fix: track CJS re-export import records to fix inline const and tree-shaking by h-a-n-a · Pull Request #8925 · rolldown/rolldown

h-a-n-a · 2026-03-26T16:53:51Z

Summary

When a CJS module conditionally re-exports from multiple sources (e.g., React's jsx-dev-runtime.js), the linker previously only followed the first import record. This could lead to incorrect inline const values and incomplete tree-shaking.

This PR:

Records which import records correspond to module.exports = require(...) during scanning, rather than relying on import_records.first()
Follows all CJS re-export targets when building resolved_exports
Tracks conflicting CJS exports when multiple targets provide the same name
Skips inline const for exports with CJS conflicts, since the runtime value depends on which branch executes
Uses the recorded import record indices to simplify the tree-shaking bailout heuristic

Background

// jsx-dev-runtime.js
if (process.env.NODE_ENV === 'production') {
  module.exports = require('./production');   // exports.jsxDEV = void 0
} else {
  module.exports = require('./development');  // exports.jsxDEV = function() {...}
}

Previously, add_exports_for_export_star used import_records.first() to find the re-export target. This meant only the first require() target's exports entered resolved_exports — the rest were silently dropped. This caused jsxDEV to be incorrectly inlined as void 0.

Related issues

Vite 8 regression: DevBundle crashes on TypeScript, chunk count increases, and DevTools build regresses vitejs/vite#21884 — the void 0 inlining case fixed by this PR
platform: "node" causes CJS module exports to be silently dropped (immer) #8345 (comment) — related discussion on the underlying issue
bundledDev: true replaces jsxDEV factory with (void 0) for JSX in conditional expressions vitejs/vite#21843 — related Vite issue, worked around by fix(bundled-dev): properly disable inlineConst optimization vitejs/vite#21865 (disabling inlineConst for affected packages). This PR fixes the root cause in rolldown so we can reenable inlineConst in Vite. cc @sapphi-red

Test plan

New inline_const_cjs_reexport - validates inline const works with multiple cjs re-exports
New tree_shaking/cjs_reexport_conditional — validates ESM+CJS mixed re-export (ESM first, CJS second)
just test-rust all green

h-a-n-a · 2026-03-26T16:54:06Z

fix: track CJS re-export import records to fix inline const and tree-shaking #8925 👈 (View in Graphite)
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Copilot

Pull request overview

Fixes incorrect export resolution for CommonJS “re-export” modules (module.exports = require(...)) in conditional patterns by tracking the specific import records involved, so the linker follows all possible re-export targets. This improves correctness for both inline-const and tree-shaking in mixed/conditional CJS re-export scenarios (e.g. React jsx-dev-runtime-style branching).

Changes:

Record the import record indices corresponding to module.exports = require(...) during AST scanning and persist them on EcmaView.
In link stage, follow all recorded CJS re-export targets when building resolved_exports, and track CJS export name conflicts to avoid unsafe inline-const.
Simplify the CJS tree-shaking bailout heuristic and add/extend integration tests + snapshots covering the regressions.

