fix(dev/lazy): avoid module reinitialization in lazy compilation patches by h-a-n-a · Pull Request #9179 · rolldown/rolldown

h-a-n-a · 2026-04-21T07:32:02Z

Summary

When a module appears in two lazy-compilation chunks served concurrently
(e.g. two compileLazyEntry requests racing for shared.js), the browser
runs the module body twice. Non-idempotent module code blows up — concretely,
Object.defineProperty(this, "key", { configurable: false }) on the second
run throws Cannot redefine property.

This PR makes module initializers opt into runtime-side deduping:

createEsmInitializer / createCjsInitializer take a new dedup flag.
When truthy and the stable id is already in runtime.modules, the factory
is skipped (or, for CJS, the registered exports are reused).
The Rust emitter (HmrAstFinalizer) gains a dedup_module_initializer
field. compile_lazy_entry sets it to true; the two HMR-patch render
paths set it to false so HMR keeps re-running the factory and replacing
exports — that's the whole point of a patch.
The stable module id is now passed into the factory as
__rolldown_module_id__, so registerModule and createModuleHotContext
reference it by identifier instead of duplicating the string literal.
The lazy proxy template deletes its own runtime.modules entry before
triggering the real chunk, so the dedup gate on the real module's id
starts from a clean slate.

The dedup gate is a workaround. The proper fix is a runtime API for module
disposal that HMR can call before re-execution; see the TODO on
HmrAstFinalizer::dedup_module_initializer.

Test plan

cargo test -p rolldown --test integration (1690 passed, 70 ignored)
cargo clippy -p rolldown --tests --no-deps clean

h-a-n-a · 2026-04-21T07:32:16Z

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commit: 01b0ad7

codspeed-hq · 2026-04-27T07:39:23Z

Merging this PR will not alter performance

✅ 4 untouched benchmarks
⏩ 10 skipped benchmarks¹

_{Comparing 04-21-fix_fix_race_condition_of_module_initialization_in_hmr_patches (27026df) with main (5a5f8f5)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 (27026df) during the generation of this report, so 5a5f8f5 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

graphite-app · 2026-04-27T08:09:02Z

Merge activity

Apr 27, 8:09 AM UTC: h-a-n-a added this pull request to the Graphite merge queue.
Apr 27, 8:15 AM UTC: Merged by the Graphite merge queue.

…hes (#9179) ## Summary When a module appears in two lazy-compilation chunks served concurrently (e.g. two `compileLazyEntry` requests racing for `shared.js`), the browser runs the module body twice. Non-idempotent module code blows up — concretely, `Object.defineProperty(this, "key", { configurable: false })` on the second run throws `Cannot redefine property`. This PR makes module initializers opt into runtime-side deduping: - `createEsmInitializer` / `createCjsInitializer` take a new `dedup` flag. When truthy and the stable id is already in `runtime.modules`, the factory is skipped (or, for CJS, the registered exports are reused). - The Rust emitter (`HmrAstFinalizer`) gains a `dedup_module_initializer` field. `compile_lazy_entry` sets it to `true`; the two HMR-patch render paths set it to `false` so HMR keeps re-running the factory and replacing exports — that's the whole point of a patch. - The stable module id is now passed into the factory as `__rolldown_module_id__`, so `registerModule` and `createModuleHotContext` reference it by identifier instead of duplicating the string literal. - The lazy proxy template deletes its own `runtime.modules` entry before triggering the real chunk, so the dedup gate on the real module's id starts from a clean slate. The dedup gate is a workaround. The proper fix is a runtime API for module disposal that HMR can call before re-execution; see the TODO on `HmrAstFinalizer::dedup_module_initializer`. ## Test plan - [x] `cargo test -p rolldown --test integration` (1690 passed, 70 ignored) - [x] `cargo clippy -p rolldown --tests --no-deps` clean

