turbopack: gate ValueDebugFormat and ValueDebug behind debug_assertions#92628
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turbopack: gate ValueDebugFormat and ValueDebug behind debug_assertions#92628
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The ValueDebugFormat trait method, ValueDebugFormatString enum, and all related impl blocks (for Vc, ResolvedVc, ReadRef, MappedReadRef, AliasMap, and all std/auto_hash_map/smallvec/FxIndex* types) are now compiled only in debug builds. In release builds the derive macros emit empty ValueDebugFormat impls (no method) and lightweight ValueDebug impls that return the type name only, eliminating ~2.1% of binary size from the formatting machinery. Co-Authored-By: Claude <noreply@anthropic.com>
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sokra
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Apr 11, 2026
sokra
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Apr 11, 2026
sokra
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Apr 11, 2026
sokra
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Apr 11, 2026
Instead of emitting a lightweight no-op ValueDebug impl for each type in release builds, replace the value_trait definition itself with an empty marker trait + blanket impl in release builds. This means no per-type ValueDebug registration code is generated at all in release builds. Co-Authored-By: Claude <noreply@anthropic.com>
lukesandberg
approved these changes
Apr 13, 2026
- Move all `#[cfg(debug_assertions)]`-gated items into a single `detail` module so the gate is declared once instead of on every item - Use `futures::future::BoxFuture` for the `Async` variant of `ValueDebugFormatString` instead of the verbose inline type Co-Authored-By: Claude <noreply@anthropic.com>
This was referenced Apr 23, 2026
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What?
Gate
ValueDebugFormatandValueDebugbehind#[cfg(debug_assertions)]across the turbopack crates, eliminating all debug formatting machinery from release binaries entirely.Why?
ValueDebugFormatandValueDebugcontribute to release binary bloat. The field-level formatting logic (iterating struct fields, resolvingVcs, formatting collections recursively) and the per-typeValueDebugtrait registrations are purely debugging aids with no value in production binaries.Measured impact: -7.3 MiB (-5.5%) reduction in release
libnext_napi_bindings.sobinary size (from 126.26 MiB to 119.31 MiB).How?
ValueDebugtrait (debug/mod.rs):#[turbo_tasks::value_trait(no_debug)]withdbg()/dbg_depth()methods,ValueDebugFormatString, all blanket impls for collections/tuples/etc.impl<T: ?Sized> ValueDebug for T {}. This satisfies the supertrait bound on all value traits at zero cost — no per-type impl code is generated.ValueDebugFormattrait (debug/mod.rs):value_debug_formatmethod only exists under#[cfg(debug_assertions)]. In release builds, the trait is still present (for derive macros to reference) but has no methods.String,RcStr,Option,Vec,SmallVec,AutoSet,AutoMap,HashMap,FxIndexSet,FxIndexMap, tuples) are gated behinddebug_assertions.ValueDebugFormatString,PassthroughDebug,vdbg,internalsubmodule,value_debug_format_field) is compiled away.Proc-macros:
#[derive(ValueDebugFormat)]: emits a full impl withvalue_debug_formatmethod in debug builds, empty impl in release builds.#[derive(ValueDebug)]andvalue_implblocks: emit full debug impl in debug builds only — no release impl at all (the blanket marker trait impl covers it).#[turbo_tasks::value]: transparent types get#[cfg(debug_assertions)]on the manualValueDebugimpl. Non-transparent types use#[cfg_attr(debug_assertions, derive(turbo_tasks::debug::internal::ValueDebug))]so theinternalmodule is never referenced in release.#[turbo_tasks::value_trait]: theDynamic/Upcast/UpcastStrictimpls forBox<dyn ValueDebug>are gated behind#[cfg(debug_assertions)].Callers (
vc/mod.rs,vc/resolved.rs,read_ref.rs,mapped_read_ref.rs,macro_helpers.rs,alias_map.rs):impl ValueDebugFormatblocks and their imports are gated behind#[cfg(debug_assertions)].Verification
cargo check --release— clean (no errors, no warnings)cargo clippy --all-targets— clean