cached_proc_macro_types changelog and release notes

Additional notes

This entry describes the complete 2.0.2 -> 3.0.0 delta. The ten release candidates (3.0.0-rc.1 through 3.0.0-rc.10) are folded in here, and API that was introduced and then changed again across the candidates is recorded only in its final shipped form; the rc git tags remain. The upgrade is documented step by step in the migration guide, with the mechanical breaking-change list in the agent-oriented guide.

Breaking Changes

Minimum supported Rust version

MSRV raised from 1.85 to 1.92. redb 4.x set the 1.89 floor, and the async_core feature (enabled by async) does not compile before 1.92: the two CachedGetOrSetAsync RPIT default bodies hit a rustc borrowck limitation (rust-lang/rust#100013). Verified by bisection (fails on 1.89.0, 1.90.0, 1.91.0; clean on 1.92.0). Non-async feature sets built on 1.89, but rust-version is a single crate-level value, so the floor moves for every feature set.
cached_proc_macro_types moved to edition 2024, and its version now tracks cached in lockstep rather than a standalone 1.0.

Store renames and the disk backend (#237)

DiskCache is renamed RedbCache (naming the backend, like RedisCache) and is backed by redb 4.x instead of the unmaintained sled, dropping the RustSec-flagged fxhash transitive dependency. Still pure-Rust (no C toolchain). There are no DiskCache* aliases: rename DiskCache / DiskCacheBuilder / DiskCacheError / DiskCacheBuildError to RedbCache* at the call site. The on-disk format changed and DISK_FILE_VERSION was bumped, so existing caches are not read and entries are recomputed.
RedbCache::connection() / connection_mut(), RedbCacheBuilder::connection_config, and the connection_config macro attribute are removed; the backend handle is not exposed.
DiskCacheBuilder::sync_to_disk_on_cache_change is renamed durable and the default flipped from false to true (fsync per write), so a disk cache persists by default. durable(false) uses Durability::None, which can lose writes on process exit or crash; call RedbCache::flush() / async_flush() to force a durable commit.
RedbCacheBuilder::disk_directory is renamed disk_dir, matching the disk_dir attribute on #[concurrent_cached].
ShardedCache is renamed ShardedUnboundCache (with ShardedCacheBuilder -> ShardedUnboundCacheBuilder); the old name read as the umbrella for the whole sharded family while naming only the unbounded variant. No deprecated alias.
The six sharded stores are single types carrying a defaulted hasher parameter, ShardedX<K, V, H = DefaultShardHasher>, mirroring HashMap<K, V, S = RandomState>. The 2.x ShardedCacheBase pattern is gone: there is no ShardedUnboundCacheBase, ShardedLruCacheBase, ShardedTtlCacheBase, ShardedLruTtlCacheBase, ShardedExpiringCacheBase, or ShardedExpiringLruCacheBase. Migration is a mechanical rename dropping Base.
cached::TimedEntry is now pub(crate), and the store() accessors on UnboundCache, TtlCache, LruTtlCache, and ExpiringLruCache are removed. They exposed the internal backing map and leaked the internal entry wrapper; use the public Cached API instead.

