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refactor(core): migrate lang_analyzer cache from bincode to postcard - #16
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Replace bincode 1.x (RUSTSEC-2025-0141 — permanently unmaintained) with postcard 1.x in the three call sites inside mlxcel-core's lang_analyzer/cache.rs. postcard 1.x is 1.0+ stable with a frozen wire format, serde-based (drop-in API), and is the embedded Rust ecosystem standard — a natural fit for an inference runtime crate. Changed files: Cargo.toml (bincode → postcard 1 alloc feature), cache.rs (bincode::deserialize → postcard::from_bytes, bincode::serialize → postcard::to_allocvec, doc comments updated), mod.rs (Bincode error variant → Postcard, module doc updated).
bincode 1.x is no longer in the dependency tree (replaced by postcard 1.x in mlxcel-core). Remove the ignore entry so cargo deny enforces the advisory going forward. The paste advisory (RUSTSEC-2024-0436) is retained — it is a separate transitive-via-tokenizers concern, unchanged by this PR.
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…ablup#16) Closes lablup#8. Migrates `mlxcel-core`'s `TokenLanguageIndex` on-disk cache off the unmaintained `bincode` 1.x (RUSTSEC-2025-0141 — project permanently ceased development) to `postcard` 1.x. ## Architectural choice — postcard - Drop-in serde-based API (`postcard::to_allocvec(&v)?` / `postcard::from_bytes::<T>(&bytes)?`) — minimal call-site change. - 1.0+ stable with frozen wire format — protects production users' cache compatibility across future dependency upgrades. - Embedded Rust ecosystem standard — natural fit for an inference-runtime cache. Alternatives considered: `bitcode` (faster but pre-1.0, wire-format changes between minors), `rkyv` (zero-copy over-engineering for a startup-time cache), `bincode` 2.x / 3.x (different maintainer team, name-confusion risk — Dependabot's auto-PR lablup#10 to bincode 3.x was explicitly closed in favor of this approach). ## Cache compatibility — graceful degradation `lang_analyzer/cache.rs` already has corrupt-detection: a deserialization failure renames the existing bincode-format file to `*.broken.<epoch>.bak` and rebuilds the cache from source. Users upgrading from a prior mlxcel release will trip this path automatically on the first cache read — no explicit migration code needed. ## Scope (3 files + Cargo.lock) - `src/lib/mlxcel-core/Cargo.toml` — `bincode = "1"` → `postcard = { version = "1", features = ["alloc"] }` - `src/lib/mlxcel-core/src/lang_analyzer/cache.rs` — 3 call sites + doc comments - `src/lib/mlxcel-core/src/lang_analyzer/mod.rs` — error variant `Bincode` → `Postcard` (no external match-arms on it, safe rename) - `deny.toml` — RUSTSEC-2025-0141 `[advisories.ignore]` entry removed (no longer applicable) Verified locally: `cargo deny check` clean (advisories ok, bans ok, licenses ok, sources ok); `cargo tree -p mlxcel-core -i bincode` returns "package not found" — bincode is fully removed from the dependency tree. Self-hosted clippy + test gate is queued behind the PR lablup#14 cold-build backlog at merge time; will run on main after the runner clears.
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Summary
bincode 1.x(RUSTSEC-2025-0141, permanently unmaintained) withpostcard 1.xinmlxcel-core'slang_analyzerdisk cache[advisories.ignore]entry fromdeny.tomlnow that bincode is gone from the dep treeArchitectural decision
postcard 1.xwas chosen over the other alternatives (bitcode,rkyv,bincode 2.x) for these reasons:bitcodeis pre-1.0 and has changed wire formats between minor versionspostcard::to_allocvec(&v)?/postcard::from_bytes::<T>(&bytes)?— minimal change to the 3 call sites in one fileCache format compatibility
mlxcel-core's corrupt-detection path in
lang_analyzer/cache.rsrenames any file that fails deserialization to*.broken.<epoch>.bakbefore rebuilding from the tokenizer source. Production users with old bincode-format caches will gracefully degrade on upgrade — the postcardfrom_bytescall will fail, the corrupt-detection path fires, and the cache is rebuilt automatically. No explicit migration code is needed.What changed
src/lib/mlxcel-core/Cargo.toml:bincode = "1"→postcard = { version = "1", features = ["alloc"] }src/lib/mlxcel-core/src/lang_analyzer/cache.rs:bincode::deserialize→postcard::from_bytes,bincode::serialize→postcard::to_allocvec, doc comments updatedsrc/lib/mlxcel-core/src/lang_analyzer/mod.rs:Bincode(#[from] bincode::Error)→Postcard(#[from] postcard::Error), module doc updateddeny.toml: removedRUSTSEC-2025-0141ignore entry; paste entry retainedVerification
cargo check --lib -p mlxcel-core --no-default-features— passes cleanlycargo tree -p mlxcel-core -i bincode— returns "package not found" (bincode fully removed)cargo deny check— passes withadvisories okand RUSTSEC-2025-0141 no longer ignoredCloses #8