scale-decode-derive

0.15.0 - 2024-11-08

This release makes scale-decode entirely no_std which is now using core::error::Error instead of std::error::Error as it was using before behind
the std feature. Because of that the std feature is now removed and the MSRV is bumped to 1.81.0.

Changed

• chore(deps): bump syn from 1.0 to 2.0 (#60)
• chore(deps): bump primitives types from 0.12.0 to 0.13.1 (#61)
• chore(deps): chore(deps): bump derive_more from 0.99 to 1.0.0 (#62)

0.13.2 - 2024-10-21

Changed

• chore(deps): bump syn from 1.0 to 2.0 (#60)
• chore(deps): bump primitives types from 0.12.0 to 0.13.1 (#61)
• chore(deps): chore(deps): bump derive_more from 0.99 to 1.0.0 (#62)

Full Changelog: v0.13.1...v0.13.2

Prep for 0.13.1 release (#59)

0.13.0 - 2023-05-15

This minor release avoids a couple of panics in the case of invalid bytes being interpreted as BitVecs or strings.

A small API change was made to accommodate this, such that the Str::bytes_after now returns a result rather than just the bytes.

Fixed

• Avoid panic on invalid bitvec input bytes (#53
• Avoid panic on invalid str input bytes (#54)

0.12.0 - 2024-04-29

Update the scale-type-resolver dependency to 0.2.0 (and bump scale-bits for the same reason).

The main changes here are:

• Type IDs are now passed by value rather than reference.
• The Composite type handed back in the visitor's visit_composite() method now exposes the name and path of the composite type being decoded, if one was provided.

0.11.1 - 2023-02-16

• scale-info was still being pulled in via scale-type-resolver; this has now been fixed

0.11.0 - 2023-02-09

Up until now, this crate depended heavily on scale_info to provide the type information that we used to drive our decoding of types. This release removes the explicit dependency on scale-info, and instead depends on scale-type-resolver, which offers a generic TypeResolver trait whose implementations are able to provide the information needed to decode types (see this PR for more details). So now, the traits and types in scale-decode have been made generic over which TypeResolver is used to help decode things. scale-info::PortableRegistry is one such implementation of TypeResolver, and so can continue to be used in a similar way to before.

The main breaking changes are:

Visitor trait

The scale_decode::Visitor trait now has an additional associated type, TypeResolver.

The simplest change to recover the previous behaviour is to just continue to use scale_info::PortableRegistry for this task, as was the case implicitly before:

struct MyVisitor;

impl Visitor for MyVisitor {
  // ...
  type TypeResolver = scale_info::PortableRegistry;

  // ...
}

A better change is to make your Visitor impls generic over what is used to resolve types unless you need a specific resolver:

struct MyVisitor<R>(PhantomData<R>);

impl <R> MyVisitor<R> {
  pub fn new() -> Self {
    Self(PhantomData)
  }
}

impl <R: TypeResolver> Visitor for MyVisitor<R> {
  // ...
  type TypeResolver = R;

  // ...
}

IntoVisitor trait

scale_decode::IntoVisitor is implemented on all types that have an associated Visitor that we can use to decode it. It used to look like this:

pub trait IntoVisitor {
    type Visitor: for<'scale, 'resolver> visitor::Visitor<
        Value<'scale, 'resolver> = Self,
        Error = Error,
    >;
    fn into_visitor() -> Self::Visitor;
}

Now it looks like this:

pub trait IntoVisitor {
    type AnyVisitor<R: TypeResolver>: for<'scale, 'resolver> visitor::Visitor<
        Value<'scale, 'resolver> = Self,
        Error = Error,
        TypeResolver = R,
    >;
    fn into_visitor<R: TypeResolver>() -> Self::AnyVisitor<R>;
}

What this means is that if you want to implement IntoVisitor for some type, then your Visitor must be able to accept any valid TypeResolver. This allows DecodeAsType to also be generic over which TypeResolver is provided.