Trait surface

The short method aliases (get, set, remove, remove_entry, clear, len, is_empty, delete, try_set, contains, hits, misses, metrics, and the short get_or_set_with family) moved off Cached / ConcurrentCached onto the blanket extension traits CachedExt / ConcurrentCachedExt. The core traits keep only the cache_-prefixed methods, so a custom store implements a smaller surface. Callers using cached::prelude::* need no change; others add use cached::CachedExt; / use cached::ConcurrentCachedExt;, or use the cache_ names. Custom impl Cached / impl ConcurrentCached blocks must drop any short-alias methods.
ConcurrentCachedAsync's cache operations carry an async_ prefix (async_cache_get, async_cache_set, async_cache_remove, async_cache_remove_entry, async_cache_delete), removing the E0034 "multiple applicable items" error when both concurrent traits are in scope.
The concurrent trait surface is split. Introspection (type Error, cache_size, cache_is_empty) lives on ConcurrentCacheBase, the supertrait of both concurrent traits; the global-TTL controls (ttl, set_ttl, try_set_ttl, unset_ttl) live on ConcurrentCacheTtl, implemented only by the TTL-capable concurrent stores. len is removed from the base trait as a duplicate of cache_size. Custom impls must move type Error (and any size override) into an impl ConcurrentCacheBase block and TTL behavior into impl ConcurrentCacheTtl.
refresh_on_hit / set_refresh_on_hit live on their own CacheRefreshOnHit and ConcurrentCacheRefreshOnHit traits rather than on CacheTtl / ConcurrentCacheTtl. CacheRefreshOnHit is implemented by TtlCache and LruTtlCache; ConcurrentCacheRefreshOnHit by RedisCache, AsyncRedisCache, RedbCache, ShardedTtlCache, and ShardedLruTtlCache. TtlSortedCache implements neither: its deadline-ordered index cannot refresh an entry's expiry on read, and its 2.x set_refresh_on_hit was a no-op that discarded its argument. Both new traits are in the prelude. The inherent refresh_on_hit / set_refresh_on_hit on TtlCache and LruTtlCache are removed (they shadowed the trait methods and the setter returned ()), as are the inherent TTL controls on the sharded TTL stores and TtlSortedCache::set_ttl: runtime TTL control is trait-only.
CacheTtl and CacheEvict are single-owner (&mut self) traits only, since &mut self is unusable on a store held through Arc/static. Concurrent stores set TTL through ConcurrentCacheTtl::set_ttl (&self) and evict through the new ConcurrentCacheEvict (fn evict(&self) -> usize).
Cached and ConcurrentCacheBase gained an associated type Error, bounded by std::error::Error + Send + Sync + 'static. Every built-in in-memory store (UnboundCache, LruCache, TtlCache, LruTtlCache, TtlSortedCache, ExpiringCache, ExpiringLruCache, and the six sharded stores) is infallible: type Error = std::convert::Infallible. A TTL that would overflow Instant bounds stores the entry with no expiry instead of failing, so cache_try_set no longer has a dedicated error type; the 2.x TtlSortedCacheError and the boxed Box<dyn std::error::Error> return are both gone.
Cached::cache_get_or_set_with / cache_try_get_or_set_with (and their aliases) return &V / Result<&V, E> instead of &mut V (#179). The new *_mut variants (cache_get_or_set_with_mut, cache_try_get_or_set_with_mut, and the async spellings) preserve the mutable-reference behavior. External impls must update their signatures and implement the new required *_mut methods.
The 2.x CachedAsync trait is renamed CachedGetOrSetAsync, naming the job it actually does (memoizing an async closure over a synchronous in-memory Cached store). Its four sync passthroughs (async_cache_get / async_cache_set / async_cache_remove / async_cache_clear) and the misleading Self: Cached bound are removed, and its get-or-set methods use the async_cache_* namespace (async_cache_get_or_set_with, async_cache_try_get_or_set_with, and their _mut variants).
New required methods on custom impls: cache_clear / cache_reset on ConcurrentCached (and the async counterparts), whose 2.x no-op Ok(()) defaults silently did nothing; cache_peek_with_expiry_status on CloneCached / ConcurrentCloneCached, whose defaults returned a wrong result that silently broke force_refresh + result_fallback; and cache_contains / async_cache_contains on ConcurrentCached / ConcurrentCachedAsync, which carry no V: Clone bound so contains works for non-Clone values. ConcurrentCached::cache_contains has no where Self: Sized bound and is dyn-callable.
SerializeCached::cache_set_ref and SerializeCachedAsync::async_cache_set_ref return Result<(), Self::Error> instead of Result<Option<V>, Self::Error>, removing a per-write read-and-decode round trip on the IO stores. Call cache_get first if you need the prior value.
ShardHasher requires Clone as a supertrait, and any thread-safe std::hash::BuildHasher now implements it through a blanket impl, so std::hash::RandomState and ahash::RandomState are accepted directly by the sharded builders' .hasher(...). DefaultShardHasher implements BuildHasher and reaches ShardHasher through that one blanket path, which also makes it usable with HashMap::with_hasher and LruCacheBuilder::hasher. A type cannot implement both BuildHasher and a hand-written ShardHasher (coherence rejects the pair), so a custom shard-routing hasher must not implement BuildHasher.
Expires::expires_at returns crate::time::Instant (web-time backed, correct under wasm) instead of std::time::Instant, and CloneCached::cache_get_with_expiry_status requires V: Clone, matching its peek sibling.

