perf(loader): dispatch parallel loaders from Rust

[intellild]

Summary

• Dispatch parallel JavaScript loader tasks directly from the Rust loader runner through a generic unbounded MPMC worker queue.
• Keep persistent JavaScript workers independent from loader-specific registration: each worker receives one native task, executes it, completes it, then calls recv again.
• Expose loader context and the canonical NormalModule through native-backed accessors so parallel execution does not copy the module or bulk context state through the JavaScript main thread.
• Keep Rule.use.options in a compiler-owned map on the JavaScript main thread. Native code carries only a u32 handle; a worker requests the value over its existing MessagePort, ordinary values use structured clone, and functions continue to use the synchronous SharedArrayBuffer + Atomics bridge.

Execution flow:

Rust loader runner
  enqueue native task
       ↓
generic unbounded MPMC queue
       ↓
persistent JS worker recv loop
       ↓
native-backed loader context accessors
       ↓
run pitch/normal loader and complete native task

Loader options flow:

Rule.use.options
  stored in main-isolate compiler map
       ↓ u32 handle only
Rust loader metadata / worker task
       ↓
worker requests handle over MessagePort
       ↓
structured clone ordinary values
function handles synchronously call the main isolate

For example, a Babel loader cache hit no longer requires the main JavaScript thread to materialize and forward the parallel loader payload or serialize the options object through V8. A non-parallel loader still receives the original options object identity, while a parallel loader receives a worker-local structured clone with Map, typed arrays, URLs, and function options preserved by the bridge.

Related links

• Follow-up implementation plan is included in task.md.

Checklist

• Tests updated.
• Documentation updated.

Validation:

• cargo check -p rspack_binding_api -p rspack_core -p rspack_loader_runner -p rspack
• cargo test -p rspack --test loader --no-run
• pnpm run build:binding:dev
• pnpm run build:js
• pnpm exec rs check --type-check
• pnpm run test -t "configCases/loader-parallel" (62 tests passed)

---

by OpenAI Codex

[github-actions]

📦 Binary Size-limit

Comparing 70c6e24 to refactor(core): remove BuildInfo clone (#15377) by hardfist

❌ Size increased by 84.13KB from 68.24MB to 68.32MB (⬆️0.12%)

[github-actions]

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