::dynamic::constant(
    "System", 
    "BlockLength"
);

let runtime_api_payload = subxt::dynamic::runtime_api_call(
    "AccountNonceApi",
    "account_nonce",
    vec![Value::from_bytes(account)],
);

let storage_query = subxt::dynamic::storage(
    "System", 
    "Account", 
    vec![Value::from_bytes(account)]
);

After

The dynamic methods have been made more generic, allowing more arbitrary types to be used in their construction, and allowing the return type to be set. This does however mean that types need to be provided sometimes:

let constant_query = subxt::dynamic::constant::<Value>(
    "System", 
    "BlockLength"
);

let runtime_api_payload = subxt::dynamic::runtime_api_call::<_, Value>(
    "AccountNonceApi",
    "account_nonce",
    vec![Value::from_bytes(account)],
);
// We can provide more generic input args now, negating the need 
// to convert to Values unnecessarily:
let runtime_api_payload = subxt::dynamic::runtime_api_call::<_, Value>(
    "AccountNonceApi",
    "account_nonce",
    (account,),
);

// We no longer provide the keys up front for storage; we just point
// to the _entry_ we want and provide the key and return types:
let storage_query = subxt::dynamic::storage::<Vec<Value>, Value>(
    "System", 
    "Account",
);
// This allows us to set better key/value types if we know what to expect. Here
// we know what information we want from account info and the key format:
#[derive(scale_decode::DecodeAsType)]
struct MyAccountInfo {
    nonce: u32,
    data: MyAccountInfoData
}
#[derive(scale_decode::DecodeAsType)]
struct MyAccountInfoData {
    free: u128,
    reserved: u128
}
let storage_query = subxt::dynamic::storage::<(AccountId32,), MyAccountInfo>(
    "System", 
    "Account",
);

Notes:

• As before when scale_value::Value was used everywhere, the actual values provided are always checked at runtime against the API and invalid shapes/values will lead to an error.
• Now, it's possible to provide statically typed values when you know roughly what to expect, or even to just provide your own dynamic value type that isn't scale_value::Value. This makes it easier to work against historic blocks where you may not have or want to use the #[subxt] codegen, but still want to work with static types as much as possible.

Metadata

Subxt previously exposed subxt::Metadata, which was a wrapped version of subxt_metadata::Metadata. The wrapping was removed, and now we have only subxt_metadata::Metadata, which is exposed as subxt::Metadata. This metadata can be cloned but is not cheap to clone, and so we also expose subxt::ArcMetadata, which is used in many places and is the Arc-wrapped version of it, for cheap cloning.

subxt_metadata::Metadata now exposes helper functions to construct it from various frame_metadata versions, to support our historic decoding efforts:

• Metadata::from_v16(..)
• Metadata::from_v15(..)
• Metadata::from_v14(..)
• Metadata::from_v13(..)
• Metadata::from_v12(..)
• Metadata::from_v11(..)
• Metadata::from_v10(..)
• Metadata::from_v9(..)
• Metadata::from_v8(..)

Where the older versions require type information to be provided in addition to the corresponding frame_metadata version.

A list of the main change PRs follows:

Added

• Allow passing $OUT_DIR in the runtime_metadata_path attribute (#2142)
• feat: Add system_chainType to legacy rpcs (#2116)
• Add --at-block option to CLI tool to download metadata at a specific block (#2079)

Changed

• Upgrade to frame-decode 0.17: remove extrinsic encode logic and use from there (#2177)
• [v0.50.0] Implement support for historic blocks in Subxt (#2131)
• subxt-historic: 0.0.8 release: expose type resolver that can be used with visitors (#2140)
• subxt-historic: 0.0.7 release: expose ClientAtBlock bits (#2138)
• subxt-historic: 0.0.6 release: expose metadata at a given block (#2135)
• [v0.50.0] Merge preliminary work to master (#2127)
  • subxt-historic: 0.0.6 release: visit methods (#2126)
  • Allow visiting extrinsic fields in subxt_historic (#2124)
  • Convert historic metadata to subxt::Metadata (#2120)
  • Update scale-info-legacy and frame-decode to latest (#2119)
  • Integrate frame-decode, redo storage APIs and break up Error (#2100)
• Bump smoldot / smoldot-light to latest (#2110)
• [subxt-historic]: extract call and event types from metadata at a block (#2095)
• subxt-historic: add support for returning the default values of storage entries (#2072)

This release version is a deliberately large bump up from 0.44.0 to signify the extent of the changes in this release.

The headline changes are as follows:

• Subxt is no longer head-of-chain only, and can work with historic blocks, all the way back to genesis. Note: user-provided type information is required to do this for very old (> ~2year old, ie pre-V14 metadata) blocks.
• The MVP subxt-historic crate has been removed, its functionality having been merged into Subxt.
• The subxt-core crate has been removed for now to make way for the above. Subxt itself continues to support WASM use cases.
  • For truly no-std functionality, the frame-decode crate now contains much of the underlying logic used throughout Subxt to encode and decode things, and we would like to expand the functionality here.
  • We would like feedback from any users of the subxt-core crate on how they use it, and will use this feedback to drive future work in this area.
• No more monitoring for runtime updates is needed; Subxt now works across different runtime versions automatically.
• Errors are no longer one big Error enum; instead different Subxt APIs return different errors, to limit the number of possible errors in any one place. These all convert into subxt::Error so this can continue to be used as a catch-all.
• Storage APIs have been redone, fixing some issues and giving much more control over iteration, as well as key and value decoding.

There are also a couple of organizational changes which aren't visible:

• We now follow the name.rs + name/submodule.rs convention instead of the name/mod.rs + name/submodule.rs convention.
• CI and testing updates hopefully ensure better organization and coverage with a greater number of different feature flags being tested.

This changes have results in many breaking changes across APIs, which I will try my best to summarize below.

A good place to look for a more holistic understanding of what's changes are the examples, both:

• The smaller single-file examples
• The larger project-based examples

For the smaller examples, start with the basic transaction submission example and then have a look at the blocks example and the storage example to give the best broad overview of the changes. Pick and choose others next depending on what suits.

A breakdown of the significant changes follows, to aid migration efforts:

Configuration

Before

Configuration (PolkadotConfig and SubstrateConfig) was type-only and didn't exist at the value level, and so you'd provide it to the client like so:

use subxt::{OnlineClient, PolkadotConfig};

let api = OnlineClient::<PolkadotConfig>::new().await?;

After

Configuration now exists at the value level too. This is because it has been extended with support for historic types and working with historic metadatas and spec versions. The same code as above will continue to work, but it's now possible to instantiate and tweak the configuration and then use _with_config methods to provide it, like so:

use subxt::{OnlineClient, PolkadotConfig};

let config = PolkadotConfig::builder()
    .use_historic_types(false)
    .build();
let api = OnlineClient::<PolkadotConfig>::new_with_config(config).await?;

The rules for when to use PolkadotConfig and SubstrateConfig remain the same:

• Use PolkadotConfig for the Polkadot Relay Chain.
• Use SubstrateConfig by default with other chains.
• You may need to modify the configuration to work with some chains, as before.

See the docs for PolkadotConfig and SubstrateConfig for more. One example to be aware of is that if you want to work with historic blocks with SubstrateConfig, you'll need to instantiate it yourself and provide historic type information before passing it to OnlineClient or OfflineClient.

Configuration: ExtrinsicParams

Aside from the new historic types support, a notable change to the configuration has been the simplification of transaction extensions, previously called ExtrinsicParams in our Config. Now, the type is called TransactionExtensions and the supporting traits have been simplified and named more appropriately (just TransactionExtensions and TransactionExtension), moving to rely more on frame-decode for the core logic. For any users that implement their own transaction extensions, migrating to the new traits is straightforward and I would encourage you to look at how the built-in transaction extensions are implemented for guidance here.

See (see #2177) for more details around this change.

Working at specific blocks

Before

Previously, you'd be able to select (within a limited range) which block to work at with APIs like so:

let api = OnlineClient::<PolkadotConfig>::new().await?;

let constants = api.constants();

let storage = api.storage().at(block_hash).await?;
let storage = api.storage().at_latest().await?;

let events = api.events().at(block_hash).await?;
let events = api.events().at_latest().await?;

let runtime_apis = api.runtime_api().at(block_hash).await?;
let runtime_apis = api.runtime_api().at_latest().await?;

After

Now, the block is selected first, like so:

let api = OnlineClient::<PolkadotConfig>::new().await?;

let constants = api.at_block(block_hash_or_number).await?.constants();
let constants = api.at_current_block().await?.constants();

let storage = api.at_block(block_hash_or_number).await?.storage();
let storage = api.at_current_block().await?.storage();

let events = api.at_block(block_hash_or_number).await?.events();
let events = api.at_current_block().await?.events();

let runtime_apis = api.at_block(block_hash_or_number).await?.runtime_apis();
let runtime_apis = api.at_current_block().await?.runtime_apis();

Notes:

• at_latest has been renamed to at_current_block and, like before, it fetches the current finalized block at the time of calling.
• at_current_block now accepts a block hash or block number, and returns a client that works in the context of that block.
• Constants were not previously retrieved at a given block; Subxt only knew about a single Metadata and so it was unnecessary. Now, constants are retrieved at a specific block like everything else (different blocks may have different Metadatas).
• A small thing: runtime_api() was renamed to runtime_apis() to be consistent with other APIs names.
• .tx() is now callable at a specific block, and uses this block for any account nonce and mortality configuration.

Working with blocks

Before

A .blocks() method accessed block-specific APIs for fetching and subscribing to blocks.

let api = OnlineClient::<PolkadotConfig>::new().await?;

// fetching:
let block = api.blocks().at(block_hash).await?;
let block = api.blocks().at_latest().await?;

// subscribing:
let mut blocks = api.blocks().subscribe_finalized().await?;
while let Some(block) = blocks_sub.next().await {
    let block = block?;

    let extrinsics = block.extrinsics().await?;
    for ext in extrinsics.iter() {
        // See the blocks example for more.
    }
}

After

Now that APIs are largely block-specific up front, we don't need separate APIs for block fetching, and so we move streaming blocks up a level, removing the .blocks() APIs.

let api = OnlineClient::<PolkadotConfig>::new().await?;

// fetching:
let block = api.at_block(block_hash_or_number).await?;
let block = api.at_current_block().await?;

// subscribing:
let mut blocks = api.stream_blocks().await?;
while let Some(block) = blocks_sub.next().await {
    let block = block?;

    // now, we instantiate a client at a given block, which gives back the
    // same thing as api.at_block() and api.at_current_block() does:
    let at_block = block.at().await?;

    let extrinsics = at_block.extrinsics().fetch().await?;
    for ext in extrinsics.iter() {
        // See the blocks example for more.
    }
}

Notes:

• Working with finalized blocks is always the default now, and API names are shortened to make them the easiest/most obvious to use.
• Use .at() at a given block to hand back a full client which can do anything at that block.
• api.blocks().subscribe_finalized() => api.stream_blocks().
• api.blocks().subscribe_best() => api.stream_best_blocks().
• api.blocks().subscribe_all() => api.stream_all_blocks().

Transactions

Before

Transactions were implicitly created at the latest block, and the APIs were disconnected from any particular block:

let api = OnlineClient::<PolkadotConfig>::new().await?;

// Submit an extrinsic, waiting for success.
let events = api
    .tx()
    .sign_and_submit_then_watch_default(&balance_transfer_tx, &from)
    .await?
    .wait_for_finalized_success()
    .await?;

After

Transactions are anchored to a given block but we continue to provide a .tx() method on the client as a shorthand for "create transactions at the current block".

let api = OnlineClient::<PolkadotConfig>::new().await?;

// Work at a specific block:
let at_block = api.at_current_block().await?;

// Submit the balance transfer extrinsic anchored at this block:
let events = at_block
    .tx()
    .sign_and_submit_then_watch_default(&balance_transfer_tx, &from)
    .await?
    .wait_for_finalized_success()
    .await?;

// A shorthand for the above:
let events = api
    .tx()
    .await? // This is the minimal change from the old APIs.
    .sign_and_submit_then_watch_default(&balance_transfer_tx, &from)
    .await?
    .wait_for_finalized_success()
    .await?;

Notes:

• SignableTransaction::signer_payload, SignableTransaction::sign and SignableTransaction::sign_with_account_and_signature now may return an error (which previously would have led to harder to diagnose issues), and the SignableTransaction type now has a lifetime (see #2177).
• We now use transactions instead of tx everywhere to align better with other API names, but continue to provide tx as a shorthand.
• The word partial is changed to signable in transaction APIs. "partial" was always a confusing name, and "signable" makes it much clearer what is being created; something that can be signed.
  • tx().create_partial_offline(..) => tx().create_signable_offline(..)
  • tx().create_v4_partial_offline(..) => tx().create_v4_signable_offline(..)
  • tx().create_v5_partial_offline(..) => tx().create_v5_signable_offline(..)
  • tx().create_partial(..) => tx().create_signable(..)
  • tx().create_v4_partial(..) => tx().create_v4_signable(..)
  • tx().create_v5_partial(..) => tx().create_v5_signable(..)
• tx().from_bytes(bytes) is added as an easy way to hand a pre-constructed transaction to Subxt to be submitted, removing the need for an ugly SubmittableTransaction::from_bytes method.

Storage Entries

Before

The codegen dealt with the heavy lifting of iterating storage maps at various depths (albeit with a bug), and on fetching an entry you had little control over how you handled the resulting bytes.

let api = OnlineClient::<PolkadotConfig>::new().await?;

//// Fetching:
let result = api
    .storage()
    .at_latest()
    .await?
    .fetch(&storage_query)
    .await?;

//// Iterating
let mut results = api
    .storage()
    .at_latest()
    .await?
    .iter(storage_query)
    .await?;
while let Some(Ok(kv)) = results.next().await {
    println!("Keys decoded: {:?}", kv.keys); // <- Broken in some cases
    println!("Key: 0x{}", hex::encode(&kv.key_bytes));
    println!("Value: {:?}", kv.value);
}

After

A redesign of the Storage APIs makes everything more unified, and allows working at specific storage entries in a much more flexible way than before, while moving logic out of the codegen, simplifying it, and into Subxt proper.

let api = OnlineClient::<PolkadotConfig>::new().await?;
let at_block = api.at_current_block().await?;

let account_balances = at_block
    .storage()
    .entry(storage_query)?;

//// Fetching:

// We can fetch multiple values from an entry:
let value1 = account_balances.fetch((account_id1,)).await?;
let value2 = account_balances.fetch((account_id2,)).await?;

// Entries can be decoded into the static type given by the address:
let result = value1.decode()?;
// Or they can be decoded into any arbitrary shape:
let result = value1.decode_as::<scale_value::Value>()?;
// Or we can "visit" the entry for more control over decoding:
let result = value1.visit(my_visitor)?;
// Or we can just get the bytes out and do what we want:
let result_bytes = value1.bytes();


//// Iterating

// We can iterate over the same entry we fetched things from:
let mut balances = account_balances.iter(()).await?;
while let Some(Ok(entry)) = all_balances.next().await {
    let key = entry.key()?;
    let value = entry.value();

    // Decode the keys that can be decoded:
    let keys_tuple = key.decode()?;
    // Value is as above:
    let value = value.decode()?;

    println!("Keys decoded: {:?}", keys_tuple);
    println!("Key: 0x{}", hex::encode(key.bytes()));
    println!("Value: {:?}", value);
}

This is perhaps the largest change to any specific set of APIs in terms of differences. Take a look at the API docs and the storage example and PR for more on this.