@IWANABETHATGUY

## [1.0.0-rc.18] - 2026-04-29 ### 💥 BREAKING CHANGES - optimization: default unspecified inlineConst.mode to smart (#9248) by @IWANABETHATGUY ### 🐛 Bug Fixes - rolldown_plugin_vite_import_glob: return error instead of panicking when virtual module uses a relative glob (#9241) by @shulaoda - binding: treat empty inlineConst object as omitted (#9247) by @IWANABETHATGUY - rolldown: keep enum declaration for optional-chain access (#9229) by @Dunqing - link_stage: restore inline let-else in exports-kind filter (#9237) by @IWANABETHATGUY - dev/lazy: avoid module reinitialization in lazy compilation patches (#9179) by @h-a-n-a - dev: visit identifier references for runtime rewrites in HMR finalizer (#9191) by @h-a-n-a - chunk-optimizer: pick dominator for runtime placement to avoid cycles (#9164) by @IWANABETHATGUY - make `this.emitFile` chunk path synchronous to avoid deadlock (#9031) by @lazarv - use sentinel id for `browser: false` ignored modules (#9192) by @shulaoda - prevent chunk optimizer from creating import cycles (#9228) by @IWANABETHATGUY ### 🚜 Refactor - replace tokio::sync::Mutex with std::sync::Mutex for non-IO data (#9176) by @shulaoda - rolldown_plugin_vite_import_glob: do not rewrite import path for absolute base (#9195) by @shulaoda - runtime_helper: wrap DependedRuntimeHelperMap in a struct (#9215) by @IWANABETHATGUY - drop redundant clear() in determine_safely_merge_cjs_ns (#9206) by @IWANABETHATGUY - clean up generate_lazy_export (#9208) by @IWANABETHATGUY - bitset: return bool from set_bit to fuse guard-and-set (#9207) by @IWANABETHATGUY - link_stage: simplify exports-kind filter and clarify safety comments (#9205) by @IWANABETHATGUY ### 📚 Documentation - determine_module_exports_kind (#9252) by @IWANABETHATGUY - fix dead link to esbuild ESM/CJS interop tests (#9230) by @Copilot - remove CSS bundling references (#9234) by @shulaoda - correct IncrementalFullBuild row in BundleMode table (#9214) by @IWANABETHATGUY - design: add bundler data lifecycle design doc (#9212) by @hyf0 - remove minifier alpha status notices (#9202) by @sapphi-red ### ⚙️ Miscellaneous Tasks - upgrade oxc to 0.128.0 (#9260) by @shulaoda - deps: bump rolldown-ariadne to 0.6.0 (#9254) by @IWANABETHATGUY - deps: update github actions (#9259) by @renovate[bot] - deps: update github actions (#9258) by @renovate[bot] - remove renovate overrides (#9257) by @Boshen - use ubuntu-latest for security workflow (#9256) by @Boshen - notify Discord around release publish (#9251) by @Boshen - add release environment to npm publish workflow (#9250) by @Boshen - justfile: drop the `--` separator before forwarded args in `vp run` (#9246) by @shulaoda - deps: update test262 submodule for tests (#9243) by @sapphi-red - add more tracing instrumentations (#9220) by @sapphi-red - rolldown_plugin_vite_import_glob: remove outdated sourcemap doc comment (#9213) by @shulaoda - update security workflow (#9201) by @Boshen ### ❤️ New Contributors * @lazarv made their first contribution in [#9031](#9031) Co-authored-by: shulaoda <165626830+shulaoda@users.noreply.github.com>

github-actions Bot assigned h-a-n-a Apr 21, 2026

This was referenced Apr 21, 2026

fix(rolldown_plugin_lazy_compilation): use loadExports for fetched proxy to preserve original export names #9132

Draft

fix: collect destructured bindings in HMR module exports #9146

Merged

h-a-n-a force-pushed the 04-21-fix_fix_race_condition_of_module_initialization_in_hmr_patches branch 2 times, most recently from ff3c657 to d2c0b1d Compare April 21, 2026 10:25

h-a-n-a force-pushed the 04-16-fix_rolldown_plugin_lazy_compilation_use_loadexports_for_fetched_proxy_to_preserve_original_export_names branch from 7487a99 to 496f339 Compare April 21, 2026 10:25

h-a-n-a force-pushed the 04-21-fix_fix_race_condition_of_module_initialization_in_hmr_patches branch from d2c0b1d to 01b0ad7 Compare April 21, 2026 10:27

h-a-n-a added the trigger: preview label Apr 21, 2026

h-a-n-a mentioned this pull request Apr 22, 2026

fix(dev): visit identifier references for runtime rewrites in HMR finalizer #9191

