feat: EsmLibraryPlugin supports preserveModules

[JSerFeng]

Summary

Preserve_modules now supported by splitting specific modules into single chunk

• Use optimizeChunks hook to split, not using splitChunks because it's performance is not expected

Make them export their symbols, main changes is in add_chunk_export, it can now export local to different names

For add_chunk_export(local, exported_name, strict)

if local is already exported
- if strict: error
- if not strict: use already exported name

if local is not exported
- if exported name is already exported and strict: error
- if exported name is already exported and not strict: find new name to export
- if exported name is not exported, export with that name

Related links

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Copilot]

Pull Request Overview

Add preserveModules support to EsmLibraryPlugin, enabling splitting specified modules into individual chunks and ensuring their exports are surfaced correctly.

• Add EsmLibraryPlugin option preserveModules (path), wire through Node bindings, and implement chunk splitting in Rust
• Update ESM linking/rendering to ensure proper export symbol handling and deterministic namespace emission
• Extend test tools to configure plugin options; add new tests and snapshots for preserve-modules; clean up snapshot runtimes

Reviewed Changes

Copilot reviewed 32 out of 33 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/rspack-test/esmOutputCases/re-exports/re-export-external/snapshots/esm.snap.txt	Snapshot cleanup (remove empty runtime).
tests/rspack-test/esmOutputCases/re-exports/deep-re-exports-esm/snapshots/esm.snap.txt	Snapshot cleanup (remove empty runtime).
tests/rspack-test/esmOutputCases/preserve-modules/conflict-symbol/test.config.js	Add test config with preserveModules path.
tests/rspack-test/esmOutputCases/preserve-modules/conflict-symbol/src/index.js	Test for preserved modules and strict export symbols.
tests/rspack-test/esmOutputCases/preserve-modules/conflict-symbol/src/demo/other.js	Additional test module for conflict case.
tests/rspack-test/esmOutputCases/preserve-modules/conflict-symbol/src/demo/index.js	Additional test module for conflict case.
tests/rspack-test/esmOutputCases/preserve-modules/conflict-symbol/rspack.config.js	Rspack config for conflict test.
tests/rspack-test/esmOutputCases/preserve-modules/conflict-symbol/snapshots/esm.snap.txt	Snapshot for conflict-symbol preserve-modules.
tests/rspack-test/esmOutputCases/preserve-modules/basic/test.config.js	Add test config with preserveModules path.
tests/rspack-test/esmOutputCases/preserve-modules/basic/src/index.js	Basic preserve-modules test entry.
tests/rspack-test/esmOutputCases/preserve-modules/basic/src/demo/index.js	Basic preserve-modules demo module.
tests/rspack-test/esmOutputCases/preserve-modules/basic/rspack.config.js	Rspack config for basic preserve-modules.
tests/rspack-test/esmOutputCases/preserve-modules/basic/other2/index.js	Ancillary module for basic test.
tests/rspack-test/esmOutputCases/preserve-modules/basic/other1/index.js	Ancillary module for basic test.
tests/rspack-test/esmOutputCases/preserve-modules/basic/snapshots/esm.snap.txt	Snapshot for basic preserve-modules.
tests/rspack-test/esmOutputCases/externals/externals-import-render/snapshots/esm.snap.txt	Snapshot cleanup (remove empty runtime).
tests/rspack-test/esmOutputCases/dynamic-import/import-self/snapshots/esm.snap.txt	Snapshot cleanup (remove empty runtime).
tests/rspack-test/esmOutputCases/deconflict/other-chunk-local/snapshots/esm.snap.txt	Snapshot cleanup (remove empty runtime).
tests/rspack-test/esmOutputCases/deconflict/deconflit-local/snapshots/esm.snap.txt	Snapshot cleanup (remove empty runtime).
packages/rspack/src/builtin-plugin/EsmLibraryPlugin.ts	Add options to plugin and forward to builtin.
packages/rspack/etc/core.api.md	Update API docs for EsmLibraryPlugin options.
packages/rspack-test-tools/src/type.ts	Add esmLibPluginOptions to test config type.
packages/rspack-test-tools/src/case/esm-output.ts	Inject EsmLibraryPlugin options into tests; adjust bundle discovery.
packages/rspack-test-tools/etc/test-tools.api.md	Update public test-tools API docs.
crates/rspack_plugin_esm_library/src/render.rs	Mark runtime chunks; deterministic namespace order; restructure add() emission.
crates/rspack_plugin_esm_library/src/preserve_modules.rs	Implement module splitting and entry wiring for preserveModules.
crates/rspack_plugin_esm_library/src/plugin.rs	Wire preserveModules option; remove empty runtimes; hook optimize_chunks.
crates/rspack_plugin_esm_library/src/link.rs	Improve export symbol management; link for preserved modules; various fixes.
crates/rspack_plugin_esm_library/src/lib.rs	Register preserve_modules module.
crates/rspack_plugin_esm_library/src/chunk_link.rs	Change exports set to ordered set.
crates/rspack_binding_api/src/raw_options/raw_builtins/raw_esm_lib.rs	Define RawEsmLibraryPlugin for Node binding.
crates/rspack_binding_api/src/raw_options/raw_builtins/mod.rs	Hook up RawEsmLibraryPlugin to EsmLibraryPlugin constructor.

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[github-actions]

📦 Binary Size-limit

Comparing c7bd199 to test: display error location in jsdom (#11937) by harpsealjs

❌ Size increased by 50.75KB from 47.73MB to 47.78MB (⬆️0.10%)

[codspeed-hq]

CodSpeed Performance Report

Merging #11921 will not alter performance

_{Comparing esm-lib-plugin (c7bd199) with main (126822e)}

Summary

✅ 17 untouched