Runtime updates

Before

In previous versions of Subxt, you could subscribe to runtime updates and have Subxt update its internal metadata in response to them, allowing it to track the head of a chain over runtime changes, like so:

let api = OnlineClient::<PolkadotConfig>::new().await?;

// The "easy" approach to ensuring Subxt remains up to date:
let updater = api.updater();
tokio::spawn(async move {
    update_task.perform_runtime_updates().await;
});

// We can also do something lower level:
let updater = api.updater();
tokio::spawn(async move {
    let mut update_stream = updater.runtime_updates().await.unwrap();
    while let Ok(update) = update_stream.next().await {
        let version = update.runtime_version().spec_version;
        match updater.apply_update(update) {
            Ok(()) => {
                println!("Upgrade to version: {} successful", version)
            }
            Err(e) => {
                println!("Upgrade to version {} failed {:?}", version, e);
            }
        };
    }
});

After

The way that Subxt works with metadata across runtimes has been overhauled, and so now Subxt can automatically store and use whichever metadata version is required for a given block, without any need to explicitly monitor for changes. Thus, this code can be safely removed as it is no longer needed.

If you'd like to keep track of when runtime updates occur, you can still do this by simply subscribing to blocks, like so:

let mut blocks = api.stream_blocks().await?;
while let Some(block) = blocks.next().await {
    let block = block?;
    let at_block = block.at().await?;

    // If this changes, then it means that the runtime has updated.
    let spec_version = at_block.spec_version();
}

Dynamic values

Before

Dynamic values were always constructed using and returning scale_value::Values, for instance:

let constant_query = subxt::dynamic::constant(
    "System", 
    "BlockLength"
);

let runtime_api_payload = subxt::dynamic::runtime_api_call(
    "AccountNonceApi",
    "account_nonce",
    vec![Value::from_bytes(account)],
);

let storage_query = subxt::dynamic::storage(
    "System", 
    "Account", 
    vec![Value::from_bytes(account)]
);

After

The dynamic methods have been made more generic, allowing more arbitrary types to be used in their construction, and allowing the return type to be set. This does however mean that types need to be provided sometimes:

let constant_query = subxt::dynamic::constant::<Value>(
    "System", 
    "BlockLength"
);

let runtime_api_payload = subxt::dynamic::runtime_api_call::<_, Value>(
    "AccountNonceApi",
    "account_nonce",
    vec![Value::from_bytes(account)],
);
// We can provide more generic input args now, negating the need 
// to convert to Values unnecessarily:
let runtime_api_payload = subxt::dynamic::runtime_api_call::<_, Value>(
    "AccountNonceApi",
    "account_nonce",
    (account,),
);

// We no longer provide the keys up front for storage; we just point
// to the _entry_ we want and provide the key and return types:
let storage_query = subxt::dynamic::storage::<Vec<Value>, Value>(
    "System", 
    "Account",
);
// This allows us to set better key/value types if we know what to expect. Here
// we know what information we want from account info and the key format:
#[derive(scale_decode::DecodeAsType)]
struct MyAccountInfo {
    nonce: u32,
    data: MyAccountInfoData
}
#[derive(scale_decode::DecodeAsType)]
struct MyAccountInfoData {
    free: u128,
    reserved: u128
}
let storage_query = subxt::dynamic::storage::<(AccountId32,), MyAccountInfo>(
    "System", 
    "Account",
);

Notes:

• As before when scale_value::Value was used everywhere, the actual values provided are always checked at runtime against the API and invalid shapes/values will lead to an error.
• Now, it's possible to provide statically typed values when you know roughly what to expect, or even to just provide your own dynamic value type that isn't scale_value::Value. This makes it easier to work against historic blocks where you may not have or want to use the #[subxt] codegen, but still want to work with static types as much as possible.

Metadata

Subxt previously exposed subxt::Metadata, which was a wrapped version of subxt_metadata::Metadata. The wrapping was removed, and now we have only subxt_metadata::Metadata, which is exposed as subxt::Metadata. This metadata can be cloned but is not cheap to clone, and so we also expose subxt::ArcMetadata, which is used in many places and is the Arc-wrapped version of it, for cheap cloning.

subxt_metadata::Metadata now exposes helper functions to construct it from various frame_metadata versions, to support our historic decoding efforts:

• Metadata::from_v16(..)
• Metadata::from_v15(..)
• Metadata::from_v14(..)
• Metadata::from_v13(..)
• Metadata::from_v12(..)
• Metadata::from_v11(..)
• Metadata::from_v10(..)
• Metadata::from_v9(..)
• Metadata::from_v8(..)

Where the older versions require type information to be provided in addition to the corresponding frame_metadata version.

A list of the main change PRs follows:

Added

• Allow passing $OUT_DIR in the runtime_metadata_path attribute (#2142)
• feat: Add system_chainType to legacy rpcs (#2116)
• Add --at-block option to CLI tool to download metadata at a specific block (#2079)

Changed

• Upgrade to frame-decode 0.17: remove extrinsic encode logic and use from there (#2177)
• [v0.50.0] Implement support for historic blocks in Subxt (#2131)
• subxt-historic: 0.0.8 release: expose type resolver that can be used with visitors (#2140)
• subxt-historic: 0.0.7 release: expose ClientAtBlock bits (#2138)
• subxt-historic: 0.0.6 release: expose metadata at a given block (#2135)
• [v0.50.0] Merge preliminary work to master (#2127)
  • subxt-historic: 0.0.6 release: visit methods (#2126)
  • Allow visiting extrinsic fields in subxt_historic (#2124)
  • Convert historic metadata to subxt::Metadata (#2120)
  • Update scale-info-legacy and frame-decode to latest (#2119)
  • Integrate frame-decode, redo storage APIs and break up Error (#2100)
• Bump smoldot / smoldot-light to latest (#2110)
• [subxt-historic]: extract call and event types from metadata at a block (#2095)
• subxt-historic: add support for returning the default values of storage entries (#2072)

Update to frame-decode 0.17.1 and update CHANGELOG with frame-decode …

Update copyright headers to 2026

[0.44.2] - 2026-01-09

This manually cherry-picks #2142 onto the 0.44 branch to allow using $OUT_DIR in a couple of Subxt macro attributes.

Changed

• Allow passing $OUT_DIR in the runtime_metadata_path attribute #2142

[0.44.1] - 2026-01-08

When using .tip_of(some_tip, optional_asset_id) to configure a tip for transactions, the actual tip was being set to 0. This is now fixed.

Fixed

• Fix tipping for ChargeAssetTxPayment tx extension(#2151)

[0.44.0] - 2025-08-28

This small release primarily fixes a few issues, but also adds the code for a prelease of subxt-historic, a new crate (at the moment) for working with historic blocks and state. Future releases will aim to stabilize this crate to the level of other subxt crates or otherwise merge the logic into subxt itself.

This is a minor version bump because, in theory at least, adding the Clone bound to block headers in (#2047) is a breaking change, although I think it is unlikely that this will impact any users.

Added

• Add prerelease subxt-historic crate for accessing historic (non head-of-chain) blocks (#2040)

Changed

• Block: Implement clone (#2047)
• Increase number of dev accounts (#2068)

Fixed

• Do not panic when encoding call data with invalid fields (#2070)
• Tweak test to reduce chance of failure, and need jsonrpsee/server for tests (#2057)
• Fix 1.89 clippy warnings (#2055)
• Increase reconnecting client request/response size (#2046)

This small release primarily fixes a few issues, but also adds the code for a prelease of subxt-historic, a new crate (at the moment) for working with historic blocks and state. Future releases will aim to stabilize this crate to the level of other subxt crates or otherwise merge the logic into subxt itself.

This is a minor version bump because, in theory at least, adding the Clone bound to block headers in (#2047) is a breaking change, although I think it is unlikely that this will impact any users.

Added

• Add prerelease subxt-historic crate for accessing historic (non head-of-chain) blocks (#2040)

Changed

• Block: Implement clone (#2047)
• Increase number of dev accounts (#2068)

Fixed

• Do not panic when encoding call data with invalid fields (#2070)
• Tweak test to reduce chance of failure, and need jsonrpsee/server for tests (#2057)
• Fix 1.89 clippy warnings (#2055)
• Increase reconnecting client request/response size (#2046)

[0.43.0] - 2025-07-17

This is a reasonably small release which is mainly bug fixing, but has a couple of changes I'd like to elaborate on:

Remove codec::Encode and codec::Decode derives from generated APIs by default (#2008)

When generating an API using the #[subxt::subxt(...)] macro (or programatically via subxt-codegen), we had always previously added parity_scale_codec::Encode and parity_scale_codec::Decode derives to all of the generated types. Most places in Subxt have not made use of these for a long time (relying instead on scale_encode::EncodeAsType and scale_decode::DecodeAsType, since they allow encoding and encoding which takes the type information into account and can more gracefully handle incompatibilities).

We eventually hit an issue to which the most appropriate fix was just to remove these derives.

If you still need the parity_scale_codec::Encode or parity_scale_codec::Decode derives on certain types, you have two options:

1. Use the derive_for_type attr to add them back where needed, eg:

   #[subxt::subxt(
     ...
     derive_for_type(
       path = "staging_xcm::v3::multilocation::MultiLocation",
       derive = "parity_scale_codec::Encode, parity_scale_codec::Decode",
       recursive
     )
   )]

2. Use the derive_for_all_types attr to add them back everywhere, eg:

   #[subxt::subxt(
     ...
     derive_for_all_types = "parity_scale_codec::Encode, parity_scale_codec::Decode"
   )]
   

Prefer (1) where possible to reduce the amount of generated code, and reduce the likelihood of running into issues around those derives in certain edge cases.

This PR changes some things around storage keys to remove one last requirement for Encode and Decode derives, and also as a side effect changes api.storage().call_raw() slightly to no longer also try to decode the resulting type via Decode, leaving this to the user (and also meaning it's much easier now for the user to obtain the raw bytes for some storage entry).

In other words, instead of doing something like:

let (compact_len, metadata) = rt
        .call_raw::<(Compact<u32>, frame_metadata::RuntimeMetadataPrefixed)>(
            "Metadata_metadata",
            None,
        )
        .await?;

You would now do:

let meta_bytes = rt.call_raw("Metadata_metadata", None).await?;
let (compact_len, metadata): (Compact<u32>, frame_metadata::RuntimeMetadataPrefixed) =
    Decode::decode(&mut &*meta_bytes)?;

Address some issues around tx mortality (#2025)

Prior to this change, the intended behavior was that any transaction submitted via an OnlineClient would have a mortality of 32 blocks by default, and any transaction submitted via an OfflineClient would be immortal by default. A couple of issues were present or cropped up however:

• If you explicitly configure the mortality via setting params like PolkadotExtrinsicParamsBuilder::new().mortal(32).build(), the OfflineClient transaction would still be immortal, because it didn't have enough information to properly configure the mortality as asked for (by virtue of being offline and unable to fetch it).
• The intended behaviour turned out to have been broken, and transactions were being submitted as immortal even via the OnlineClient by default, unless mortality was explicitly configured.
• There was no easy way to actually set the mortality for an OfflineClient transaction; you'd have to do something like this:

  let params = DefaultExtrinsicParamsBuilder::new();
  params.5 = CheckMortalityParams::mortal_from_unchecked(for_n_blocks, from_block_n, from_block_hash);

With this PR, transactions are now mortal by default using the OnlineClient, we now return an error if you try to construct a transaction with the OfflineClient and try to use params.mortal(..) when configuring it, and we expose params.mortal_from_unchecked(..) to allow configuration for offline transactions without the ugly code above.

In this PR, we also discovered an issue decoding Eras and fixed this, so that decoding the mortality of a transaction when it is mortal should now work.

Add FFI example (#2037)

I'd like to do a quick shoutout to @wassimans, who submitted an excellent example for how to interact with Subxt via the C FFI in Python and Node.JS. This is something I've wanted to add for a while, so it's lovely to see this new example which highlights one of the strengths of Subxt over Javascript based compatitors in the space.

All of the non-trivial changes in this release are listed below:

Added

• Add FFI example (#2037)

Changed

• Remove codec::Encode and codec::Decode derives from generated APIs by default (#2008)
• Address some issues around tx mortality (#2025)

Fixed

• Fix 'subxt explore storage': don't turn keys to bytes (#2038)
• Refactor: improve nonce and block injection in extrinsic params (#2032)
• Improve docs for at_latest (#2035)
• Clippy fixes for latest Rustc (#2033)
• docs: fix minor comment typos (#2027)
• chore: remove redundant backtick in comment (#2020)
• Keep codec attrs even when Encode/Decode not used (#2023)
• Run CI on v0.N.x branches or PRs to them for ease of backporting (#2017)
• De-dup types early in CLI/macro so that derives/substitutes work for de-duped types (#2015)
• If only one hasher, always treat any key as a single and not NMap key, even if it's a tuple. (#2010)

This is a reasonably small release which is mainly bug fixing, but has a couple of changes I'd like to elaborate on:

Remove codec::Encode and codec::Decode derives from generated APIs by default (#2008)

When generating an API using the #[subxt::subxt(...)] macro (or programatically via subxt-codegen), we had always previously added parity_scale_codec::Encode and parity_scale_codec::Decode derives to all of the generated types. Most places in Subxt have not made use of these for a long time (relying instead on scale_encode::EncodeAsType and scale_decode::DecodeAsType, since they allow encoding and encoding which takes the type information into account and can more gracefully handle incompatibilities).