Merged

h-a-n-a changed the title ~~fix: fix race condition of module initialization in HMR patches~~ fix: avoid module reinitialization in lazy compilation patches Apr 23, 2026

h-a-n-a force-pushed the 04-21-fix_fix_race_condition_of_module_initialization_in_hmr_patches branch from 01b0ad7 to 43390b3 Compare April 27, 2026 07:05

h-a-n-a changed the base branch from 04-16-fix_rolldown_plugin_lazy_compilation_use_loadexports_for_fetched_proxy_to_preserve_original_export_names to graphite-base/9179 April 27, 2026 07:29

h-a-n-a force-pushed the 04-21-fix_fix_race_condition_of_module_initialization_in_hmr_patches branch from 43390b3 to f3c3c87 Compare April 27, 2026 07:29

h-a-n-a force-pushed the graphite-base/9179 branch from 496f339 to 7f39bc5 Compare April 27, 2026 07:29

h-a-n-a changed the base branch from graphite-base/9179 to 04-21-fix_visit_identifier_references_for_runtime_rewrites_in_hmr_finalizer April 27, 2026 07:30

h-a-n-a changed the title ~~fix: avoid module reinitialization in lazy compilation patches~~ fix(dev/lazy): avoid module reinitialization in lazy compilation patches Apr 27, 2026

h-a-n-a marked this pull request as ready for review April 27, 2026 07:33

h-a-n-a requested a review from sapphi-red April 27, 2026 07:40

h-a-n-a changed the base branch from 04-21-fix_visit_identifier_references_for_runtime_rewrites_in_hmr_finalizer to graphite-base/9179 April 27, 2026 07:40

h-a-n-a force-pushed the graphite-base/9179 branch from 7f39bc5 to b8fc6ba Compare April 27, 2026 07:43

h-a-n-a force-pushed the 04-21-fix_fix_race_condition_of_module_initialization_in_hmr_patches branch from f3c3c87 to b4dc062 Compare April 27, 2026 07:43

h-a-n-a changed the base branch from graphite-base/9179 to 04-21-fix_visit_identifier_references_for_runtime_rewrites_in_hmr_finalizer April 27, 2026 07:43

h-a-n-a force-pushed the 04-21-fix_fix_race_condition_of_module_initialization_in_hmr_patches branch from b4dc062 to 90d94c1 Compare April 27, 2026 07:45

sapphi-red approved these changes Apr 27, 2026

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graphite-app Bot force-pushed the 04-21-fix_visit_identifier_references_for_runtime_rewrites_in_hmr_finalizer branch from b8fc6ba to 0689e35 Compare April 27, 2026 08:09

graphite-app Bot force-pushed the 04-21-fix_fix_race_condition_of_module_initialization_in_hmr_patches branch from 90d94c1 to 27026df Compare April 27, 2026 08:10

Base automatically changed from 04-21-fix_visit_identifier_references_for_runtime_rewrites_in_hmr_finalizer to main April 27, 2026 08:14

graphite-app Bot merged commit 27026df into main Apr 27, 2026
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graphite-app Bot deleted the 04-21-fix_fix_race_condition_of_module_initialization_in_hmr_patches branch April 27, 2026 08:15

h-a-n-a mentioned this pull request Apr 28, 2026

fix(dev/lazy): fix exports of lazy requests in lazy chunks #9249

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rolldown-guard Bot mentioned this pull request Apr 29, 2026

release: v1.0.0-rc.18 #9255

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h-a-n-a mentioned this pull request Apr 29, 2026

fix(dev): apply __toCommonJS interop when CJS requires ESM in HMR finalizer #9261

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rolldown-guard Bot mentioned this pull request Apr 29, 2026

release: v1.0.0-rc.18 #9266

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rolldown-guard Bot mentioned this pull request Apr 29, 2026

release: v1.0.0-rc.19 #9268

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fix(dev/lazy): avoid module reinitialization in lazy compilation patches#9179

fix(dev/lazy): avoid module reinitialization in lazy compilation patches#9179
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