Store behavior

cache_set over an existing key promotes that key to most-recently-used on LruCache, LruTtlCache, ExpiringLruCache, ShardedLruCache, ShardedLruTtlCache, and ShardedExpiringLruCache. In 2.x the value was replaced in place and the entry kept its position, so this changes which entry a capacity eviction selects in overwrite-heavy workloads. It also resolves a divergence where configuring an on_evict callback changed eviction order on two sharded stores. cache_peek, cache_peek_with_expiry_status, and cache_contains remain non-promoting; inserting a new key is unchanged. No public API writes a value without touching recency.
on_evict receives the displaced entry's own stored key rather than the caller's Eq-equal instance, on every store and every removal path, matching HashMap::insert. Observable only for key types whose Eq/Hash ignore part of the payload.
Every store counts an eviction before firing on_evict, on every removal path (evict, retain, cache_remove / cache_remove_entry, lazy expiry sweeps, cache_set over an expired entry, capacity evictions, and the get-or-set families), so a panicking callback can no longer remove an entry without counting it.
retain returns usize (the number of entries removed) instead of () on all 13 stores that have it. The count includes entries the predicate rejected and, on the expiry-aware stores, entries removed for having expired regardless of the predicate. This diverges from HashMap::retain deliberately, because this retain does strictly more than filter, and it matches TtlSortedCache::retain_latest. There is no #[must_use], so existing cache.retain(...); statements keep compiling; only call sites binding the result as () need a discard.
set_max_size returns Option<usize> (the previous bound) on LruCache, LruTtlCache, and ExpiringLruCache, unifying the return type with TtlSortedCache.
The default shard count of the LRU-bounded sharded stores (ShardedLruCache, ShardedLruTtlCache, ShardedExpiringLruCache) is capped by the requested max_size instead of derived solely from available_parallelism(): on the default path the count is next_power_of_two(max_size / 16).clamp(1, default_shard_count()). This changes the observable capacity(), shards(), and shard_sizes() for small caches on high-core-count hosts (ShardedLruCache::new(100) resolves to 8 shards / capacity 128, where a 64-core box previously produced 256 shards / capacity 4096). An explicit .shards(n) is authoritative; the per_shard_max_size path and the unbounded stores keep default_shard_count().
ShardedTtlCache and ShardedLruTtlCache decide expiry against a clock sample taken before the shard lock is acquired, so an entry that crosses its expiry while the caller queues for the lock is judged live. This stays within the documented lazy-expiry contract, which makes no promise of prompt removal.
TTL stores track per-entry expiry, so set_ttl applies to future inserts only; existing entries keep their computed expiry, and refresh_on_hit recomputes expiry from the current TTL at access time. A zero Duration passed to any set_ttl surface means "expiry disabled", exactly equivalent to unset_ttl(): it no longer panics on the sharded stores and no longer means "expire immediately" on TtlSortedCache. build() still rejects a zero TTL, and try_set_ttl(0) still returns SetTtlError::ZeroTtl. For the redis stores a disabled TTL writes keys without expiry (a plain SET) and the refresh path issues no EXPIRE.
TtlSortedCache gains a set family in place of insert / insert_ttl / insert_evict / insert_ttl_evict: set(k, v) plus the set_with(k, v) entry-setter builder, which chains .ttl(Duration) / .ttl_secs(n) / .ttl_millis(n) for a per-entry override and .evict() for the post-insertion sweep before the terminal .set() -> Option<V>. TtlSortedSetBuilder is re-exported from the crate root.
TtlSortedCache's get-or-set family no longer removes an expired entry before running the initializer, so a cancelled or panicking initializer leaves the expired entry in place and fires no on_evict; on success on_evict fires after the initializer. All four variants now agree with each other and with TtlCache / LruTtlCache.
iter_order / value_order on LruCache, LruTtlCache, and ExpiringLruCache return CacheValue-wrapped values (Vec<(K, CacheValue<V, M>)> and Vec<CacheValue<V, M>>), one shape across the LRU family. M is per-entry metadata: () for LruCache / ExpiringLruCache, Option<Instant> for LruTtlCache (read through CacheValue::expires_at). LruTtlCache no longer leaks bare (Option<Instant>, V) tuples. key_order is unchanged.
cache_reset (and the concurrent counterparts) no longer preserves the preallocated backing capacity: it clears and shrinks to initial_capacity, so later inserts may reallocate. Recreate the cache instead of resetting it to retain the allocation.
Sharded copy_from returns Result<_, BuildError> instead of panicking on invalid configuration, and the Eq marker impls for UnboundCache and LruCache require V: Eq.
The six sharded types expose inherent get / set / remove / remove_entry / delete / reset / contains / peek returning unwrapped values, so store.get(&k) is Option<V> rather than Result<Option<V>, Infallible>. These take call-site priority over the ConcurrentCached* trait methods, which return Result<_, Self::Error>; note that s.set(k, v).unwrap() therefore compiles as Option::unwrap and panics on a first insert. Use the cache_-prefixed trait methods, or UFCS, for the Result shape.

Builders

capacity(n) is renamed initial_capacity(n) on UnboundCacheBuilder, TtlCacheBuilder, TtlSortedCacheBuilder, and ExpiringCacheBuilder, where it pre-allocates without bounding entry count. The name was ambiguous next to max_size(n) on the LRU builders.
RedbCache::builder(name), RedisCache::builder(prefix), and AsyncRedisCache::builder(prefix) take the primary required field as a positional argument. The 2.x ::new( entry points on these three types are removed (they returned a builder, conflicting with the convention that new() returns a ready store); the in-memory and sharded stores gained real Type::new() / Type::new(required_field) constructors.
LruTtlCacheBuilder and ShardedLruTtlCacheBuilder take the hasher in the third generic slot and the eviction typestate marker last: LruTtlCacheBuilder<K, V, S = DefaultHashBuilder, E = NoEvict> and ShardedLruTtlCacheBuilder<K, V, H = DefaultShardHasher, E = NoEvict>. LruTtlCacheBuilder had no hasher parameter in 2.x, so a 2.x annotation of LruTtlCacheBuilder<K, V, HasEvict> names the hasher slot in 3.0 and must gain the hasher as the third argument. Code naming only <K, V>, or reaching the hasher through .hasher(..), is unaffected.
The redis TTL is optional: omitting .ttl(...) stores keys without expiry. A TTL that is set must be greater than zero, and RedisCacheBuildError::MissingRequired("ttl") is no longer returned.
RedisCacheBuilder::build() / AsyncRedisCacheBuilder::build() reject an empty prefix with Build(BuildError::InvalidValue { field: "prefix", .. }). The prefix is what scopes cache_clear to one logical cache; with an empty prefix, cache_clear matched <namespace>:* and deleted the entries of every cache sharing the namespace.
RedbCacheBuilder::build() validates cache_name as a filename component: empty, path separators, path-traversal components, and any character invalid in a cross-platform filename (: < > " | ? *, or an ASCII control byte) are rejected rather than silently creating subdirectories or escaping the cache directory.
Builder refresh naming is unified on refresh_on_hit: the refresh() alias is removed from the in-memory TTL builders, and the redis/redb builders' refresh is renamed. The #[cached(refresh = true)] attribute is unchanged.
BuildError::InvalidTtl { ttl } is removed; a zero TTL at build time yields BuildError::InvalidValue { field: "ttl", reason: "must be greater than zero" }. RedisCacheBuildError::InvalidTtl and RedbCacheBuildError::InvalidTtl become Build(BuildError), wrapping the inner error instead of duplicating it.