Reviewed changes

Copilot reviewed 30 out of 30 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
crates/rolldown_common/src/types/resolved_export.rs	Adds `cjs_conflicting_symbol_refs` to represent conditional CJS export name conflicts.
crates/rolldown_common/src/ecmascript/ecma_view.rs	Stores `cjs_reexport_import_record_ids` on `EcmaView` for downstream link/tree-shaking logic.
crates/rolldown/src/stages/link_stage/tree_shaking/include_statements.rs	Uses recorded re-export import record ids to decide when to bail out for conditional CJS re-exports.
crates/rolldown/src/stages/link_stage/bind_imports_and_exports.rs	Builds `resolved_exports` using recorded CJS re-export targets; records ambiguities/conflicts.
crates/rolldown/src/module_loader/runtime_module_task.rs	Initializes new `EcmaView` field for the runtime module.
crates/rolldown/src/module_finalizers/mod.rs	Skips inline-const when exports have recorded CJS conflicts.
crates/rolldown/src/ecmascript/ecma_module_view_factory.rs	Plumbs scanner output into `EcmaView` (re-export import record ids).
crates/rolldown/src/ast_scanner/mod.rs	Tracks `module.exports = require(...)` require spans and resolves them to import record indices post-scan.
crates/rolldown/src/ast_scanner/impl_visit.rs	Updates pattern match for `CommonJsAstType::Reexport` variant shape.
crates/rolldown/src/ast_scanner/cjs_export_analyzer.rs	Extends `Reexport` classification to carry the `require()` call span used for mapping to import records.
crates/rolldown/tests/rolldown/tree_shaking/cjs_reexport_conditional/reexporter.js	New conditional CJS re-export fixture (ESM vs CJS targets).
crates/rolldown/tests/rolldown/tree_shaking/cjs_reexport_conditional/main.js	New tree-shaking test entry importing a named export from the re-exporter.
crates/rolldown/tests/rolldown/tree_shaking/cjs_reexport_conditional/esm-impl.mjs	New ESM implementation branch fixture.
crates/rolldown/tests/rolldown/tree_shaking/cjs_reexport_conditional/cjs-impl.js	New CJS implementation branch fixture.
crates/rolldown/tests/rolldown/tree_shaking/cjs_reexport_conditional/artifacts.snap	Snapshot asserting both branches remain and exports are accessible.
crates/rolldown/tests/rolldown/tree_shaking/cjs_reexport_conditional/_test.mjs	Runtime assertion validating branch behavior under default env.
crates/rolldown/tests/rolldown/tree_shaking/cjs_reexport_conditional/_config.json	Enables treeshake for the new test case.
crates/rolldown/tests/rolldown/topics/hmr/inline_const_cjs_reexport/main.js	New HMR + inline-const regression fixture for jsx-dev-runtime-like conditional re-export.
crates/rolldown/tests/rolldown/topics/hmr/inline_const_cjs_reexport/jsx-dev-runtime.production.js	Production branch fixture exporting `void 0`.
crates/rolldown/tests/rolldown/topics/hmr/inline_const_cjs_reexport/jsx-dev-runtime.js	Conditional `module.exports = require(...)` re-exporter fixture.
crates/rolldown/tests/rolldown/topics/hmr/inline_const_cjs_reexport/jsx-dev-runtime.development.js	Development branch fixture exporting a function.
crates/rolldown/tests/rolldown/topics/hmr/inline_const_cjs_reexport/artifacts.snap	Snapshot ensuring `jsxDEV` is not incorrectly inlined to `void 0`.
crates/rolldown/tests/rolldown/topics/hmr/inline_const_cjs_reexport/_config.json	Enables devMode and inlineConst for the new HMR regression.
crates/rolldown/tests/rolldown/optimization/inline_const/cjs_reexport_first_import_record/reexporter.js	New regression: multiple requires, only one is the `module.exports = require(...)` target.
crates/rolldown/tests/rolldown/optimization/inline_const/cjs_reexport_first_import_record/real-exports.js	Fixture providing the actual export value.
crates/rolldown/tests/rolldown/optimization/inline_const/cjs_reexport_first_import_record/main.js	Entry importing named export from the re-exporter.
crates/rolldown/tests/rolldown/optimization/inline_const/cjs_reexport_first_import_record/debug.js	Fixture “decoy” require that should not be treated as the re-export target.
crates/rolldown/tests/rolldown/optimization/inline_const/cjs_reexport_first_import_record/artifacts.snap	Snapshot asserting inline-const selects the real export target, not the first import record.
crates/rolldown/tests/rolldown/optimization/inline_const/cjs_reexport_first_import_record/_test.mjs	Runtime assertion for the inline-const regression.
crates/rolldown/tests/rolldown/optimization/inline_const/cjs_reexport_first_import_record/_config.json	Enables inlineConst for the new optimization regression.

codspeed-hq · 2026-03-26T17:19:12Z

Merging this PR will not alter performance

✅ 4 untouched benchmarks
⏩ 10 skipped benchmarks¹

_{Comparing 03-27-fix_track_cjs_re-export_import_records_to_fix_inline_const_and_tree-shaking (724f077) with main (cffcd5e)²}

10 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩
No successful run was found on main (724f077) during the generation of this report, so cffcd5e was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

graphite-app · 2026-03-27T09:32:18Z

Merge activity

Mar 27, 9:32 AM UTC: h-a-n-a added this pull request to the Graphite merge queue.
Mar 27, 9:36 AM UTC: Merged by the Graphite merge queue.

@sapphi-red

…shaking (#8925) ## Summary When a CJS module conditionally re-exports from multiple sources (e.g., React's `jsx-dev-runtime.js`), the linker previously only followed the first import record. This could lead to incorrect inline const values and incomplete tree-shaking. This PR: - Records which import records correspond to `module.exports = require(...)` during scanning, rather than relying on `import_records.first()` - Follows all CJS re-export targets when building `resolved_exports` - Tracks conflicting CJS exports when multiple targets provide the same name - Skips inline const for exports with CJS conflicts, since the runtime value depends on which branch executes - Uses the recorded import record indices to simplify the tree-shaking bailout heuristic ## Background ```js // jsx-dev-runtime.js if (process.env.NODE_ENV === 'production') { module.exports = require('./production'); // exports.jsxDEV = void 0 } else { module.exports = require('./development'); // exports.jsxDEV = function() {...} } ``` Previously, `add_exports_for_export_star` used `import_records.first()` to find the re-export target. This meant only the first `require()` target's exports entered `resolved_exports` — the rest were silently dropped. This caused `jsxDEV` to be incorrectly inlined as `void 0`. ## Related issues - vitejs/vite#21884 — the `void 0` inlining case fixed by this PR - #8345 (comment) — related discussion on the underlying issue - vitejs/vite#21843 — related Vite issue, worked around by vitejs/vite#21865 (disabling `inlineConst` for affected packages). This PR fixes the root cause in rolldown so we can reenable `inlineConst` in Vite. cc @sapphi-red ## Test plan - [x] New `inline_const_cjs_reexport` - validates inline const works with multiple cjs re-exports - [x] New `tree_shaking/cjs_reexport_conditional` — validates ESM+CJS mixed re-export (ESM first, CJS second) - [x] `just test-rust` all green