We eventually hit an issue to which the most appropriate fix was just to remove these derives.

If you still need the parity_scale_codec::Encode or parity_scale_codec::Decode derives on certain types, you have two options:

1. Use the derive_for_type attr to add them back where needed, eg:

   #[subxt::subxt(
     ...
     derive_for_type(
       path = "staging_xcm::v3::multilocation::MultiLocation",
       derive = "parity_scale_codec::Encode, parity_scale_codec::Decode",
       recursive
     )
   )]
   

2. Use the derive_for_all_types attr to add them back everywhere, eg:

   #[subxt::subxt(
     ...
     derive_for_all_types = "parity_scale_codec::Encode, parity_scale_codec::Decode"
   )]
   

Prefer (1) where possible to reduce the amount of generated code, and reduce the likelihood of running into issues around those derives in certain edge cases.

This PR changes some things around storage keys to remove one last requirement for Encode and Decode derives, and also as a side effect changes api.storage().call_raw() slightly to no longer also try to decode the resulting type via Decode, leaving this to the user (and also meaning it's much easier now for the user to obtain the raw bytes for some storage entry).

In other words, instead of doing something like:

let (compact_len, metadata) = rt
        .call_raw::<(Compact<u32>, frame_metadata::RuntimeMetadataPrefixed)>(
            "Metadata_metadata",
            None,
        )
        .await?;

You would now do:

let meta_bytes = rt.call_raw("Metadata_metadata", None).await?;
let (compact_len, metadata): (Compact<u32>, frame_metadata::RuntimeMetadataPrefixed) =
    Decode::decode(&mut &*meta_bytes)?;

Address some issues around tx mortality (#2025)

Prior to this change, the intended behavior was that any transaction submitted via an OnlineClient would have a mortality of 32 blocks by default, and any transaction submitted via an OfflineClient would be immortal by default. A couple of issues were present or cropped up however:

• If you explicitly configure the mortality via setting params like PolkadotExtrinsicParamsBuilder::new().mortal(32).build(), the OfflineClient transaction would still be immortal, because it didn't have enough information to properly configure the mortality as asked for (by virtue of being offline and unable to fetch it).
• The intended behaviour turned out to have been broken, and transactions were being submitted as immortal even via the OnlineClient by default, unless mortality was explicitly configured.
• There was no easy way to actually set the mortality for an OfflineClient transaction; you'd have to do something like this:

  let params = DefaultExtrinsicParamsBuilder::new();
  params.5 = CheckMortalityParams::mortal_from_unchecked(for_n_blocks, from_block_n, from_block_hash);
  

With this PR, transactions are now mortal by default using the OnlineClient, we now return an error if you try to construct a transaction with the OfflineClient and try to use params.mortal(..) when configuring it, and we expose params.mortal_from_unchecked(..) to allow configuration for offline transactions without the ugly code above.

In this PR, we also discovered an issue decoding Eras and fixed this, so that decoding the mortality of a transaction when it is mortal should now work.

Add FFI example (#2037)

I'd like to do a quick shoutout to @wassimans, who submitted an excellent example for how to interact with Subxt via the C FFI in Python and Node.JS. This is something I've wanted to add for a while, so it's lovely to see this new example which highlights one of the strengths of Subxt over Javascript based compatitors in the space.

All of the non-trivial changes in this release are listed below:

Added

• Add FFI example (#2037)

Changed

• Remove codec::Encode and codec::Decode derives from generated APIs by default (#2008)
• Address some issues around tx mortality (#2025)

Fixed

• Fix 'subxt explore storage': don't turn keys to bytes (#2038)
• Refactor: improve nonce and block injection in extrinsic params (#2032)
• Improve docs for at_latest (#2035)
• Clippy fixes for latest Rustc (#2033)
• docs: fix minor comment typos (#2027)
• chore: remove redundant backtick in comment (#2020)
• Keep codec attrs even when Encode/Decode not used (#2023)
• Run CI on v0.N.x branches or PRs to them for ease of backporting (#2017)
• De-dup types early in CLI/macro so that derives/substitutes work for de-duped types (#2015)
• If only one hasher, always treat any key as a single and not NMap key, even if it's a tuple. (#2010)

This patch release reduces the rust-version to 1.85.0, given that we don't use any features newer than this at the moment.

The primary benefit of this release is introducing support for the about-to-be-stabilised-in-polkadot-sdk V16 metadata, and with that, support for calling Pallet View Functions on runtimes which will support this. Pallet View Functions are used much like Runtime APIs, except that they are declared in specific pallets and not declared at the runtime-wide level, allowing pallets to carry their own APIs with them.

Pallet View Functions

Calling a Pallet View Function in this Subxt release will look like:

use runtime::proxy::view_functions::check_permissions::{Call, ProxyType};

// Construct the call, providing the two arguments.
let view_function_call = runtime::view_functions()
    .proxy()
    .check_permissions(
        Call::System(runtime::system::Call::remark { remark: b"hi".to_vec() }),
        ProxyType::Any
    );

// Submit the call and get back a result.
let _is_call_allowed = api
    .view_functions()
    .at_latest()
    .await?
    .call(view_function_call)
    .await?;

Like Runtime APIs and others, the dynamic API can also be used to call into Pallet View Functions, which has the advantage of not needing the statically generated interface, but the downside of not being strongly typed. This looks like the following:

use scale_value::value;

let metadata = api.metadata();

// Look up the query ID for the View Function in the node metadata:
let query_id = metadata
    .pallet_by_name("Proxy")
    .unwrap()
    .view_function_by_name("check_permissions")
    .unwrap()
    .query_id();

// Construct the call, providing the two arguments.
let view_function_call = subxt::dynamic::view_function_call(
    *query_id,
    vec![
        value!(System(remark(b"hi".to_vec()))), 
        value!(Any())
    ],
);

// Submit the call and get back a result.
let _is_call_allowed = api
    .view_functions()
    .at_latest()
    .await?
    .call(view_function_call)
    .await?;

Updated Config trait

Another change to be aware of is that our Config trait has been tweaked. The Hash associated type is no longer needed, as it can be obtained via the Hasher associated type already, and PolkadotConfig/SubstrateConfig now set the hasher by default to be DynamicHasher256, which will (when V16 metadata is available for a runtime) automatically select between Keccak256 and BlakeTwo256 hashers depending on what the chain requires.

Other changes

We also solidify our support for V1 archive RPCs, upgrade the codebase to Rust 2024 edition, and a bunch of other changes, the full list of which is here:

Added

• Support v16 metadata and use it by default if it's available (#1999)
• Metadata V16: Implement support for Pallet View Functions (#1981)
• Metadata V16: Be more dynamic over which hasher is used. (#1974)

Changed

• Update to 2024 edition (#2001)
• Update Smoldot to latest version (#1991)
• Update native test timeout to 45 mins (#2002)
• chore(deps): tokio ^1.44.2 (#1989)
• Add DefaultParams to allow more transaction extensions to be used when calling _default() methods (#1979)
• Use wat instead of wabt to avoid CI cmake error (and use supported dep) (#1980)
• Support v1 archive RPCs (#1977)
• Support V16 metadata and refactor metadata code (#1967)
• Allow submitting transactions ignoring follow events (#1962)
• Improve error message regarding failure to extract metadata from WASM runtime (#1961)
• Add docs for subxt-rpcs and fix example (#1954)

Fixed

• Fix CLI storage diff (#1958)
• chore: fix some typos (#1997)

This release makes two main changes:

Add subxt-rpcs crate.

Previously, if you wanted to make raw RPC calls but weren't otherwise interested in using the higher level Subxt interface, you still needed to include the entire Subxt crate.

Now, one can depend on subxt-rpcs directly. This crate implements the new RPC-V2 chainHead/transaction endpoints as well as the currently unstable archive endpoints. it also implements various legacy endpoints that Subxt uses as a fallback to the modern ones. It also provides several feature gated clients for interacting with them:

• jsonrpsee: A jsonrpsee based RPC client for connecting to individual RPC nodes.
• unstable-light-client: A Smoldot based light client which connects to multiple nodes in chains via p2p and verifies everything handed back, removing the need to trust any individual nodes.
• reconnecting-rpc-client: Another jsonrpsee based client which handles reconnecting automatically in the event of network issues.
• mock-rpc-client: A mock RPC client that can be used in tests.

Custom clients can be implemented if preferred.

Example usage via jsonrpsee feature:

use subxt_rpcs::{RpcClient, ChainHeadRpcMethods};

// Connect to a local node:
let client = RpcClient::from_url("ws://127.0.0.1:9944").await?;
// Use chainHead/archive V2 methods:
let methods = ChainHeadRpcMethods::new(client);

// Call some RPC methods (in this case a subscription):
let mut follow_subscription = methods.chainhead_v1_follow(false).await.unwrap();
while let Some(follow_event) = follow_subscription.next().await {
    // do something with events..
}

Support creating V5 transactions.

Subxt has supported decoding V5 transactions from blocks since 0.38.0, but now it also supports constructing V5 transactions where allowed. Some naming changes have also taken place to align with the Substrate terminology now around transactions (see #1931 for more!).

The main changes here are:

• subxt_core now contains versioned methods for creating each of the possible types of transaction (V4 unsigned, V4 signed, V5 "bare" or V5 "general"), enabling the APIs to be tailored for each case.
• subxt exposes higher level wrappers these (ie api.tx().create_v4_unsigned(..), api.tx().create_v5_bare(..)), but also continues to expose the same standard APIs for creating transactions which will, under the hood, decide what to create based on the chain we're connected to.
• APIs like sign_and_submit now take a T::AccountId rather than a T::Address since it was found to not be useful to provide the latter, and V5 transactions only expect an T::AccountId.
• Signed Extensions are now referred to as Transaction Extensions, and we've tweaked the interface around how these work slightly to accomodate the fact that in V5 transactions, the signature is passed into a transaction extension where applicable (VerifySignature).
• As a side effect, it's simpler to set mortality on transactions; no more block hash needs to be provided; only the number of blocks you would like a transaction to live for.

A full list of the relevant changes is as follows:

Added

• Support constructing and submitting V5 transactions (#1931)
• Add archive RPCs to subxt-rpcs (#1940)
• Document generating interface from Runtime WASM and change feature to runtime-wasm-path (#1936)
• Split RPCs into a separate crate (#1910)

Changed

• Wrap the subxt::events::Events type to avoid exposing subxt_core errors and types unnecessarily (#1948)
• Allow transaction timeout in ChainheadBackend to be configured (#1943)
• refactor: make ExtrinsicEvents::new public for external access (#1933)

This release reverts the usage of the polkadot-sdk umbrella crate, which was causing issues such as an increased number of dependencies in Cargo.lock. For more details, see #1925.

Additionally, this update bumps the Polkadot SDK-related dependencies to their latest versions, ensuring compatibility and stability.

Fixed

• Remove usage of polkadot-sdk umbrella crate (#1926)

Full Changelog: https://github.com/paritytech/subxt/compare/v0.39.0...v0.40.0

This release is mostly bug fixes and changes. The only change that should be a breaking change is removing the substrate-compat feature flag (see #1850), which we'll go into more detail about.

The substrate-compat feature flag has been removed.

The substrate-compat feature flag essentially provided:

1. An implementation of the subxt::config::Header trait for anything implementing sp_runtime::traits::Header (here).
2. Same for subxt::config::Hasher and anything implementing sp_runtime::traits::Hasher (here).
3. A subxt_core::tx::PairSigner type which could be given something implementing sp_core::Pair and then be used to sign transactions (here).
4. From impls for sp_runtime::AccountId32 and related for subxt::utils::AccountId32 (here).
5. Likewise for sp_runtime::MultiAddress and subxt::utils::MultiAddress (here).
6. Likewise for sp_runtime::MultiSignature and subxt::utils::MultiSignature (here).

While useful, providing these features in Subxt is almost impossible to maintain: we can only support a single version of sp_runtime/sp_core at a time, but many versions are in use in the wild. This led to various issues regarding the mismatch between sp_* crates in use and a given version of Subxt. More generally, the goal of Subxt is to be independent from any specific version of Substrate, and communicate via the exposed RPC APIs in order to work across any compatible Substrate version (or indeed, alternative implementations that follow things like the RPC spec).

As a result, we've taken the decision to remove this compatibility layer from Subxt itself. To migrate away from this feature, we suggest:

1. Using the example here to see how to use a Substrate signer to sign Subxt transactions.
2. Looking at subxt_signer instead, if it's a viable alternative in your case.
3. Following the "here" links above to see what impls were removed. Impls can generally be recreated as needed using wrapper types which allow converting between Substrate and Subxt types/traits, for instance:

// Wrap a substrate header type in this to impl the subxt Header trait:
struct SubxtHeader<T>(pub T);

// This basically copies the code removed from Subxt, but on a wrapper type:
impl <T> subxt::config::Header for SubxtHeader<T>
where
    T: sp_runtime::traits::Header,
    <T as sp_runtime::traits::Header>::Number: Into<u64>,
{
    type Number = T::Number;
    type Hasher = T::Hashing;

    fn number(&self) -> Self::Number {
        *self.0.number()
    }
}

The hope is that this pattern is applicable to any such types that you find useful to share between Substrate and Subxt code. Please raise an issue if you can't find a solution in your case, and we'll endeavour to help!

The result of this is that your code will work against whichever Substrate crate versions you are using, at the cost of this code no longer being included behind the substrate-compat feature flag.

A full list of relevant changes and fixes (nothing was added in this release) is as follows:

Changed

• remove substrate compat (#1850)
• migrate custom error trait impls to thiserror (#1856)
• re-export jsonrpsee in subxt::ext (#1843)

Fixed

• don't double hash: use the same hash in ExtrinsicDetails and ExtrinsicDetails (#1917)
• fix and test sr25519 signing in nostd (#1872)
• preserve custom metadata when converting between Subxt metadata and frame_metadata (#1914)
• fix: don't wrap rpc error in DisconnectedWillReconnect in reconnecting rpc client (#1904)
• fix: substrate runner, support new libp2p addr log (#1892)
• update Artifacts (auto-generated) (#1874)
• bump frame-decode and frame-metadata to latest (#1870)
• fix unstable-light-client + ChainHeadBackend tx events (#1865)
• when native feature is enabled, we need polkadot-sdk/std for eg examples to work (#1864)
• load latest metadata version from Wasm blobs. (#1859)
• minor fix - Yew example (#1852)
• update the release notes to work for current releases (#1842)

This release doesn't introduce any substantial breaking changes and focuses primarily on incremental improvements, testing and bug fixes. A few of the highlights include:

• #1785: Support decoding V5 extrinsics in blocks (currently Subxt will still submit V4 extrinsics). This also unifies our extrinsic decoding logic into one place.
• #1802: Stabilizing the subxt::backend::unstable::UnstableBackend (it's now called subxt::backend::chain_head::ChainHeadBackend). This backend can be used to interact with the modern chainHead RPC methods exposed by Smoldot and compliant RPC nodes. See this example.
• #1803: Stabilizing the reconnecting-rpc-client. See this example.
• #1720: A nice little QoL improvement if you have the raw runtime WASM and would like to generate an interface directly from that (ie with #[subx(runtime_path = "path/to/runtime.wasm")]).
• #1661: Support loading keys directly from the PolkadotJS JSON to be used in Subxt.
• #1638: Improve support for Eth style chains by defining a 20-byte account ID type directly in subxt-core. See this example.