Error and metrics types

Error enum variants dropped their redundant Error suffix: RedbCacheError::{StorageError, CacheDeserializationError, CacheSerializationError} became {Storage, CacheDeserialization, CacheSerialization}; RedbCacheBuildError::ConnectionError became Storage; RedisCacheError::{RedisCacheError, PoolError, CacheDeserializationError, CacheSerializationError} became {Redis, Pool, CacheDeserialization, CacheSerialization}. RedbCacheError / RedbCacheBuildError are struct variants (named fields) matching the redis enums, and CacheDeserialization carries a cached_value: Vec<u8> field.
The public store error enums (RedbCacheError, RedbCacheBuildError, RedisCacheError, RedisCacheBuildError, BuildError, SetTtlError, SetMaxSizeError) are #[non_exhaustive], so external matches need a wildcard arm.
The redis and redb error types no longer expose redis::, r2d2::, or redb:: types through public fields or blanket From impls. Foreign causes are boxed behind Box<dyn std::error::Error + Send + Sync> and read through source(), so a backing-crate version bump is no longer a breaking change to these enums.
Return<T>::value and Return<T>::was_cached are private fields (cached_proc_macro_types). Use *r / r.into_inner() for the value and r.was_cached() for the flag; struct pattern matches must switch to the accessors.
CacheMetrics.size is renamed entry_count and is now Option<usize>, reporting None for stores whose size is unknown (redis/redb) instead of a false 0. CacheMetrics is #[non_exhaustive] and derives Default, so construct it by mutating CacheMetrics::default() rather than with a struct literal.
RedbCache::remove_expired_entries returns Result<usize, RedbCacheError> (the number removed) instead of Result<(), RedbCacheError>, matching the evict traits.

Macros

The ttl attribute takes three mutually exclusive forms: ttl_secs = N (whole seconds, replacing the 2.x bare-integer ttl = N), ttl_millis = N (milliseconds, new), and ttl = "<Duration expr>" (a string-literal Duration expression). The old bare-integer form produces an error directing you to ttl_secs. Builders gained matching .ttl_secs(n) / .ttl_millis(n) methods (#149).
The deprecated size attribute is removed from #[cached] / #[concurrent_cached] (use max_size = N; the macros detect size and emit a directed error), and the unbound attribute is removed from #[cached] (a bare #[cached] already builds an UnboundCache).
#[cached(refresh = true)] without a TTL is a compile error; it was previously ignored. #[cached] also rejects result_fallback combined with with_cached_flag, and rejects an explicit sync_writes_buckets when sync_writes is not "by_key" (the value was accepted and silently ignored).
#[cached] / #[once] reject the concurrent-store-only attributes (disk, redis, map_error, shards, durable, disk_dir, cache_prefix_block) with a targeted redirect to #[concurrent_cached], and #[once] rejects the #[cached]-only attributes (result_fallback, refresh, max_size, ty, create, key, convert, sync_lock, unsync_reads, sync_writes_buckets). #[concurrent_cached] rejects a custom ty without a create block on the redis and disk paths, an async closure for map_error, and cache_prefix_block on the disk path (it is redis-only).
All three macros reject a name starting with __cached (the prefix reserved for generated bindings) and validate name as a Rust identifier.
#[concurrent_cached]'s refresh attribute is a plain bool (was Option<bool>), so refresh = false no longer conflicts with expires or a create block.