@sapphi-red

## [1.0.0-rc.13] - 2026-04-01 ### 🚀 Features - add friendly error for unloadable virtual modules (#8955) by @sapphi-red - better error message for unsupported CSS error (#8911) by @sapphi-red ### 🐛 Bug Fixes - prevent chunk merging from leaking entry side effects (#8979) by @IWANABETHATGUY - correct inlining based on module's def format and esModule flag (#8975) by @h-a-n-a - generate init calls for excluded re-exports in strict execution order (#8858) by @IWANABETHATGUY - consistent order for `meta.chunks` in `renderChunk` hook (#8956) by @sapphi-red - subpath imports in glob imports failing to find files (#8885) by @kalvenschraut - browser: bundle binding types in dts output (#8930) by @nyan-left - ci: guard artifact download step in `vite-test-ubuntu` when build is skipped (#8934) by @Copilot - track CJS re-export import records to fix inline const and tree-shaking (#8925) by @h-a-n-a - use ImportKind::Import for common-chunk root computation (#8899) by @IWANABETHATGUY - watch: clear emitted_filenames between rebuilds (#8914) by @IWANABETHATGUY - ci: cache esbuild snapshots to avoid 429 rate limiting (#8921) by @IWANABETHATGUY - always check circular deps in chunk optimizer (#8915) by @IWANABETHATGUY - don't mark calls to reassigned bindings as pure (#8917) by @IWANABETHATGUY - magic-string: throw TypeError for non-string content args (#8905) by @IWANABETHATGUY - magic-string: add split-point validation and overwrite/update options (#8904) by @IWANABETHATGUY ### 🚜 Refactor - pre-compute has_side_effects on ChunkCandidate (#8981) by @IWANABETHATGUY - cleanup and simplify in dynamic_import.rs (#8927) by @ulrichstark - rename came_from_cjs to came_from_commonjs for consistency (#8938) by @IWANABETHATGUY - inline `create_ecma_view` return destructuring and remove redundant binding (#8932) by @shulaoda ### 📚 Documentation - document ensure_lazy_module_initialization_order in code-splitting design doc (#8931) by @IWANABETHATGUY ### 🧪 Testing - add regression test for runtime helper circular dependency (#8958) by @h-a-n-a - enable 8 previously-skipped MagicString remove tests (#8945) by @IWANABETHATGUY - add test for why PureAnnotation is needed in execution order check (#8933) by @IWANABETHATGUY ### ⚙️ Miscellaneous Tasks - add `@emnapi/runtime` and `@emnapi/core` as direct deps of `@rolldown/browser` (#8978) by @Copilot - deps: update dependency vite-plus to v0.1.15 (#8970) by @renovate[bot] - deps: update dependency oxfmt to ^0.43.0 (#8969) by @renovate[bot] - deps: upgrade oxc to 0.123.0 (#8967) by @shulaoda - justfile: deduplicate update-submodule as alias of setup-submodule (#8968) by @shulaoda - deps: update rollup submodule for tests to v4.60.1 (#8965) by @sapphi-red - deps: update test262 submodule for tests (#8966) by @sapphi-red - remove unused `type-check` scripts (#8957) by @sapphi-red - deps: update actions/cache action to v5 (#8953) by @renovate[bot] - deps: update npm packages to v6 (major) (#8954) by @renovate[bot] - deps: update npm packages (#8948) by @renovate[bot] - deps: update rust crates (#8949) by @renovate[bot] - deps: update github-actions (#8947) by @renovate[bot] - deps: update napi (#8943) by @renovate[bot] - deps: update dependency rolldown-plugin-dts to ^0.23.0 (#8944) by @renovate[bot] - regenerate testing snapshots (#8928) by @ulrichstark - deps: update dependency rust to v1.94.1 (#8923) by @renovate[bot] ### ❤️ New Contributors * @kalvenschraut made their first contribution in [#8885](#8885) * @nyan-left made their first contribution in [#8930](#8930) Co-authored-by: shulaoda <165626830+shulaoda@users.noreply.github.com>

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fix(bundled-dev): properly disable inlineConst optimization vitejs/vite#21865

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release: v1.0.0-rc.13 #8971

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fix: track CJS re-export import records to fix inline const and tree-shaking#8925

fix: track CJS re-export import records to fix inline const and tree-shaking#8925
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Merging this PR will not alter performance

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