The notable changes in this release are as follows:

Added

• add reconnecting tests for unstable_backend (#1765)
• add support for generating metadata from runtime wasm files (#1720)
• support loading keys from Polkadot-JS accounts (#1661)
• allow tx payloads to be boxed (#1690)
• add hash method to ExtrinsicDetails (#1676)
• expose secret_key method for ecdsa::Keypair and eth::Keypair (#1628)
• add 20-byte account id to subxt_core (#1638)

Changed

• make it clearer which extrinsic failed to decode (#1835)
• chore(deps): bump frame-metadata from 16 to 17 (#1836)
• chore(deps): bump scale family crates, primitive-types and impl-serde (#1832)
• chore(deps): replace instant with web-time (#1830)
• deps: use polkadot-sdk umbrella crate (#1786)
• stabilize reconnecting-rpc-client (#1803)
• stabilize chainhead backend (#1802)
• derive serialize on more types (#1797)
• use frame-decode for core extrinsic decode logic (including v5 support) (#1785)
• reconn-rpc-client: parse URL before connecting (#1789)
• update proc_macro_error to proc_macro_error2 (#1767)
• chore(deps): update Smoldot to the latest version (#1400)
• remove unneeded ?Sized bound and replace never type with () (#1758)
• improve test coverage for legacy Backend impl (#1751)
• add integration tests for unstable-reconnecting-rpc-client (#1711)
• replace reconnecting-jsonrpsee-ws-client with subxt-reconnecting-rpc-client (#1705)
• allow PartialExtrinsic to be held across await points (#1658)
• chore(deps): bump jsonrpsee from 0.22.5 to 0.23.1 (#1656)

Fixed

• fix stripping metadata in the case where enums like RuntimeCall are handed back (#1774)
• fix: defalt-feature -> default-features Cargo.toml (#1828)
• avoid hang by notifying subscribers when the backend is closed (#1817)
• fix: error message on rpc errors (#1804)
• docs: fix typos (#1776)
• examples: fix reconnecting logging target (#1733)
• docs: fix spelling issues (#1699)
• chore: fix some comments (#1697)
• codegen: Fix decode error by adding #[codec(dumb_trait_bound)] (#1630)

This release mainly adds support for the sign extension CheckMetadataHash and fixes a regression introduced in v0.36.0 where the type de-duplication was too aggressive and lots of the same type such as BoundedVec was duplicated to plenty of different types such as BoundedVec1, BoundedVec2, .. BoundedVec<N>.

Added

• Implemented sign_prehashed for ecdsa::Keypair and eth::Keypair (#1598)
• Add a basic version of the CheckMetadataHash signed extension (#1590)

Yanked because the typegen changed, it's a breaking change.

This release adds a few new features, which I'll go over below in more detail.

subxt-core

We now have a brand new subxt-core crate, which is #[no-std] compatible, and contains a lot of the core logic that is needed in Subxt. Using this crate, you can do things in a no-std environment like:

• blocks: decode and explore block bodies.
• constants: access and validate the constant addresses in some metadata.
• custom_values: access and validate the custom value addresses in some metadata.
• metadata: decode bytes into the metadata used throughout this library.
• storage: construct storage request payloads and decode the results you'd get back.
• tx: construct and sign transactions (extrinsics).
• runtime_api: construct runtime API request payloads and decode the results you'd get back.
• events: decode and explore events.

Check out the docs for more, including examples of each case.

A breaking change that comes from migrating a bunch of logic to this new crate is that the ExtrinsicParams trait is now handed &ClientState<T> rather than a Client. ClientState is just a concrete struct containing the state that one needs for things like signed extensions.

Support for reconnecting

We've baked in a bunch of support for automatically reconnecting after a connection loss into Subxt. This comes in three parts:

1. An RPC client that is capable of reconnecting. This is gated behind the unstable-reconnecting-rpc-client feature flag at the moment, and
2. Handling in the subxt Backends such that when the RPC client notifies it that it is reconnecting, the backend will transparently handle this behind the scenes, or else pass on a DisconnectedWillReconnect error to the user where it cannot. Note that the individual LegacyRpcMethods and UnstableRpcMethods are not automatically retried on reconnection. Which leads us to..
3. A couple of util helpers (subxt::backend::retry and subxt::backend::retry_stream) which can be used in conjunction with a reconnecting RPC client to make it easy to automatically retry RPC method calls where needed.

We'd love feedback on this reconnecting work! To try it out, enable the unstable-reconnecting-rpc-client feature flag and then you can make use of this like so:

use std::time::Duration;
use futures::StreamExt;
use subxt::backend::rpc::reconnecting_rpc_client::{Client, ExponentialBackoff};
use subxt::{OnlineClient, PolkadotConfig};

// Generate an interface that we can use from the node's metadata.
#[subxt::subxt(runtime_metadata_path = "../artifacts/polkadot_metadata_small.scale")]
pub mod polkadot {}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create a new client with a reconnecting RPC client.
    let rpc = Client::builder()
        // We can configure the retry policy; here to an exponential backoff.
        // This API accepts an iterator of retry delays, and here we use `take`
        // to limit the number of retries.
        .retry_policy(
            ExponentialBackoff::from_millis(100)
                .max_delay(Duration::from_secs(10))
                .take(3),
        )
        .build("ws://localhost:9944".to_string())
        .await?;

    // Use this reconnecting client when instantiating a Subxt client:
    let api: OnlineClient<PolkadotConfig> = OnlineClient::from_rpc_client(rpc.clone()).await?;

Check out the full example here.

Better Ethereum support

We've added built-in support for Ethereum style chains (eg Frontier and Moonbeam) in subxt-signer, making it easier to sign transactions for these chains now.

Check out a full example here.

We plan to improve on this in the future, baking in better Ethereum support if possible so that it's as seamless to use AccountId20 as it is AccountId32.

Stabilizing the new V2 RPCs (#1540, #1539, #1538)

A bunch of the new RPCs are now stable in the spec, and have consequently been stabilized here, bringing the unstable-backend a step closer to being stabilized itself! We'll probably first remove the feature flag and next make it the default backend, in upcoming releases.

All of the notable changes in this release are as follows:

Added

• Add frontier/ethereum example (#1557)
• Rpc: add full support reconnecting rpc client (#1505)
• Signer: ethereum implementation (#1501)
• subxt-core crate (#1466)

Changed

• Bump scale-decode and related deps to latest (#1583)
• Update Artifacts (auto-generated) (#1577)
• Update deps to use scale-type-resolver 0.2 (#1565)
• Stabilize transactionBroadcast methods (#1540)
• Stabilize transactionWatch methods (#1539)
• Stabilize chainHead methods (#1538)
• Rename traits to remove T suffix (#1535)
• Add Debug/Clone/etc for common Configs for convenience (#1542)
• Unstable_rpc: Add transactionBroadcast and transactionStop (#1497)

Fixed

• metadata: Fix cargo clippy (#1574)
• Fixed import in subxt-signer::eth (#1553)
• chore: fix typos and link broken (#1541)
• Make subxt-core ready for publishing (#1508)
• Remove dupe storage item if we get one back, to be compatible with Smoldot + legacy RPCs (#1534)
• fix: substrate runner libp2p port (#1533)
• Swap BinaryHeap for Vec to avoid Ord constraint issue (#1523)
• storage_type: Strip key proper hash and entry bytes (32 instead of 16) (#1522)
• testing: Prepare light client testing with substrate binary and add subxt-test macro (#1507)

This release contains several fixes, adds no_std support to a couple of crates (subxt-signer and subxt-metadata) and introduces a few quality of life improvements, which I'll quickly cover:

Reworked light client (#1475)

This PR reworks the light client interface. The "basic" usage of connecting to a parachain now looks like this:

#[subxt::subxt(runtime_metadata_path = "../artifacts/polkadot_metadata_small.scale")]
pub mod polkadot {}

use subxt::lightclient::LightClient;

// Instantiate a light client with the Polkadot relay chain given its chain spec.
let (lightclient, polkadot_rpc) = LightClient::relay_chain(POLKADOT_SPEC)?;
// Connect the light client to some parachain by giving a chain spec for it.
let asset_hub_rpc = lightclient.parachain(ASSET_HUB_SPEC)?;

// Now, we can create Subxt clients from these Smoldot backed RPC clients:
let polkadot_api = OnlineClient::<PolkadotConfig>::from_rpc_client(polkadot_rpc).await?;
let asset_hub_api = OnlineClient::<PolkadotConfig>::from_rpc_client(asset_hub_rpc).await?;

This interface mirrors the requirement that we must connect to a relay chain before we can connect to a parachain. It also moves the light client specific logic into an RpcClientT implementation, rather than exposing it as a subxt::client::LightClient.

Typed Storage Keys (#1419)

This PR changes the storage interface so that, where possible, we now also decode the storage keys as well as the values when iterating over storage entries:

#[subxt::subxt(runtime_metadata_path = "../artifacts/polkadot_metadata_small.scale")]
pub mod polkadot {}

// Create a new API client, configured to talk to Polkadot nodes.
let api = OnlineClient::<PolkadotConfig>::new().await?;

// Build a storage query to iterate over account information.
let storage_query = polkadot::storage().system().account_iter();

// Get back an iterator of results (here, we are fetching 10 items at
// a time from the node, but we always iterate over one at a time).
let mut results = api.storage().at_latest().await?.iter(storage_query).await?;

while let Some(Ok(kv)) = results.next().await {
    // We used to get a tuple of key bytes + value. Now we get back a
    // `kv` struct containing the bytes and value as well as the actual
    // decoded keys:
    println!("Decoded key(s): {:?}", kv.keys);
    println!("Key bytes: 0x{}", hex::encode(&kv.key_bytes));
    println!("Value: {:?}", kv.value);
}

When using the static interface, keys come back as a tuple of values corresponding to the different hashers used in constructing the key. When using a dynamic interface, keys will be encoded/decoded from the type given so long as it implements subxt::storage::StorageKey, eg Vec<scale_value::Value>.

Extrinsic Params Refinement (#1439)

Prior to this PR, one could configure extrinsic signed extensions by providing some params like so:

// Configure the transaction parameters; we give a small tip and set the
// transaction to live for 32 blocks from the `latest_block` above:
let tx_params = Params::new()
    .tip(1_000)
    .mortal(latest_block.header(), 32)
    .build();

let hash = api.tx().sign_and_submit(&tx, &from, tx_params).await?;

If you want to customize the account nonce, you'd use a different call like create_signed_with_nonce instead.

One of the downsides of the above approach is that, if you don't provide any explicit params, transactions will be immortal by default (because the signed extensions didn't have the information to do any better).

Now, with the help of a RefineParams trait, transactions will default to being mortal and living for 32 blocks unless an explicit mortality is provided as above.

One notable change is that the offline-only create_signed_with_nonce and create_partial_signed_with_nonce functions have lost the _with_nonce suffix. Since we can't discover nonce/mortality settings offline, you should now provide Params and set an explicit nonce (and mortality, if you like) when using these calls, otherwise the nonce will be set to 0 and the mortality to Immortal.

For a full list of changes, please see the following:

Added

• Reworked light client (#1475)
• no_std compatibility for subxt-signer (#1477)
• Typed Storage Keys (#1419)
• Extrinsic Params Refinement (#1439)
• Make storage_page_size for the LegacyBackend configurable (#1458)
• no_std compatibility for subxt-metadata (#1401)
• Experimental reconnecting-rpc-client (#1396)

Changed

• scale-type-resolver integration (#1460)
• subxt: Derive std::cmp traits for subxt payloads and addresses (#1429)
• CLI: Return error on wrongly specified type paths (#1397)
• rpc v2: chainhead support multiple finalized block hashes in FollowEvent::Initialized (#1476)
• rpc v2: rename transaction to transactionWatch (#1399)

Fixed

• Avoid a panic in case we try decoding naff bytes (#1444)
• Fix error mapping to wrong transaction status (#1445)
• Update DispatchError to match latest in polkadot-sdk (#1442)
• Handle errors when fetching storage keys from Unstablebackend (#1440)
• Swap type aliases around to be semantically correct (#1441)

This release introduces a bunch of features that make subxt easier to use. Let's look at a few of them.

Codegen - Integrating scale-typegen and adding type aliases (#1249)

We rewrote the code generation functionality of subxt and outsourced it to the new scale-typegen crate, which serves a more general purpose.

Since a lot of types used in substrate are rich with generics, this release introduces type aliases into the generated code. A type alias is generated for the arguments/keys or each call, storage entry, and runtime API method (#1249).

Macro - Errors for misspecified type paths (#1339)

The subxt macro provides attributes to specify custom derives, attributes, and type substitutions on a per-type basis. Previously we did not verify that the provided type paths are part of the metadata. This is now fixed: If you provide an invalid type path, the macro will tell you so. It also suggests similar type paths, you might have meant instead.