Features and runtime

Redis TLS is a separate axis (#231): redis_tokio and redis_smol enable the TLS-agnostic connection path, so add redis_tokio_native_tls / redis_tokio_rustls (or the redis_smol equivalents) to restore TLS. redis_connection_manager and redis_async_cache are capability features depending only on redis/aio, so they are runtime-agnostic and must be paired with a runtime feature; the connection manager is a per-cache .connection_manager(true) opt-in rather than a feature that cfg-swapped every cache's connection type.
The disk_store feature is renamed redb_store. The wasm feature is removed (it gated nothing; web-time provides wasm-compatible time types transparently), as are redis_ahash and async_tokio_rt_multi_thread.
The async feature no longer implies tokio; it pulls only async-lock, and cached::async_sync::{Mutex, RwLock, OnceCell} re-export from async-lock instead of tokio::sync (OnceCell there has no const_new()). Async RedbCache runs blocking redb work on the blocking crate's thread pool instead of tokio::spawn_blocking, and RedbCacheError::BackgroundTaskFailed is removed. blocking is pulled by redb_store rather than async, so redis-only and in-memory async builds do not pay for it.
Optional dependencies are gated with Cargo's dep: syntax, so an optional dependency's name is no longer silently usable as a feature; enable the named crate feature instead.
Redis values are serialized with MessagePack (rmp-serde) instead of JSON. Old 2.x JSON entries are read transparently and rewritten as MessagePack on their next write. Redis TTLs use PSETEX / PEXPIRE, so sub-second TTLs are honored to the millisecond (requires Redis 2.6+).
Redis key segments are percent-escaped (: -> %3A, % -> %25) and the key always has three fields ({namespace}:{prefix}:{key}), so distinct triples always map to distinct keys; an unescaped join previously let namespace="a:b", prefix="" collide with namespace="a", prefix="b". An empty prefix keeps its separator: ("ns", "", "k") encodes as ns::k. This changes the on-wire key for any segment containing : or %; the value envelope's version field does not cover key layout, so an old entry is not found after upgrading, is recomputed and rewritten at the new key, and the old entry expires on its original TTL.
RedisCache::connection_string() / AsyncRedisCache::connection_string() return a ConnectionString newtype whose Display and Debug redact credentials; call .reveal() for the raw URL.
The ahash feature enables ahash/runtime-rng on non-wasm targets, seeding hash maps from the OS RNG instead of a compile-time seed (hash-flood resistance). wasm32 keeps the compile-time seed. No source change required.