DecodeAsType

This trait previously was specific to scale_info::PortableRegistry and looked something like this:

pub trait DecodeAsType: Sized + IntoVisitor {
    fn decode_as_type<R: TypeResolver>(
        input: &mut &[u8],
        type_id: u32,
        types: &scale_info::PortableRegistry,
    ) -> Result<Self, Error> {
        // ...
    }

Now, it is generic over which type resolver to use (and as a side effect, requires a reference to the type_id now, because it may not be Copy any more):

pub trait DecodeAsType: Sized + IntoVisitor {
    fn decode_as_type<R: TypeResolver>(
        input: &mut &[u8],
        type_id: &R::TypeId,
        types: &R,
    ) -> Result<Self, Error> {
        // ...
    }

This is automatically implemented for all types which implement IntoVisitor, as before.

Composite and Variant paths

Mostly, the changes just exist to make things generic over the TypeResolver. One consequence of this is that Composite and Variant types no longer know their path, because currently TypeResolver doesn't provide that information (since it's not necessary to the actual encoding/decoding of types). If there is demand for this, we can consider allowing TypeResolver impls to optionally provide these extra details.

0.10.0 - 2023-11-10

This release changes IntoVisitor to require that the corresponding Visitor implements scale_decode::Error, rather than allowing the error to be anything that can be converted into a scale_decode::Error. This has the following advantages:

• It makes DecodeAsType a proper super-trait of IntoVisitor, meaning it can be used anywhere IntoVisitor is. Previously, using DecodeAsType in some places also required that you add a bound like B: IntoVisitor, <B::Visitor as Visitor>::Error: Into<scale_decode::Error, ie the Error type needed to explicitly be declared as convertible in the way that DecodeAsType requires.
• It simplifies the code.
• It makes it a bit easier to understand how to correctly make a type implement DecodeAsType.

The main drawback is that if your Visitor implementation doesn't have Error = scale_decode::Error, then it can no longer be used with IntoVisitor. To work around this, a new adapter type, scale_decode::visitor::VisitorWithCrateError(your_visitor) has been added; any visitor wrapped in this type whose error implements Into<scale_decode::Error> will now implement Visitor with Error = scale_decode::Error.

• Change how compact encoding is handled: visit_compact_* functions are removed from the Visitor trait, and compact encoding is now handled recursively and should now work in more cases (such as nested structs with compact encoded values inside) (#32).
• Improve custom error handling: custom errors now require Debug + Display on no_std or Error on std. Error::custom() now accepts anything implementing these traits rather than depending on Into<Error> (#31).

• Add support for no_std (+alloc) builds (#26). Thankyou @haerdib!

• Change DecodeAsFields again; remove the generic iterator parameter and use &mut dyn FieldIter instead. This Simplifies the call signatures in a bunch of places and is consistent with how scale-encode works.
• Use smallvec instead of our own stack allocated vec.

• Change DecodeAsFields to accept an iterator of fields to decode into. This makes it more flexible in what it is able to decode. This bleeds into various other types, which inherit a generic parameter to represent this iterator that is used to drive decoding.

This release shifts scale-decode to being a mirror of a new scale-encode crate, and:

• Adds a new IntoVisitor trait that types can implement if there is a Visitor which can be used to decode into them.
• Adds a new DecodeAsType trait to mirror the EncodeAsType trait there; any type that implements IntoVisitor automatically implements DecodeAsType.
• Adds a new DecodeAsFields trait to mirror EncodeAsFields, implemented for tuple and struct types.
• Moves the Visitor trait into a sub module and re-works the interface to allow zero copy decoding, allow more concise implementations of it, and provide a fallback escape hatch to allow for more arbitrary DecodeAsType implementations from it.
• Implements DecodeAsType (via Visitor and IntoVisitor impls) and DecodeAsFields on common types.
• Adds a DecodeAsType derive macro to auto-generate impls on custom struct and enum types.

Any Visitor impls will need to be updated to use the refined Visitor trait; this should be fairly mechanical (check out the examples and follow the compiler guidance to do this). Otherwise, the rest of the changes are additive and just make it easier to implement this trait and obtain a DecodeAsType implementation, if desired.

Changed

• Add DecodeAsType backed by Visitor impls for standard types. (#11)