#[subxt::subxt(
    runtime_metadata_path = "metadata.scale",
    derive_for_type(path = "Junctions", derive = "Clone")
)]
pub mod polkadot {}

This gives you a compile-time error like this:

Type `Junctions` does not exist at path `Junctions`

A type with the same name is present at:
xcm::v3::junctions::Junctions
xcm::v2::multilocation::Junctions

Macro - Recursive derives and attributes (#1379)

Previously adding derives on a type containing other types was also cumbersome, see this example:

#[subxt::subxt(
    runtime_metadata_path = "metadata.scale",
    derive_for_type(path = "xcm::v2::multilocation::MultiLocation", derive = "Clone"),
    derive_for_type(path = "xcm::v2::multilocation::Junctions", derive = "Clone"),
    derive_for_type(path = "xcm::v2::junction::Junction", derive = "Clone"),
    derive_for_type(path = "xcm::v2::NetworkId", derive = "Clone"),
    derive_for_type(path = "xcm::v2::BodyId", derive = "Clone"),
    derive_for_type(path = "xcm::v2::BodyPart", derive = "Clone"),
    derive_for_type(
        path = "bounded_collections::weak_bounded_vec::WeakBoundedVec",
        derive = "Clone"
    )
)]
pub mod polkadot {}

We introduced a recursive flag for custom derives and attributes that automatically inserts the specified derives on all child types:

#[subxt::subxt(
    runtime_metadata_path = "metadata.scale",
    derive_for_type(path = "xcm::v2::multilocation::MultiLocation", derive = "Clone", recursive),
)]
pub mod polkadot {}

Subxt CLI - New features and usability improvements (#1290, #1336, and #1379)

Our CLI tool now allows you to explore runtime APIs and events (#1290). We also fully integrated with scale-typegen-description, a crate that can describe types in a friendly way and provide type examples. The output is also color-coded to be easier on the eyes. Get started with these commands:

# Show details about a runtime API call:
subxt explore --url wss://westend-rpc.polkadot.io api StakingAPI nominations_quota
# Execute a runtime API call from the CLI:
subxt explore --url wss://westend-rpc.polkadot.io api core version -e
# Discover what events a pallet can emit:
subxt explore --url wss://westend-rpc.polkadot.io pallet Balances events

All CLI commands that take some metadata via --file or --url, can now also read the metadata directly from stdin with --file - (#1336). This allows you to pipe in metadata from other processes like in this command chain:

parachain-node export-metadata | subxt codegen --file - | rustfmt > main.rs

Similar to the macro, the subxt codegen command can now also use recursive flags:

subxt codegen --derive-for-type xcm::v2::multilocation::MultiLocation=Clone,recursive
subxt codegen --attributes-for-type "xcm::v2::multilocation::MultiLocation=#[myerror],recursive"

Minor changes and things to be aware of

• Using insecure connections is now an explicit opt-in in many places (#1309)
• When decoding extrinsics from a block into a static type, we now return it's details (e.g. signature, signed extensions, raw bytes) alongside the statically decoded extrinsic itself (#1376)

We also made a few fixes and improvements around the unstable backend and the lightclient, preparing them for more stable usage in the future.

Added

• Errors for misspecified type paths + suggestions (#1339)
• CLI: Recursive derives and attributes (#1379)
• CLI: Explore runtime APIs and events, colorized outputs, scale-typegen integration for examples (#1290)
• Add chainflip to real world usage section of README (#1351)
• CLI: Allow using --file - to read metadata from stdin (#1336)
• Codegen: Generate type aliases for better API ergonomics (#1249)

Changed

• Return Pending rather than loop around if no new finalized hash in submit_transaction (#1378)
• Return ExtrinsicDetails alongside decoded static extrinsics (#1376)
• Improve Signed Extension and Block Decoding Examples/Book (#1357)
• Use scale-typegen as a backend for the codegen (#1260)
• Using insecure connections is now opt-in (#1309)

Fixed

• Ensure lightclient chainSpec is at least one block old (#1372)
• Typo fix in docs (#1370)
• Don't unpin blocks that may show up again (#1368)
• Runtime upgrades in unstable backend (#1348)
• Generate docs for feature gated items (#1332)
• Backend: Remove only finalized blocks from the event window (#1356)
• Runtime updates: wait until upgrade on chain (#1321)
• Cache extrinsic events (#1327)

This release makes a bunch of small QoL improvements and changes. Let's look at the main ones.

Add support for configuring multiple chains (#1238)

The light client support previously provided a high level interface for connecting to single chains (ie relay chains). This PR exposes a "low level" interface which allows smoldot (the light client implementation we use) to be configured somewhat more arbitrarily, and then converted into a valid subxt OnlineClient to be used.

See this example for more on how to do this.

We'll likely refine this over time and add a slightly higher level interface to make common operations much easier to do.

Support decoding signed extensions (#1209 and #1235)

This PR makes it possible to decode the signed extensions in extrinsics. This looks something like:

let api = OnlineClient::<PolkadotConfig>::new().await?;

// Get blocks; here we just subscribe to them:
let mut blocks_sub = api.blocks().subscribe_finalized().await?;

while let Some(block) = blocks_sub.next().await {
    let block = block?;

    // Fetch the extrinsics in the block:
    let extrinsics = block.extrinsics().await?;

    // Iterate over them:
    for extrinsic in extrinsics.iter() {

        // Returns None if the extrinsic isn't signed, so no signed extensions:
        let Some(signed_exts) = extrinsic.signed_extensions() else {
            continue;
        };

        // We can ask for a couple of common values, None if not found:
        println!("Tip: {:?}", signed_exts.tip());
        println!("Nonce: {:?}", signed_exts.tip());

        // Or we can find and decode into a static signed extension type
        // (Err if we hit a decode error first, then None if it's not found):
        if let Ok(Some(era)) = signed_exts.find::<CheckMortality<PolkadotConfig>>() {
            println!("Era: {era:?}");
        }

        // Or we can iterate over the signed extensions to work with them:
        for signed_ext in signed_exts {
            println!("Signed Extension name: {}", signed_ext.name());

            // We can try to statically decode each one:
            if let Ok(Some(era)) = signed_ext.as_signed_extension::<CheckMortality<PolkadotConfig>>() {
                println!("Era: {era:?}");
            }

            // Or we can dynamically decode it into a `scale_value::Value`:
            if let Ok(value) = signed_ext.value() {
                println!("Decoded extension: {value}");
            }
        }
    }
}

See the API docs for more.

ChargeAssetTxPayment: Add support for generic AssetId

Still on the topic of signed extensions, the ChargeAssetTxPayment extension was previously not able to be used with a generic AssetId, which prohibited it from being used on the Asset Hub (which uses a MultiLocation instead). To address this, we added an AssetId type to our subxt::Config, which can now be configured.

One example of doing that can be found here.

This example uses a generated MultiLocation type to be used as the AssetId. Currently it requires a rather hideous set of manual clones like so:

#[subxt::subxt(
    runtime_metadata_path = "../artifacts/polkadot_metadata_full.scale",
    derive_for_type(path = "xcm::v2::multilocation::MultiLocation", derive = "Clone"),
    derive_for_type(path = "xcm::v2::multilocation::Junctions", derive = "Clone"),
    derive_for_type(path = "xcm::v2::junction::Junction", derive = "Clone"),
    derive_for_type(path = "xcm::v2::NetworkId", derive = "Clone"),
    derive_for_type(path = "xcm::v2::BodyId", derive = "Clone"),
    derive_for_type(path = "xcm::v2::BodyPart", derive = "Clone"),
    derive_for_type(
        path = "bounded_collections::weak_bounded_vec::WeakBoundedVec",
        derive = "Clone"
    )
)]

This is something we plan to address in the next version of Subxt.

Change SignedExtension matching logic (#1283)

Before this release, each signed extension had a unique name (SignedExtension::NAME). We'd use this name to figure out which signed extensions to apply for a given chain inside the signed_extensions::AnyOf type.

However, we recently ran into a new signed extension in Substrate called SkipCheckIfFeeless. This extension would wrap another signed extension, but maintained its own name. It has since been "hidden" from the public Substrate interface again, but a result of encountering this is that we have generalised the way that we "match" on signed extensions, so that we can be smarter about it going forwards.

So now, for a given signed extension, we go from:

impl<T: Config> SignedExtension<T> for ChargeAssetTxPayment<T> {
    const NAME: &'static str = "ChargeAssetTxPayment";
    type Decoded = Self;
}

To:

impl<T: Config> SignedExtension<T> for ChargeAssetTxPayment<T> {
    type Decoded = Self;
    fn matches(identifier: &str, type_id: u32, types: &PortableRegistry) -> bool {
        identifier == "ChargeAssetTxPayment"
    }
}

On the whole, we continue matching by name, as in the example above, but this allows an author to inspect the type of the signed extension (and subtypes of it) too if they want the signed extension to match (and thus be used) only in certain cases.

Remove wait_for_in_block helper method (#1237)

One can no longer use tx.wait_for_in_block to wait for a transaction to enter a block. The reason for this removal is that, especially when we migrate to the new chainHead APIs, we will no longer be able to reliably obtain any details about the block that the transaction made it into.

In other words, the following sort of thing would often fail:

tx.wait_for_in_block()
  .await?
  .wait_for_success()
  .await?;

The reason for this is that the block announced in the transaction status may not have been "pinned" yet in the new APIs. In the old APIs, errors would occasionally be encountered because the block announced may have been pruned by the time we ask for details for it. Overall; having an "unreliable" higher level API felt like a potential foot gun.

That said, you can still achieve the same via the lower level APIs like so:

while let Some(status) = tx.next().await {
    match status? {
        TxStatus::InBestBlock(tx_in_block) | TxStatus::InFinalizedBlock(tx_in_block) => {
            // now, we can attempt to work with the block, eg:
            tx_in_block.wait_for_success().await?;
        },
        TxStatus::Error { message } | TxStatus::Invalid { message } | TxStatus::Dropped { message } => {
            // Handle any errors:
            println!("Error submitting tx: {message}");
        },
        // Continue otherwise:
        _ => continue,
    }
}

Subxt-codegen: Tidy crate interface (#1225)

The subxt-codegen crate has always been a bit of a mess because it wasn't really supposed to be used outside of the subxt crates, which had led to issues like https://github.com/paritytech/subxt/issues/1211.

This PR tidies up the interface to that crate so that it's much easier now to programmatically generate the Subxt interface. Now, we have three properly supported ways to do this, depending on your needs:

1. Using the #[subxt] macro.
2. Using the subxt codegen CLI command.
3. Programmatically via the subxt-codegen crate.

Each method aims to expose a similar and consistent set of options.

If you were previously looking to use parts of the type generation logic to, for instance, generate runtime types but not the rest of the Subxt interface, then the https://github.com/paritytech/scale-typegen crate will aim to fill this role eventually.

That sums up the most significant changes. A summary of all of the relevant changes is as follows:

Added

• CLI: Add command to fetch chainSpec and optimize its size (#1278)
• Add legacy RPC usage example (#1279)
• impl RpcClientT for Arc<T> and Box<T> (#1277)
• RPC: Implement legacy RPC system_account_next_index (#1250)
• Lightclient: Add support for configuring multiple chains (#1238)
• Extrinsics: Allow static decoding of signed extensions (#1235)
• Extrinsics: Support decoding signed extensions (#1209)
• ChargeAssetTxPayment: Add support for generic AssetId (eg u32 or MultiLocation) (#1227)
• Add Clone + Debug on Payloads/Addresses, and compare child storage results (#1203)

Changed

• Lightclient: Update smoldot to 0.14.0 and smoldot-light to 0.12.0 (#1307)
• Cargo: Switch to workspace lints (#1299)
• Update substrate-* and signer-related dependencies (#1297)
• Change SignedExtension matching logic and remove SkipCheckIfFeeless bits (#1283)
• Update the README with the new location of node-cli (#1282)
• Generalize substrate-compat impls to accept any valid hasher/header impl (#1265)
• Extrinsics: Remove wait_for_in_block helper method (#1237)
• Subxt-codegen: Tidy crate interface (#1225)
• Lightclient: Update usage docs (#1223)
• Wee tidy to subxt-signer flags (#1200)
• Batch fetching storage values again to improve performance (#1199)
• Add subxt feature in subxt-signer crate to default features (#1193)

Fixed

• Trimmed metadata hash comparison fails in is_codegen_valid_for (#1306)
• Sync tx submission with chainHead_follow (#1305)
• Storage: Fix partial key storage iteration (#1298)
• Lightclient: Fix wasm socket closure called after being dropped (#1289)
• Fix parachain example (#1228)

This is a patch release, mainly to deploy the fix #1191, which resolves an issue around codegen when runtime API definitions have an argument name "_".

We also expose an API, api.blocks().at(block_hash).account_nonce(account_id), which allows one to obtain the account nonce for some account at any block hash, and not just at the latest finalized block hash as is possible via api.tx().account_nonce(..).

The main changes are:

• fix for when runtime API field name is _ (#1191)
• allow getting account nonce at arbitrary blocks, too (#1182)
• chore: improve some error messages (#1183)

This is a big release that adds quite a lot, and also introduces some slightly larger breaking changes. Let's look at the main changes:

The Backend trait and the UnstableBackend and LegacyBackend impls.

See #1126, #1137 and #1161 for more information.

The overarching idea here is that we want Subxt to be able to continue to support talking to nodes/light-clients using the "legacy" RPC APIs that are currently available, but we also want to be able to support using only the new RPC APIs once they are stabilized.

Until now, the higher level APIs in Subxt all had access to the RPCs and could call whatever they needed. Now, we've abstracted away which RPCs are called (or even that RPCs are used at all) behind a subxt::backend::Backend trait. Higher level APIs no longer have access to RPC methods and instead have access to the current Backend implementation. We then added two Backend implementations:

• subxt::backend::legacy::LegacyBackend: This uses the "legacy" RPCs, as we've done to date, to obtain the information we need. This is still the default backend that Subxt will use.
• subxt::backend::unstable::UnstableBackend: This backend relies on the new (and currently still unstable) chainHead based RPC APIs to obtain the information we need. This could break at any time as the RPC methods update, until they are fully stabilized. One day, this will be the default backend.

One of the significant differences between backends is that the UnstableBackend can only fetch further information about blocks that are "pinned", ie that we have signalled are still in use. To that end, the backend now hands back BlockRefs instead of plain block hashes. As long as a BlockRef exists for some block, the backend (and node) will attempt to keep it available. Thus, Subxt will keep hold of these internally as needed, and also allows you to obtain them from a Block with block.reference(), in case you need to try and hold on to any blocks for longer.

One of the main breaking changes here is in how you can access and call RPC methods.

Previously, you could access them directly from the Subxt client, since it exposed the RPC methods itself, eg:

let genesis_hash = client.rpc().genesis_hash().await?;

Now, the client only knows about a Backend (ie it has a .backend() method instead of .rpc()), and doesn't know about RPCs, but you can still manually create an RpcClient to call RPC methods like so:

use subxt::{
    config::SubstrateConfig,
    backend::rpc::RpcClient,
    backend::legacy::LegacyRpcMethods,
};

// Instantiate an RPC client pointing at some URL.
let rpc_client = RpcClient::from_url("ws://localhost:9944").await?;

// We could also call unstable RPCs with `backend::unstable::UnstableRpcMethods`:
let rpc_methods = LegacyRpcMethods::<SubstrateConfig>::new(rpc_client);

// Use it to make RPC calls, here calling the legacy genesis_hash method.
let genesis_hash = rpc_methods.genesis_hash().await?