Added

cached::prelude re-exports the common traits plus the CacheMetrics struct for a single glob import.
Custom hashers on the non-sharded in-memory stores: UnboundCache, LruCache, TtlCache, LruTtlCache, TtlSortedCache, ExpiringCache, and ExpiringLruCache gained a hasher type parameter defaulted to DefaultHashBuilder and a .hasher(s) builder method, mirroring the sharded stores. DefaultHashBuilder is re-exported from the crate root.
Builder::new() on all 13 in-memory and sharded builders, matching the IO builders' public constructors.
CacheValue<V, M = ()>: the value-plus-metadata wrapper returned by the LRU-family order methods, re-exported from the crate root. Deref<Target = V>, PartialEq<V> against bare values, Display where V: Display, value() / into_value(), and expires_at() when M = Option<Instant>. IntoValues::into_values() bulk-unwraps an iter_order() / value_order() result back into a plain Vec<V>. The reverse comparison bare_value == wrapped cannot be implemented: coherence forbids the blanket impl.
retain(keep) across every in-memory store: UnboundCache, LruCache, TtlCache, LruTtlCache, TtlSortedCache, ExpiringCache, ExpiringLruCache, and the six sharded stores. Every removed entry fires on_evict; on the expiry-aware stores expired entries are removed regardless of the predicate and every removal counts an eviction. The sharded form locks one shard at a time (not atomic across shards), runs the predicate under the shard write lock (so it must not re-enter the cache), fires on_evict after the lock is released, and requires no K: Clone bound.
ConcurrentCachePeek and ConcurrentCachePeekAsync: side-effect-free cache_peek / async_cache_peek (plus peek / async_peek aliases) for concurrent stores, with no recency promotion, no TTL refresh, no hit/miss metrics, and no lazy removal of expired entries. Implemented by the six sharded stores, which also expose an inherent peek(&self, &K) -> Option<V>. RedisCache, RedbCache, and AsyncRedisCache implement neither: peek is an in-memory concept, and for an IO-backed store there is no client-side state to skip while the operation remains a full round trip. Both traits are in the prelude.
ConcurrentCachedAsyncExt, a blanket extension trait over ConcurrentCachedAsync with ten async_-prefixed aliases (async_get, async_set, async_remove, async_remove_entry, async_delete, async_contains, async_clear, async_reset, async_get_or_set_with, async_try_get_or_set_with), mirroring ConcurrentCachedExt. In the prelude.
ConcurrentCached::cache_try_get_or_set_with and its async counterpart (both provided): fallible-init get-or-set returning Result<Result<V, E>, Self::Error>, store error outer, closure error inner; nothing is stored on a closure Err. ConcurrentCachedExt::try_get_or_set_with is the short alias. ConcurrentCached / ConcurrentCachedAsync also gained defaulted cache_get_or_set_with (get-then-set, non-atomic) and no-op-default cache_reset_metrics.
Metric and introspection parity: ConcurrentCacheBase gained cache_hits / cache_misses / cache_capacity / cache_evictions and a default metrics(), so a generic bound can read a sharded store's metrics; CachedExt gained capacity / evictions / reset; ConcurrentCachedExt gained len / is_empty / hits / misses / capacity / evictions / clear / reset; CachedPeek::peek, CloneCached::peek_with_expiry_status, and ConcurrentCloneCached::{get_with_expiry_status, peek_with_expiry_status} fill in the remaining aliases.
Cached::cache_contains (defaulted, get-based, overridden peek-based by the built-ins) and inherent contains on the six sharded stores, giving contains both spellings on both trait families. CachedExt::contains delegates to it, so contains no longer counts a hit/miss, promotes recency, or refreshes TTL, and reports expired entries as absent.
ExpiringLruCache::iter_order / key_order / value_order, completing LRU-family introspection parity, and TtlSortedCache::capacity() -> Option<usize>.
Runtime capacity resizing on the sharded LRU stores: set_max_size(&self, usize) -> Option<usize> and try_set_max_size(&self, usize) -> Result<Option<usize>, SetMaxSizeError>. Shrinking evicts LRU-excess entries per shard strictly by recency, fires on_evict, and counts evictions; resize is not atomic across shards. LruCache, LruTtlCache, and ExpiringLruCache gained the same pair (#180), and SetMaxSizeError (variants ZeroMaxSize and CapacityOverflow) replaces the mix of BuildError and std::io::Error the 2.x resize paths returned. CacheTtl::try_set_ttl is the matching strict TTL setter, returning SetTtlError::ZeroTtl.
per_shard_initial_capacity on the three unbounded sharded builders, the sharded counterpart of initial_capacity.
SerializeCached / SerializeCachedAsync with cache_set_ref / async_cache_set_ref, implemented by RedisCache / AsyncRedisCache / RedbCache, letting serialize-backed stores set an entry without taking ownership. #[concurrent_cached] calls the borrowed setter for any store implementing them, avoiding a value clone per set (#196, #195).
RedisCache / AsyncRedisCache implement cache_clear / async_cache_clear through a namespace-scoped SCAN + batched DEL (O(n), scoped to the cache's prefix, not a server flush), with glob metacharacters in the namespace/prefix escaped so they match literally (#200). RedisCache and AsyncRedisCache also implement Clone; RedbCache does not.
RedbCache::flush / async_flush force a durable commit, RedbCache::disk_path() returns the backing file path, and RedbCache::async_remove_expired_entries runs the sweep on the blocking thread pool so it is usable from async contexts.
RedisCacheError / RedbCacheError and their build-error siblings expose is_deserialization() -> bool, so callers can distinguish a codec failure from a storage or network error without a full match. Debug is implemented for RedisCache, AsyncRedisCache, and RedbCache, redacted to namespace/prefix/path/ttl/refresh.
PartialEq / Eq for ExpiringCache and ExpiringLruCache, and PartialEq / Eq / Hash for ConnectionString. NoEvict / HasEvict derive Clone, Copy, Debug, Default and are documented at the crate root.
Expires::expires_at(&self) -> Option<Instant> as a default method returning the value's expiry instant when tracked. Advisory only: is_expired() remains the authoritative liveness check, and existing impl Expires blocks get the default for free.
Macro attributes: force_refresh (a block expression over the arguments that bypasses the cached value, #146), in_impl = true for methods inside impl blocks including self receivers (#16, #140), companions_vis = "<vis>" to set the generated companions' visibility, companions = false to suppress the {fn}_no_cache / {fn}_prime_cache companions entirely, and ttl_millis (above). convert, create, force_refresh, map_error, and cache_prefix_block accept unquoted Rust in addition to the quoted-string form. map_error is optional on the disk and redis paths (the generated code uses .map_err(Into::into)?, so E: From<RedbCacheError> / From<RedisCacheError>). #[concurrent_cached] accepts result_fallback together with expires.
Macro ergonomics: #[cached] / #[concurrent_cached] accept reference arguments (&T, Option<&T>) on the default-key path, deriving an owned key without a convert (#202, #203); the crate root is resolved via proc-macro-crate, so a renamed or re-exported cached dependency works (#157); macro-introduced bindings are hygienically named __cached_*, so arguments named key, cache, or result no longer collide (#230, #114); and a generic function without key + convert produces a clear error (#80).
Compile-time missing-feature guards: #[cached] / #[once] / #[concurrent_cached] on an async fn without the async feature, a TTL attribute without time_stores, and #[concurrent_cached(disk = true)] / (redis = true) without redb_store / a redis feature all name the missing feature instead of surfacing errors from generated internals. A return type that does not implement Clone produces exactly one error, spanned at the return type.
#[doc(alias)] entries mapping the 2.x store names to their 3.0 types (SizedCache -> LruCache, TimedCache -> TtlCache, TimedSizedCache -> LruTtlCache) for docs.rs search.
The release workflow creates a git tag and GitHub release for each workspace crate that is newly published (#245), and refuses to publish a half-bumped workspace: bin/check-versions.sh fails the release when a cached_proc_macro* dependency pin disagrees with that subcrate's version, or when a stable cached would depend on a pre-release subcrate.

