fix(esm-library): deconflict module external helper names

[JSerFeng]

Summary

This PR fixes modern-module ESM rendering when a ModuleExternal init fragment introduces top-level bindings that collide with source bindings during deconfliction.

It also adds an externals case that covers helper-shaped source code directly in index.js, including a literal require("fs"), while the project external for fs is also configured as node-commonjs.

Root Cause

rspack_plugin_esm_library previously reserved namespace-import locals from ModuleExternal init fragments, but it did not reserve other top-level declarations introduced by those fragments. That allowed generated helpers like __rspack_createRequire and __rspack_createRequire_require to collide with user/source bindings in ESM library rendering.

What Changed

• reserve top-level declarations from ModuleExternal init fragments before top-level symbol deconfliction
• keep the reservation order aligned with init-fragment render order and key deduplication semantics
• add unit coverage for helper/provided-dependency declarations in link.rs
• add an ESM output case where the source already contains helper-shaped bindings and require("fs"), while fs is also a node-commonjs external

Validation

• cargo test -p rspack_plugin_esm_library link --lib
• cargo fmt --all --check
• cd tests/rspack-test && PATH="/tmp/codex-bin:$HOME/.nvm/versions/node/v20.19.0/bin:$PATH" pnpm testu EsmOutput.test.js -t "externals/node-commonjs-helper-name-collision"
• cd tests/rspack-test && PATH="/tmp/codex-bin:$HOME/.nvm/versions/node/v20.19.0/bin:$PATH" pnpm test EsmOutput.test.js -t "externals/node-commonjs-helper-name-collision"

[codspeed-hq]

Merging this PR will degrade performance by 4.12%

⚡ 2 improved benchmarks
❌ 2 regressed benchmarks
✅ 24 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	rust@create_module_hashes	21.7 ms	21.4 ms	+1.42%
❌	Simulation	rust@persistent_cache_restore_after_single_file_change@basic-react-development	27.8 ms	29 ms	-4.12%
⚡	Simulation	rust@persistent_cache_restore@basic-react-development	26.8 ms	26.1 ms	+2.74%
❌	Simulation	rust@create_chunk_ids	10.2 ms	10.6 ms	-3.39%

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_{Comparing JSerFeng:fy/fix-esm-library-module-external-name-collision (2394a16) with main (e26bca5)}

[JSerFeng]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Hooray!

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[JSerFeng]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Keep it up!

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[Copilot]

Pull request overview

Fixes ESM-library rendering deconfliction when ModuleExternal init fragments introduce helper bindings that can collide with source/module top-level bindings (notably the node-commonjs createRequire helper).

Changes:

• Collect and reserve top-level declarations introduced by ModuleExternal init fragments prior to top-level symbol deconfliction.
• Refactor module-external init-fragment collection to keep reservation behavior aligned with init-fragment render ordering and key de-duplication.
• Add unit tests for the new reservation behavior and add an ESM output test case covering helper-shaped source bindings plus node-commonjs externals.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
crates/rspack_plugin_esm_library/src/link.rs	Reserves additional top-level decls from ModuleExternal init fragments and adds unit coverage for the new parsing/reservation logic.
tests/rspack-test/esmOutputCases/externals/node-commonjs-helper-name-collision/rspack.config.js	Adds a repro config that externalizes fs as node-commonjs.
tests/rspack-test/esmOutputCases/externals/node-commonjs-helper-name-collision/index.js	Adds a repro entry asserting helper-name deconfliction against source bindings and require("fs").
tests/rspack-test/esmOutputCases/externals/node-commonjs-helper-name-collision/__snapshots__/esm.snap.txt	Snapshot verifying generated ESM output uses deconflicted helper names.

---

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[JSerFeng]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Bravo.

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[github-actions]

📝 Rspack Ecosystem CI: Open

suite	result
rstest	❌ failure
modernjs	✅ success
lynx-stack	❌ failure
rsbuild	✅ success
rspress	✅ success
rsbuild-rsc-plugin	✅ success
rsdoctor	✅ success
rslib	❌ failure
examples	❌ failure
devserver	✅ success
plugin	❌ failure