If you'd like to share a single client for RPCs and Subxt usage, you can clone this RPC client and run OnlineClient::<SubstrateConfig>::from_rpc_client(rpc_client) to create a Subxt client using it.

Another side effect of this change is that RPC related things have moved from subxt::rpc::* to subxt::backend::rpc::* and some renaming has happened along the way.

A number of smaller breaking changes have also been made in order to expose details that are compatible with both sets of RPCs, and to generally move Subxt towards working well with the new APIs and exposing things in a consistent way:

• The storage methods fetch_keys is renamed to fetch_raw_keys (this just for consistency with fetch_raw).
• The storage method iter no longer accepts a page_size argument, and each item returned is now an Option<Result<(key, val)>> instead of a Result<Option<(key, val)>> (we now return a valid Stream implementation for storage entry iteration). See this example.
• The events returned when you manually watch a transaction have changed in order to be consistent with the new RPC APIs (the new events can be seen here), and next_item => next. If you rely on higher level calls like sign_and_submit_then_watch, nothing has changed.
• Previously, using .at_latest() in various places would mean that calls would run against the latest best block. Now, all such calls will run against the latest finalized block. The latest best block is subject to changing or being pruned entirely, and can differ between nodes.
• .at(block_hash) should continue to work as-is, but can now also accept a BlockRef, to keep the relevant block around while you're using the associated APIs.
• To fetch the extrinsics in a block, you used to call block.body().await?.extrinsics(). This has now been simplified to block.extrinsics().await?.

Making ExtrinsicParams more flexible with SignedExtensions.

See #1107 for more information.

When configuring Subxt to work against a given chain, you needed to configure the ExtrinsicParams associated type to encode exactly what was required by the chain when submitting transactions. This could be difficult to get right.

Now, we have "upgraded" the ExtrinsicParams trait to give it access to metadata, so that it can be smarter about how to encode the correct values. We've also added a subxt::config::SignedExtension trait, and provided implementations of it for all of the "standard" signed extensions (though we have a little work to do still).

How can you use SignedExtensions? Well, subxt::config::signed_extensions::AnyOf<T, Params> is a type which can accept any tuple of SignedExtensions, and itself implements ExtrinsicParams. It's smart, and will use the metadata to know which of the signed extensions that you provided to actually use on a given chain. So, AnyOf makes it easy to compose whichever SignedExtensions you need to work with a chain.

Finally, we expose subxt::config::{ DefaultExtrinsicParams, DefaultExtrinsicParamsBuilder }; the former just uses AnyOf to automatically use any of the "standard" signed extensions as needed, and the latter provided a nice builder interface to configure any parameters for them. This is now the default type used in SubstrateConfig and PolkadotConfig, so long story short: those configurations (and particularly their ExtrinsicParams) are more likely to Just Work now across default chains.

See this example for how to create and use custom signed extensions, or this example for how to implement custom ExtrinsicParams if you'd prefer to ignore SignedExtensions entirely.

As a result of using the new DefaultExtrinsicParams in SubstrateConfig and PolkadotConfig, the interface to configure transactions has changed (and in fact been generally simplified). Configuring a mortal transaction with a small tip ƒor instance used to look like:

use subxt::config::polkadot::{Era, PlainTip, PolkadotExtrinsicParamsBuilder as Params};

let tx_params = Params::new()
    .tip(PlainTip::new(1_000))
    .era(Era::mortal(32, latest_block.header().number()), latest_block.header().hash());

let hash = api.tx().sign_and_submit(&tx, &from, tx_params).await?;

And now it will look like this:

use subxt::config::polkadot::PolkadotExtrinsicParamsBuilder as Params;

let tx_params = Params::new()
    .tip(1_000)
    .mortal(latest_block.header(), 32)
    .build();

let hash = api.tx().sign_and_submit(&tx, &from, tx_params).await?;

Check the docs for PolkadotExtrinsicParamsBuilder and the ExtrinsicParams trait for more information.

Storage: Allow iterating storage entries at different depths

See (#1079) for more information.

Previously, we could statically iterate over the root of some storage map using something like:

// Build a storage query to iterate over account information.
let storage_query = polkadot::storage().system().account_root();

// Get back an iterator of results (here, we are fetching 10 items at
// a time from the node, but we always iterate over one at a time).
let mut results = api.storage().at_latest().await?.iter(storage_query, 10).await?;

Now, the suffix _root has been renamed to _iter, and if the storage entry is for instance a double map (or greater depth), we'll also now generate _iter2, iter3 and so on, each accepting the keys needed to access the map at that depth to iterate the remainder. The above example now becomes:

// Build a storage query to iterate over account information.
let storage_query = polkadot::storage().system().account_iter();

// Get back an iterator of results
let mut results = api.storage().at_latest().await?.iter(storage_query).await?;

Note also that the pagination size no longer needs to be provided; that's handled internally by the relevant Backend.

Custom values

This is not a breaking change, but just a noteworthy addition; see #1106, #1117 and #1147 for more information.

V15 metadata allows chains to insert arbitrary information into a new "custom values" hashmap (see this). Subxt has now added APIs to allow accessing these custom values a little like how constants can be accessed.

Dynamically accessing custom values looks a bit like this:

// Obtain the raw bytes for some entry:
let custom_value_bytes: Vec<u8> = client.custom_values().bytes_at("custom-value-name")?;

// Obtain a representation of the value that we can attempt to decode:
let custom_value = client.custom_values().at("custom-value-name")?;

// Decode it into a runtime Value if possible:
let value: Value = custom_value.to_value()?;
// Or attempt to decode it into a specific type:
let value: Foo = custom_value.as_type()?;

We can also use codegen to statically access values, which makes use of validation and returns a known type whenever possible, for the added compile time safety this brings:

#[subxt::subxt(runtime_metadata_path = "metadata.scale")]
pub mod runtime {}

// The generated interface also exposes any custom values with known types and sensible names:
let value_addr = runtime::custom().custom_value_name();

// We can use this address to access and decode the relevant value from metadata:
let static_value = client.custom_values().at(&value_addr)?;
// Or just ask for the bytes for it:
let static_value_bytes = client.custom_values().bytes_at(&value_addr)?;

That sums up the most significant changes. All of the key commits in this release can be found here:

Added

• UnstableBackend: Add a chainHead based backend implementation (#1161)
• UnstableBackend: Expose the chainHead RPCs (#1137)
• Introduce Backend trait to allow different RPC (or other) backends to be implemented (#1126)
• Custom Values: Fixes and tests for "custom values" (#1147)
• Custom Values: Add generated APIs to statically access custom values in metadata (#1117)
• Custom Values: Support dynamically accessing custom values in metadata (#1106)
• Add storage_version() and runtime_wasm_code() to storage (#1111)
• Make ExtrinsicParams more flexible, and introduce signed extensions (#1107)

Changed

• subxt-codegen: Add "web" feature for WASM compilation that works with jsonrpsee (#1175)
• subxt-codegen: support compiling to WASM (#1154)
• CI: Use composite action to avoid dupe use-substrate code (#1177)
• Add custom Debug impl for DispatchError to avoid huge metadata output (#1153)
• Remove unused start_key that new RPC API may not be able to support (#1148)
• refactor(rpc): Use the default port if one isn't provided (#1122)
• Storage: Support iterating over NMaps with partial keys (#1079)

Fixed

• metadata: Generate runtime outer enums if not present in V14 (#1174)
• Remove "std" feature from sp-arithmetic to help substrate compat. (#1155)
• integration-tests: Increase the number of events we'll wait for (#1152)
• allow 'latest' metadata to be returned from the fallback code (#1127)
• chainHead: Propagate results on the chainHead_follow (#1116)

This is a small release whose primary goal is to bump the versions of scale-encode, scale-decode and scale-value being used, to benefit from recent changes in those crates.

scale-decode changes how compact values are decoded as part of #1103. A compact encoded struct should now be properly decoded into a struct of matching shape (which implements DecodeAsType). This will hopefully resolve issues around structs like Perbill. When decoding the SCALE bytes for such types into scale_value::Value, the Value will now be a composite type wrapping a value, and not just the value.

We've also figured out how to sign extrinsics using browser wallets when a Subxt app is compiled to WASM; see #1067 for more on that!

The key commits:

Added

• Add browser extension signing example (#1067)

Changed

• Bump to latest scale-encode/decode/value and fix test running (#1103)
• Set minimum supported rust-version to 1.70 (#1097)

Fixed

• Tests: support 'substrate-node' too and allow multiple binary paths (#1102)

This patch release fixes a small issue whereby using runtime_metadata_url in the Subxt macro would still attempt to download unstable metadata, which can fail at the moment if the chain has not updated to stable V15 metadata yet (which has a couple of changes from the last unstable version). Note that you're generally encouraged to use runtime_metadata_path instead, which does not have this issue.

Fixes

• codegen: Fetch and decode metadata version then fallback (#1092)

This release beings with it a number of exciting additions. Let's cover a few of the most significant ones:

Light client support (unstable)

This release adds support for light clients using Smoldot, both when compiling native binaries and when compiling to WASM to run in a browser environment. This is unstable for now while we continue testing it and work on making use of the new RPC APIs.

Here's how to use it:

use subxt::{
    client::{LightClient, LightClientBuilder},
    PolkadotConfig
};
use subxt_signer::sr25519::dev;

// Create a light client:
let api = LightClient::<PolkadotConfig>::builder()
    // You can also pass a chain spec directly using `build`, which is preferred:
    .build_from_url("ws://127.0.0.1:9944")
    .await?;

// Working with the interface is then the same as before:
let dest = dev::bob().public_key().into();
let balance_transfer_tx = polkadot::tx().balances().transfer(dest, 10_000);
let events = api
    .tx()
    .sign_and_submit_then_watch_default(&balance_transfer_tx, &dev::alice())
    .await?
    .wait_for_finalized_success()
    .await?;

At the moment you may encounter certain things that don't work; please file an issue if you do!

V15 Metadata

This release stabilizes the metadata V15 interface, which brings a few changes but primarily allows you to interact with Runtime APIs via an ergonomic Subxt interface:

// We can use the static interface to interact in a type safe way:
#[subxt::subxt(runtime_metadata_path = "path/to/metadata.scale")]
pub mod polkadot {}

let runtime_call = polkadot::apis()
    .metadata()
    .metadata_versions();

// Or we can use the dynamic interface like so:
use subxt::dynamic::Value;

let runtime_call = subxt::dynamic::runtime_api_call(
    "Metadata",
    "metadata_versions",
    Vec::<Value<()>>::new()
);

This is no longer behind a feature flag, but if the chain you're connecting to doesn't use V15 metadata yet then the above will be unavailable.

subxt-signer

The new subxt-signer crate provides the ability to sign transactions using either sr25519 or ECDSA. It's WASM compatible, and brings in fewer dependencies than using sp_core/sp_keyring does, while having an easy to use interface. Here's an example of signing a transaction using it:

use subxt::{OnlineClient, PolkadotConfig};
use subxt_signer::sr25519::dev;

let api = OnlineClient::<PolkadotConfig>::new().await?;

// Build the extrinsic; a transfer to bob:
let dest = dev::bob().public_key().into();
let balance_transfer_tx = polkadot::tx().balances().transfer(dest, 10_000);

// Sign and submit the balance transfer extrinsic from Alice:
let from = dev::alice();
let events = api
    .tx()
    .sign_and_submit_then_watch_default(&balance_transfer_tx, &from)
    .await?
    .wait_for_finalized_success()
    .await?;

Dev keys should only be used for tests since they are publicly known. Actual keys can be generated from URIs, phrases or raw entropy, and derived using soft/hard junctions:

use subxt_signer::{ SecretUri, sr25519::Keypair };
use std::str::FromStr;

// From a phrase (see `bip39` crate on generating phrases):
let phrase = bip39::Mnemonic::parse(phrase).unwrap();
let keypair = Keypair::from_phrase(&phrase, Some("Password")).unwrap();

// Or from a URI:
let uri = SecretUri::from_str("//Alice").unwrap();
let keypair = Keypair::from_uri(&uri).unwrap();

// Deriving a new key from an existing one:
let keypair = keypair.derive([
    DeriveJunction::hard("Alice"),
    DeriveJunction::soft("stash")
]);

Breaking changes

A few small breaking changes have occurred:

• There is no longer a need for an Index associated type in your Config implementations; we now work it out dynamically where needed.
• The "substrate-compat" feature flag is no longer enabled by default. subxt-signer added native signing support and can be used instead of bringing in Substrate dependencies to sign transactions now. You can still enable this feature flag as before to make use of them if needed.
  • Note: Be aware that Substrate crates haven't been published in a while and have fallen out of date, though. This will be addressed eventually, and when it is we can bring the Substrate crates back uptodate here.

For anything else that crops up, the compile errors and API docs will hopefully point you in the right direction, but please raise an issue if not.

For a full list of changes, see below:

Added

• Example: How to connect to parachain (#1043)
• ECDSA Support in signer (#1064)
• Add subxt_signer crate for native & WASM compatible signing (#1016)
• Add light client platform WASM compatible (#1026)
• light-client: Add experimental light-client support (#965)
• Add diff command to CLI tool to visualize metadata changes (#1015)
• CLI: Allow output to be written to file (#1018)

Changed

• Remove substrate-compat default feature flag (#1078)
• runtime API: Substitute UncheckedExtrinsic with custom encoding (#1076)
• Remove Index type from Config trait (#1074)
• Utilize Metadata V15 (#1041)
• chain_getBlock extrinsics encoding (#1024)
• Make tx payload details public (#1014)
• CLI tool tests (#977)
• Support NonZero numbers (#1012)
• Get account nonce via state_call (#1002)
• add #[allow(rustdoc::broken_intra_doc_links)] to subxt-codegen (#998)

Fixed

• remove parens in hex output for CLI tool (#1017)
• Prevent bugs when reusing type ids in hashing (#1075)
• Fix invalid generation of types with >1 generic parameters (#1023)
• Fix jsonrpsee web features (#1025)
• Fix codegen validation when Runtime APIs are stripped (#1000)
• Fix hyperlink (#994)
• Remove invalid redundant clone warning (#996)

This is another big release for Subxt with a bunch of awesome changes. Let's talk about some of the notable ones:

A new guide

This release will come with overhauled documentation and examples which is much more comprehensive than before, and goes into much more detail on each of the main areas that Subxt can work in.