Security

sync_writes = "by_key" bucket selection seeds from a per-static RandomState instead of a fixed-seed hasher, so an attacker who knows the key space cannot collapse the lock buckets to force whole-cache serialization.
Corrupt or undecodable cached values on the redis/redb cache_get path self-heal by default: the entry is deleted and the call returns a miss so the cached function recomputes. Opt into fail-closed behavior with .strict_deserialization(true).
Redis credential handling is structural: resolve_connection_string() returns a redacting ConnectionString, the build path constructs sanitized synthetic errors (including the r2d2 pool-build failure and the NotUnicode env-var value, which is the connection string itself), and RedisCacheBuilder::connection_pool_connection_timeout bounds how long build waits for a connection. The legacy-JSON backward read requires the exact version field value, and client-side caching rejects a URL pinning RESP2 (which cannot deliver invalidation messages, so accepting it would silently serve stale data).
redb disk hardening on Unix: the cache directory is created 0700 and the database file forced to 0600 on every open (not only at creation); a symlink at the resolved db path or at a configured cache directory is rejected before opening; symlink and permission validation runs for the XDG default candidates, not only the temp fallback; and a read-only or group/world-writable candidate falls back to the temp directory.
RedbCacheError::CacheDeserialization / RedisCacheError::CacheDeserialization render their cached_value bytes as <N bytes redacted> in Debug, and are documented as potentially sensitive.

Fixed

{fn}_prime_cache no longer deadlocks or blocks readers: it ran the function body while holding the cache write lock, so a recursive prime re-locked the same static on the same thread (parking_lot is non-reentrant) and any prime blocked every reader for the full recompute. The body now runs before the lock is taken.
#[cached(result_fallback = true)] no longer overwrites a newer cached value with a stale one. The fallback was captured before the function body ran and written back unconditionally on Err, so a slow failing call could clobber a value a concurrent call had refreshed, and on a TTL store refresh its deadline. The fallback is now read under the same lock the write takes; result_fallback rejects a non-disabled sync_writes, so no caller could serialize the window themselves.
TTL expiry is anchored after the value factory resolves on every get-or-set path across TtlCache, LruTtlCache, and TtlSortedCache; several paths anchored before the factory, so a factory slower than the TTL produced an already-stale entry. Refreshing an entry under an overflowing TTL now clears the deadline, as a fresh insert already did.
Eviction accounting: the try-path get-or-set no longer fires on_evict or counts an eviction until the replacement factory succeeds; overwriting an expired entry fires on_evict and counts uniformly across the timed and sharded stores; a panicking on_evict during capacity eviction can no longer leave the cache over capacity; cache_clear_with_on_evict counts every removed entry rather than degrading to a silent cache_clear without a callback; and cache_remove samples expiry once, at removal, so a slow callback cannot turn a live entry into a None return.
Sweeps are panic-safe and two-phase (select, remove, count, then notify) across the in-memory and sharded stores. retain / evict previously fired on_evict inside the selection scan or removed entries eagerly while the user predicate ran, so a panicking predicate could remove nothing while having already run cleanup callbacks, or silently drop every entry already yielded. The sharded implementation records a Vec<bool> of decisions rather than cloned keys, so no K: Clone bound is added.
TtlSortedCache::set_and_get_mut no longer orphans a map row when the size trim it triggers unwinds: the stamp was unlinked from the deadline index and re-inserted after the trim, so a panic in between left the entry in the map but invisible to every index-driven sweep while still counted by cache_size(). TtlSortedCache::set_with(..).evict() also performs the expiry sweep when max_size is configured and the map is under the bound, where the opt-in was previously discarded, and build reserves with try_reserve so a capacity-overflowing max_size returns Err(BuildError) instead of aborting.
RedisCache::cache_clear / async_cache_clear decode SCAN replies as bytes rather than String. Redis keys are binary-safe, so a single non-UTF-8 key anywhere in the cache's scope aborted the clear permanently: the offending key was never removed, so every retry failed identically.
RedbCache::cache_set no longer returns a displaced value that had already expired, and RedbCacheBuilder::build() returns RedbCacheBuildError::Storage instead of panicking when the backing file is damaged. A truncated tail is the ordinary result of a full disk or a killed process, and the file is a disposable cache, so it must not take the application down. (This cannot help under panic = "abort".)
Read-then-write races closed on both IO stores: redb refresh-on-hit, expiry eviction, and remove_expired_entries re-read and re-check inside the write transaction, and use a single time snapshot for the scan and write passes; redb self-heal re-reads before deleting; and the redis self-heal delete is conditional through a Lua script comparing stored bytes, so a concurrent valid write racing the read is not discarded.
RedbCache default-directory resolution self-heals a pre-existing cache directory created with legacy permissions by an earlier version, which permanently failed the security validation. The chmod only succeeds for the owner, so an attacker-owned or symlinked directory still falls through to the next candidate.
Sharded expiry evaluation happens once, under the shard write lock: ShardedTtlCache, ShardedLruTtlCache, ShardedExpiringCache, and ShardedExpiringLruCache previously evaluated a displaced entry's expiry outside the lock or twice, so a value crossing the threshold in that window fired on_evict without counting the eviction or produced a wrong return value. deep_clone on the expiring sharded stores reads the hit/miss counters under the shard read lock, so cloned metrics match cloned entries.
LruCache::cache_reset uses a fallible allocation path (a grown max_size could request a HashMap capacity past the allocation limit and panic), and internal LRU list pre-allocation saturates instead of overflowing.
Macro correctness: the #[once] generic-value-type guard compares whole idents, so fn f<S: Into<String>>(..) -> String is no longer falsely rejected; a raw-identifier cache name (e.g. r#type) builds a working static instead of panicking; attributes written between the macro and the fn forward to every generated item, so #[cfg] gating stays in lockstep; user lint attributes reach the generated *_prime_cache companion; and no generated use places a name in a scope enclosing user code, so a user item named Cached or CloneCached is no longer shadowed.
Macro attribute errors span the offending attribute rather than the function name, and malformed key / convert / force_refresh values produce contextual errors explaining the expected syntax instead of a bare syn "unexpected token".
RedbCacheError, RedbCacheBuildError, RedisCacheError, and RedisCacheBuildError Display output includes the underlying cause, which was previously reachable only through Debug while the source type is documented as not public API.
ConcurrentCacheTtl::refresh_on_hit reflects the configured flag: the concurrent stores overrode only set_refresh_on_hit, so the getter always reported false through trait dispatch.
Cached for HashMap no longer requires S: Default, so HashMap<K, V, DefaultHashBuilder> implements Cached on wasm.
docs.rs feature annotations (doc(cfg)) on the async_core-gated impls and on AsyncRedisCacheBuilder::client_side_caching, which previously rendered as unconditionally available.

Changed

The in-memory and sharded stores are faster, with no contract change beyond the behavior changes listed above. The sharded stores resolve a read hit in one hash lookup instead of two, count evictions per shard rather than through a shared striped counter, and cache the host's CPU topology (sampled once per process in a OnceLock) instead of probing it on every construction. The LRU-family and expiry-aware stores sweep in one pass instead of collecting keys first, the TTL stores sample the clock once per operation instead of once per entry examined, and ExpiringCache is smaller per instance.
Sharded stores gained an inherent get_or_set_with returning V directly, so the common case needs no trait import or .unwrap().
#[must_use] is applied across the pure-query trait methods (cache_size / len / is_empty / metrics / hits / misses / ttl / refresh_on_hit / ...), the removal methods on the concurrent traits, CacheEvict::evict / ConcurrentCacheEvict::evict, CacheMetrics::hit_ratio, the order accessors, and the sharded builders. The short remove / remove_entry aliases and the inherent sharded set / remove are deliberately left un-annotated: on the inherent methods the attribute cannot fire on .unwrap() (which consumes the value) and would fire on correct fire-and-forget calls.
Return::set_was_cached is #[doc(hidden)] (macro plumbing); it remains pub and callable.
KeyedCache moved under a #[doc(hidden)] pub mod __private, so it no longer appears as a suggested import when a user references a removed legacy store name.
hashbrown updated to 0.17 (internal). Dev-only: criterion 0.8, googletest 0.14.
The published crate manifests no longer carry a [lints] table, so a future-toolchain warning firing in cached cannot break downstream builds, and specs/, local/, .cursorrules, and Makefile are excluded from the published package.

Documentation

The len / cache_size / iter / evict contract on lazy-eviction stores is documented in one place: len returns the stored count without an expiry scan (so it may include expired entries), iter omits expired entries from the view without removing them, and evict() reclaims them and yields an accurate live count.
The sharded inherent-vs-trait return-shape split is documented on all six sharded store types, including the UFCS disambiguation and the .unwrap() sharp edge.
The redis on-wire format (positional MessagePack array, REDIS_VALUE_VERSION) and the redb on-disk format (versioned file name, table name) are documented as stable for the 3.x series on the store struct docs; changes bump the embedded version and are reserved for a major release.
The Arc<T> return pattern for expensive-to-clone values is documented on the macros: the cache stores the Arc, and hits clone only the pointer (#64).
New runnable example examples/resilience.rs covering sync_writes = "by_key", result_fallback, and force_refresh, plus cache-invalidation (#21) and struct-method (#236) examples.

Open source →

cached_proc_macro_types

Release timeline

Releases

What's Changed

From the same repository

What's Changed

Breaking Changes

Minimum supported Rust version

Store renames and the disk backend (#237)

Trait surface

Store behavior

Builders

Error and metrics types

Macros

Features and runtime

Added

Security

Fixed

Changed

Documentation

What's Changed

What's Changed