Check out the documentation for more. We'll continue to build on this with some larger examples, too, going forwards. (#968) is particularly cool as it's our first example showcasing Subxt working with Yew and WASM; it'll be extended with more documentation and things in the next release.

A more powerful CLI tool: an explore command.

The CLI tool has grown a new command, explore. Point it at a node and use explore to get information about the calls, constants and storage of a node, with a helpful interface that allows you to progressively dig into each of these areas!

Support for (unstable) V15 metadata and generating a Runtime API interface

One of the biggest changes in this version is that, given (unstable) V15 metadata, Subxt can now generate a nice interface to make working with Runtime APIs as easy as building extrinsics or storage queries. This is currently unstable until the V15 metadata format is stabilised, and so will break as we introduce more tweaks to the metadata format. We hope to stabilise V15 metadata soon; see this for more information. At this point, we'll stabilize support in Subxt.

Support for decoding extrinsics

Up until now, you were able to retrieve the bytes for extrinsics, but weren't able to use Subxt to do much with those bytes.

Now, we expose several methods to decode extrinsics that work much like decoding events:

#[subxt::subxt(runtime_metadata_path = "polkadot_metadata.scale")]
pub mod polkadot {}

// Get some block:
let block = api.blocks().at_latest().await?;

// Find and decode a specific extrinsic in the block:
let remark = block.find::<polkadot::system::calls::Remark>()?;

// Iterate the extrinsics in the block:
for ext in block.iter() {
    // Decode a specific extrinsic into the call data:
    let remark = ext.as_extrinsic::<polkadot::system::calls::Remark>()?;
    // Decode any extrinsic into an enum containing the call data:
    let extrinsic = ext.as_root_extrinsic::<polkadot::Call>()?;
}

New Metadata Type (#974)

Previously, the subxt_metadata crate was simply a collection of functions that worked directly on frame_metadata types. Then, in subxt, we had a custom metadata type which wrapped this to provide the interface needed by various Subxt internals and traits.

Now, the subxt_metadata crate exposes our own Metadata type which can be decoded from the same wire format as the frame_metadata types we used to use. This type is now used throughout Subxt, as well as in the codegen stuff, and provides a single unified interface for working with metadata that is independent of the actual underlying metadata version we're using.

This shouldn't lead to breakages in most code, but if you need to load metadata for an OfflineClient you might previously have done this:

use subxt::ext::frame_metadata::RuntimeMetadataPrefixed;
use subxt::metadata::Metadata;

let metadata = RuntimeMetadataPrefixed::decode(&mut &*bytes).unwrap();
let metadata = Metadata::try_from(metadata).unwrap();

But now you'd do this:

use subxt::metadata::Metadata;

let metadata = Metadata::decode(&mut &*bytes).unwrap();

Otherwise, if you implement traits like TxPayload directly, you'll need to tweak the implementations to use the new Metadata type, which exposes everything you used to be able to get hold of but behind a slightly different interface.

Removing as_pallet_event method (#953)

In an effort to simplify the number of ways we have to decode events, as_pallet_event was removed. You can achieve a similar thing by calling as_root_event, which will decode any event that the static interface knows about into an outer enum of pallet names to event names. if you only care about a specific event, you can match on this enum to look for events from a specific pallet.

Another reason that as_pallet_event was removed was that it could potentially decode events from the wrong pallets into what you're looking for, if the event shapes happened to line up, which was a potential foot gun.

Added as_root_error for decoding errors.

Much like we can call as_root_extrinsic or as_root_event to decode extrinsics and events into a top level enum, we've also added as_root_error to do the same for errors and help to make this interface consistent across the board.

Beyond these, there's a bunch more that's been added, fixed and changes. A full list of the notable changes in this release are as follows:

Added

• Add topics to EventDetails (#989)
• Yew Subxt WASM examples (#968)
• CLI subxt explore commands (#950)
• Retain specific runtime APIs (#961)
• Subxt Guide (#890)
• Partial fee estimates for SubmittableExtrinsic (#910)
• Add ability to opt out from default derives and attributes (#925)
• add no_default_substitutions to the macro and cli (#936)
• extrinsics: Decode extrinsics from blocks (#929)
• Metadata V15: Generate Runtime APIs (#918) and (#947)
• impl Header and Hasher for some substrate types behind the "substrate-compat" feature flag (#934)
• add as_root_error for helping to decode ModuleErrors (#930)

Changed

• Update scale-encode, scale-decode and scale-value to latest (#991)
• restrict sign_with_address_and_signature interface (#988)
• Introduce Metadata type (#974) and (#978)
• Have a pass over metadata validation (#959)
• remove as_pallet_extrinsic and as_pallet_event (#953)
• speed up ui tests. (#944)
• cli: Use WS by default instead of HTTP (#954)
• Upgrade to syn 2.0 (#875)
• Move all deps to workspace toml (#932)
• Speed up CI (#928) and (#926)
• metadata: Use v15 internally (#912)
• Factor substrate node runner into separate crate (#913)
• Remove need to import parity-scale-codec to use subxt macro (#907)

Fixed

• use blake2 for extrinsic hashing (#921)
• Ensure unique types in codegen (#967)
• use unit type in polkadot config (#943)

This is a fairly significant change; what follows is a description of the main changes to be aware of:

Unify how we encode and decode static and dynamic types (#842)

Prior to this, static types generated by codegen (ie subxt macro) would implement Encode and Decode from the parity-scale-codec library. This meant that they woule be encoded-to and decoded-from based on their shape. Dynamic types (eg the subxt::dynamic::Value type) would be encoded and decoded based on the node metadata instead.

This change makes use of the new scale-encode and scale-decode crates to auto-implement EncodeAsType and DecodeAsType on all of our static types. These traits allow types to take the node metadata into account when working out how best to encode and decode into them. By using metadata, we can be much more flexible/robust about how to encode/decode various types (as an example, nested transactions will now be portable across runtimes). Additionally, we can merge our codepaths for static and dynamic encoding/decoding, since both static and dynamic types can implement these traits. Read the PR description for more info.

A notable impact of this is that any types you wish to substitute when performing codegen (via the CLI tool or #[subxt] macro) must also implement EncodeAsType and DecodeAsType too. Substrate types, for instance, generally do not. To work around this, #886 introduces a Static type and enhances the type substitution logic so that you're able to wrap any types which only implement Encode and Decode to work (note that you lose out on the improvements from EncodeAsType and DecodeAsType when you do this):

#[subxt::subxt(
    runtime_metadata_path = "/path/to/metadata.scale",
    substitute_type(
        type = "sp_runtime::multiaddress::MultiAddress<A, B>",
        with = "::subxt::utils::Static<::sp_runtime::multiaddress::MultiAddress<A, B>>"
    )
)]
pub mod node_runtime {}

So, if you want to substitute in Substrate types, wrap them in ::subxt::utils::Static in the type substitution, as above. #886 also generally improves type substitution so that you can substitute the generic params in nested types, since it's required in the above.

Several types have been renamed as a result of this unification (though they aren't commonly made explicit use of). Additionally, to obtain the bytes from a storage address, instead of doing:

let addr_bytes = storage_address.to_bytes()

You must now do:

let addr_bytes = cxt.client().storage().address_bytes(&storage_address).unwrap();

This is because the address on it's own no longer requires as much static information, and relies more heavily now on the node metadata to encode it to bytes.

Expose Signer payload (#861)

This is not a breaking change, but notable in that is adds create_partial_signed_with_nonce and create_partial_signed to the TxClient to allow you to break extrinsic creation into two steps:

1. building a payload, and then
2. when a signature is provided, getting back an extrinsic ready to be submitted.

This allows a signer payload to be obtained from Subxt, handed off to some external application, and then once a signature has been obtained, that can be passed back to Subxt to complete the creation of an extrinsic. This opens the door to using browser wallet extensions, for instance, to sign Subxt payloads.

Stripping unneeded pallets from metadata (#879)

This is not a breaking change, but adds the ability to use the Subxt CLI tool to strip out all but some named list of pallets from a metadata bundle. Aside from allowing you to store a significantly smaller metadata bundle with only the APIs you need in it, it will also lead to faster codegen, since there's much less of it to do.

Use a command like subxt metadata --pallets Balances,System to select specific pallets. You can provide an existing metadata file to take that and strip it, outputting a smaller bundle. Alternately it will grab the metadata from a local node and strip that before outputting.

Dispatch error changes (#878)

The DispatchError returned from either attempting to submit an extrinsic, or from calling .dry_run() has changed. It's now far more complete with respect to the information it returns in each case, and the interface has been tidied up. Changes include:

• For ModuleError's, instead of err.pallet and err.error, you can obtain error details using let details = err.details()? and then details.pallet() and details.error().
• DryRunResult is now a custom enum with 3 states, Success, DispatchError or TransactionValidityError. The middle of these contains much more information than previously.
• Errors in general have been marked #[non_exahustive] since they could grow and change at any time. (Owing to our use of scale-decode internally, we are not so contrained when it comes to having precise variant indexes or anything now, and can potentially deprecate rather than remove old variants as needed).
• On a lower level, the rpc.dry_run() RPC call now returns the raw dry run bytes which can then be decoded with the help of metadata into our DryRunResult.

Extrinsic submission changes (#897)

It was found by @furoxr that Substrate nodes will stop sending transaction progress events under more circumstances than we originally expected. Thus, now calls like wait_for_finalized() and wait_for_in_block() will stop waiting for events when any of the following is sent from the node:

• Usurped
• Finalized
• FinalityTimeout
• Invalid
• Dropped

Previously we'd only close the subscription and stop waiting when we saw a Finalized or FinalityTimeout event. Thanks for digging into this @furoxr!

Add at_latest() method (#900 and #904)

A small breaking change; previously we had .at(None) or .at(Some(block_hash)) methods in a few places to obtain things at either the latest block or some specific block hash.

This API has been clarified; we now have .at_latest() to obtain the thing at the latest block, or .at(block_hash) (note; no more option) to obtain the thing at some fixed block hash. In a few instances this has allowed us to ditch the async from the .at() call.

That covers the larger changes in this release. For more details, have a look at all of the notable PRs since the last release here:

Added

• added at_latest (#900 and #904)
• Metadata: Retain a subset of metadata pallets (#879)
• Expose signer payload to allow external signing (#861)
• Add ink! as a user of subxt (#837)
• codegen: Add codegen error (#841)
• codegen: allow documentation to be opted out of (#843)
• re-export sp_core and sp_runtime (#853)
• Allow generating only runtime types in subxt macro (#845)
• Add 'Static' type and improve type substitution codegen to accept it (#886)

Changed

• Improve Dispatch Errors (#878)
• Use scale-encode and scale-decode to encode and decode based on metadata (#842)
• For smoldot: support deserializing block number in header from hex or number (#863)
• Bump Substrate dependencies to latest (#905)

Fixed

• wait_for_finalized behavior if the tx dropped, usurped or invalid (#897)

Added

• Add find_last for block types (#825)

This is a fairly small release, primarily to bump substrate dependencies to their latest versions.

The main breaking change is fairly small: #804. Here, the BlockNumber associated type has been removed from Config entirely, since it wasn't actually needed anywhere in Subxt. Additionally, the constraints on each of those associated types in Config were made more precise, primarily to tidy things up (but this should result in types more easily being able to meet the requirements here). If you use custom Config, the fix is simply to remove the BlockNumber type. If you also use the Config trait in your own functions and depend on those constraints, you may be able to define a custom MyConfig type which builds off Config and adds back any additional bounds that you want.

Note worthy PRs merged since the last release:

Added

• Add find last function (#821)
• Doc: first item is current version comment (#817)

Changed

• Remove unneeded Config bounds and BlockNumber associated type (#804)

This release adds a number of improvements, most notably:

• We make Substrate dependencies optional (#760), which makes WASM builds both smaller and more reliable. To do this, we re-implement some core types like AccountId32, MultiAddress and MultiSignature internally.
• Allow access to storage entries (#774) and runtime API's (#777) from some block. This is part of a move towards a more "block centric" interface, which will better align with the newly available chainHead style RPC interface.
• Add RPC methods for the new chainHead style interface (see https://paritytech.github.io/json-rpc-interface-spec/). These are currently unstable, but will allow users to start experimenting with this new API if their nodes support it.
• More advanced type substitution is now possible in the codegen interface (#735).

This release introduces a number of breaking changes that can be generally be fixed with mechanical tweaks to your code. The notable changes are described below.

Make Storage API more Block-centric

See #774. This PR makes the Storage API more consistent with the Events API, and allows access to it from a given block as part of a push to provide a more block centric API that will hopefully be easier to understand, and will align with the new RPC chainHead style RPC interface.

Before, your code will look like:

let a = api.storage().fetch(&staking_bonded, None).await?;

After, it should look like:

let a = api.storage().at(None).await?.fetch(&staking_bonded).await?;

Essentially, the final parameter for choosing which block to call some method at has been moved out of the storage method itself and is now provided to instantiate the storage API, either explicitly via an .at(optional_block_hash) as above, or implicitly when calling block.storage() to access the same storage methods for some block.

An alternate way to access the same storage (primarily used if you have subscribed to blocks or otherwise are working with some block) now is:

let block = api.blocks().at(None).await?
let a = block.storage().fetch(&staking_bonded, None).await?;

More advanced type substitution in codegen

See #735. Previously, you could perform basic type substitution like this:

#[subxt::subxt(runtime_metadata_path = "../polkadot_metadata.scale")]
pub mod node_runtime {
    #[subxt::subxt(substitute_type = "sp_arithmetic::per_things::Foo")]
    use crate::Foo;
}

This example would use crate::Foo every time an sp_arithmetic::per_things::Foo was encountered in the codegen. However, this was limited; the substitute type had to have the name number and order of generic parameters for this to work.

We've changed the interface above into:

#[subxt::subxt(
    runtime_metadata_path = "../polkadot_metadata.scale",
    substitute_type(
        type = "sp_arithmetic::per_things::Foo<A, B, C>",
        with = "crate::Foo<C>"
    )
)]
pub mod node_runtime {}

In this example, we can (optionally) specify the generic parameters we expect to see on the original type ("type"), and then of those, decide which should be present on the substitute type ("with"). If no parameters are provided at all, we'll get the same behaviour as before. This allows much more flexibility when defining substitute types.

Optional Substrate dependencies

See #760. Subxt now has a "substrate-compat" feature (enabled by default, and disabled for WASM builds). At present, enabling this feature simply exposes the PairSigner (which was always available before), allowing transactions to be signed via Substrate signer logic (as before). When disabled, you (currently) must bring your own signer implementation, but in return we can avoid bringing in a substantial number of Substrate dependencies in the process.

Regardless, this change also tidied up and moved various bits and pieces around to be consistent with this goal. To address some common moves, previously we'd have:

use subxt::{
    ext::{
        sp_core::{ sr25519, Pair },
        sp_runtime::{ AccountId32, generic::Header },
    },
    tx::{
        Era,
        PlainTip,
        PolkadotExtrinsicParamsBuilder
    }
};

And now this would look more like:

// `sp_core` and `sp_runtime` are no longer exposed via `ext`; add the crates yourself at matching versions to use:
use sp_core::{
    sr25519,
    Pair,
};
use subxt::{
    // You'll often want to use the "built-in" `AccountId32` now instead of the `sp_runtime` version:
    utils::AccountId32,
    // traits used in our `Config` trait are now provided directly in this module:
    config::Header,
    // Polkadot and Substrate specific Config types are now in the relevant Config section:
    config::polkadot::{
        Era,
        PlainTip,
        PolkadotExtrinsicParamsBuilder
    }
}

Additionally, the type Hashing in the Config trait is now called Hasher, to clarify what it is, and types returned directly from the RPC calls now all live in crate::rpc::types, rather than sometimes living in Substrate crates.

Some other note worthy PRs that were merged since the last release:

Added

• Add block-centric Storage API (#774)
• Add chainHead RPC methods (#766)
• Allow for remapping type parameters in type substitutions (#735)
• Add ability to set custom metadata etc on OnlineClient (#794)
• Add Cargo.lock for deterministic builds (#795)
• Add API to execute runtime calls (#777)
• Add bitvec-like generic support to the scale-bits type for use in codegen (#718)
• Add --derive-for-type to cli (#708)

Changed

• rename subscribe_to_updates() to updater() (#792)
• Expose Update (#791)
• Expose version info in CLI tool with build-time obtained git hash (#787)
• Implement deserialize on AccountId32 (#773)
• Codegen: Preserve attrs and add #[allow(clippy::all)] (#784)
• make ChainBlockExtrinsic cloneable (#778)
• Make sp_core and sp_runtime dependencies optional, and bump to latest (#760)
• Make verbose rpc error display (#758)
• rpc: Expose the subscription ID for RpcClientT (#733)
• events: Fetch metadata at arbitrary blocks (#727)

Fixed

• Fix decoding events via .as_root_event() and add test (#767)
• Retain Rust code items from mod decorated with subxt attribute (#721)

This release resolves the parity-util-mem crate several version guard by updating substrate related dependencies which makes it possible to have other substrate dependencies in tree again along with subxt.

In addition the release has several API improvements in the dynamic transaction API along with that subxt now compiles down to WASM.

Notable PRs merged:

Added

• Add getters for Module (#697)
• add wasm support (#700)
• Extend the new api.blocks() to be the primary way to subscribe and fetch blocks/extrinsics/events (#691)
• Add runtime_metadata_url to pull metadata directly from a node (#689)
• Implement BlocksClient for working with blocks (#671)
• Allow specifying the subxt crate path for generated code (#664)
• Allow taking out raw bytes from a SubmittableExtrinsic (#683)
• Add DecodedValueThunk to allow getting bytes back from dynamic queries (#680)

Changed

• Update substrate crates (#709)
• Make working with nested queries a touch easier (#714)
• Upgrade to scale-info 2.3 and fix errors (#704)
• No need to entangle Signer and nonce now (#702)
• error: RpcError with custom client error (#694)
• into_encoded() for consistency (#685)
• make subxt::Config::Extrinsic Send (#681)
• Refactor CLI tool to give room for growth (#667)
• expose jsonrpc-core client (#672)
• Upgrade clap to v4 (#678)

This release has a bunch of smaller changes and fixes. The breaking changes are fairly minor and should be easy to address if encountered. Notable additions are:

• Allowing the underlying RPC implementation to be swapped out (#634). This makes jsonrpsee an optional dependency, and opens the door for Subxt to be integrated into things like light clients, since we can decide how to handle RPC calls.
• A low level "runtime upgrade" API is exposed, giving more visibility into when node updates happen in case your application needs to handle them.
• scale-value and scale-decode dependencies are bumped. The main effect of this is that bitvec is no longer used under the hood in the core of Subxt, which helps to remove one hurdle on the way to being able to compile it to WASM.

Notable PRs merged:

Added

• feat: add low-level runtime upgrade API (#657)
• Add accessor for StaticTxPayload::call_data (#660)
• Store type name of a field in event metadata, and export EventFieldMetadata (#656 and #654)
• Allow generalising over RPC implementation (#634)
• Add conversion and default functions for NumberOrHex (#636)
• Allow creating/submitting unsigned transactions, too. (#625)
• Add Staking Miner and Introspector to usage list (#647)

Changed

• Bump scale-value and scale-decode (#659)
• Tweak 0.23 notes and add another test for events (#618)
• Specialize metadata errors (#633)
• Simplify the TxPayload trait a little (#638)
• Remove unnecessary async (#645)
• Use 'sp_core::Hxxx' for all hash types (#623)

Fixed

• Fix history_depth testing (#662)
• Fix codegen for codec::Compact as type parameters (#651)
• Support latest substrate release (#653)

This is one of the most significant releases to date in Subxt, and carries with it a number of significant breaking changes, but in exchange, a number of significant improvements. The most significant PR is #593; the fundamental change that this makes is to separate creating a query/transaction/address from submitting it. This gives us flexibility when creating queries; they can be either dynamically or statically generated, but also flexibility in our client, enabling methods to be exposed for online or offline use.

The best place to look to get a feel for what's changed, aside from the documentation itself, is the examples folder. What follows are some examples of the changes you'll need to make, which all follow a similar pattern:

Submitting a transaction

Previously, we'd build a client which is tied to the static codegen, and then use the client to build and submit a transaction like so:

let api = ClientBuilder::new()
    .build()
    .await?
    .to_runtime_api::<polkadot::RuntimeApi<DefaultConfig, PolkadotExtrinsicParams<_>>>();

let balance_transfer = api
    .tx()
    .balances()
    .transfer(dest, 10_000)?
    .sign_and_submit_then_watch_default(&signer)
    .await?
    .wait_for_finalized_success()
    .await?;

Now, we build a transaction separately (in this case, using static codegen to guide us as before) and then submit it to a client like so:

let api = OnlineClient::<PolkadotConfig>::new().await?;

let balance_transfer_tx = polkadot::tx().balances().transfer(dest, 10_000);

let balance_transfer = api
    .tx()
    .sign_and_submit_then_watch_default(&balance_transfer_tx, &signer)
    .await?
    .wait_for_finalized_success()
    .await?;

See the examples/examples/submit_and_watch.rs example for more.

Fetching a storage entry

Previously, we build and submit a storage query in one step:

let api = ClientBuilder::new()
    .build()
    .await?
    .to_runtime_api::<polkadot::RuntimeApi<DefaultConfig, PolkadotExtrinsicParams<DefaultConfig>>>();

let entry = api.storage().staking().bonded(&addr, None).await;

Now, we build the storage query separately and submit it to the client:

let api = OnlineClient::<PolkadotConfig>::new().await?;

let staking_bonded = polkadot::storage().staking().bonded(&addr);

let entry = api.storage().fetch(&staking_bonded, None).await;

Note that previously, the generated code would do the equivalent of fetch_or_default if possible, or fetch if no default existed. You must now decide whether to:

• fetch an entry, returning None if it's not found (api.storage().fetch(..)), or
• fetch an entry, returning the default if it's not found (api.storage().fetch_or_default(..)).

The static types will protect you against using fetch_or_default when no such default exists, and so the recommendation is to try changing all storage requests to use fetch_or_default, falling back to using fetch where doing so leads to compile errors.

See examples/examples/concurrent_storage_requests.rs for an example of fetching entries.

Iterating over storage entries

Previously:

let api = ClientBuilder::new()
    .build()
    .await?
    .to_runtime_api::<polkadot::RuntimeApi<DefaultConfig, PolkadotExtrinsicParams<DefaultConfig>>>();

let mut iter = api
    .storage()
    .xcm_pallet()
    .version_notifiers_iter(None)
    .await?;

while let Some((key, value)) = iter.next().await? {
    // ...
}

Now, as before, building the storage query to iterate over is separate from using it:

let api = OnlineClient::<PolkadotConfig>::new().await?;

let key_addr = polkadot::storage()
    .xcm_pallet()
    .version_notifiers_root();

let mut iter = api
    .storage()
    .iter(key_addr, 10, None).await?;

while let Some((key, value)) = iter.next().await? {
    // ...
}

Note that the _root() suffix on generated storage queries accesses the root entry at that address, and is available when the address is a map that can be iterated over. By not appending _root(), you'll be asked to provide the values needed to access a specific entry in the map.

See the examples/examples/storage_iterating.rs example for more.

Accessing constants

Before, we'd build a client and use the client to select and query a constant:

let api = ClientBuilder::new()
    .build()
    .await?
    .to_runtime_api::<polkadot::RuntimeApi<DefaultConfig, PolkadotExtrinsicParams<DefaultConfig>>>();

let existential_deposit = api
    .constants()
    .balances()
    .existential_deposit()?;

Now, similar to the other examples, we separately build a constant address and provide that address to the client to look it up:

let api = OnlineClient::<PolkadotConfig>::new().await?;

let address = polkadot::constants()
    .balances()
    .existential_deposit();

let existential_deposit = api.constants().at(&address)?;

See the examples/examples/fetch_constants.rs example for more.

Subscribing to events

Event subscriptions themselves are relatively unchanged (although the data you can access/get back has changed a little). Before:

let api = ClientBuilder::new()
    .build()
    .await?
    .to_runtime_api::<polkadot::RuntimeApi<DefaultConfig, PolkadotExtrinsicParams<DefaultConfig>>>();

let mut event_sub = api.events().subscribe().await?;

while let Some(events) = event_sub.next().await {
    // ...
}

Now, we simply swap the client out for our new one, and the rest is similar:

let api = OnlineClient::<PolkadotConfig>::new().await?;

let mut event_sub = api.events().subscribe().await?;

while let Some(events) = event_sub.next().await {
    // ...
}

Note that when working with a single event, the method event.bytes() previously returned just the bytes associated with the event fields. Now, event.bytes() returns all of the bytes associated with the event. There is a separate method, event.field_bytes(), that returns the bytes for just the fields in the event. This change will not lead to a compile error, and so it's worth keeping an eye out for any uses of .bytes() to update them to .field_bytes().

See the examples/examples/subscribe_all_events.rs example for more.

The general pattern, as seen above, is that we break apart constructing a query/address and using it. You can now construct queries dynamically instead and forego all static codegen by using the functionality exposed in the subxt::dynamic module instead.

Other smaller breaking changes have happened, but they should be easier to address by following compile errors.

For more details about all of the changes, the full commit history since the last release is as follows:

Added

• Expose the extrinsic hash from TxProgress (#614)
• Add support for ws in subxt-cli (#579)
• Expose the SCALE encoded call data of an extrinsic (#573)
• Validate absolute path for substitute_type (#577)

Changed

• Rework Subxt API to support offline and dynamic transactions (#593)
• Use scale-decode to help optimise event decoding (#607)
• Decode raw events using scale_value and return the decoded Values, too (#576)
• dual license (#590)
• Don't hash constant values; only their types (#587)
• metadata: Exclude field::type_name from metadata validation (#595)
• Bump Swatinem/rust-cache from 1.4.0 to 2.0.0 (#597)
• Update jsonrpsee requirement from 0.14.0 to 0.15.1 (#603)

With this release, subxt can subscribe to the node's runtime upgrades to ensure that the metadata is updated and extrinsics are properly constructed.

We have also made some slight API improvements to make in the area of storage keys, and thanks to an external contribution we now support dry running transactions before submitting them.

This release also improves the documentation, adds UI tests, and defaults the subxt-cli to return metadata bytes instead of the JSON format.

Fixed

• Handle StorageEntry empty keys (#565)
• Fix documentation examples (#568)
• Fix cargo clippy (#548)
• fix: Find substrate port on different log lines (#536)

Added

• Followup test for checking propagated documentation (#514)
• feat: refactor signing in order to more easily be able to dryrun (#547)
• Add subxt documentation (#546)
• Add ability to iterate over N map storage keys (#537)
• Subscribe to Runtime upgrades for proper extrinsic construction (#513)

Changed

• Move test crates into a "testing" folder and add a ui (trybuild) test and ui-test helpers (#567)
• Update jsonrpsee requirement from 0.13.0 to 0.14.0 (#566)
• Make storage futures only borrow client, not self, for better ergonomics (#561)
• Bump actions/checkout from 2 to 3 (#557)
• Deny unused crate dependencies (#549)
• Implement Clone for the generated RuntimeApi (#544)
• Update color-eyre requirement from 0.5.11 to 0.6.1 (#540)
• Update jsonrpsee requirement from 0.12.0 to 0.13.0 (#541)
• Update artifacts and polkadot.rs and change CLI to default bytes (#533)
• Replace log with tracing and record extrinsic info (#535)
• Bump jsonrpsee (#528)

This release adds static metadata validation, via comparing the statically generated API with the target node's runtime metadata. This implies a breaking change in the subxt API, as the user receives an error when interacting with an incompatible API at the storage, call, and constant level.

The subxt-cli can check the compatibility of multiple runtime nodes, either full metadata compatibility or compatibility at the pallet level.

Users can define custom derives for specific generated types of the API via adding the derive_for_type configuration to the subxt attribute.

The metadata documentation is propagated to the statically generated API.

Previously developers wanting to build the subxt crate needed the substrate binary dependency in their local environment. This restriction is removed via moving the integration tests to a dedicated crate.

The number of dependencies is reduced for individual subxt crates.

Fixed

• test-runtime: Add exponential backoff (#518)

Added

• Add custom derives for specific generated types (#520)
• Static Metadata Validation (#478)
• Propagate documentation to runtime API (#511)
• Add tidext in real world usage (#508)
• Add system health rpc (#510)

Changed

• Put integration tests behind feature flag (#515)
• Use minimum amount of dependencies for crates (#524)
• Export BaseExtrinsicParams (#516)
• bump jsonrpsee to v0.10.1 (#504)