feat(dev/lazy): support dynamic `import(..)` by hyf0 · Pull Request #7726 · rolldown/rolldown

hyf0 · 2025-12-31T18:25:01Z

Same as #7609 but use stable module id instead of module id.

hyf0 · 2025-12-31T18:25:18Z

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Copilot

Pull request overview

This PR implements lazy compilation for dynamic imports in development mode, allowing modules imported via import() to be compiled on-demand rather than at build time. This optimization aims to improve development cold start times.

Key changes:

Adds lazy compilation plugin that creates proxy modules for dynamic imports
Implements /lazy HTTP endpoint to serve on-demand compiled modules
Integrates lazy compilation state tracking into DevEngine and bundle coordinator
Adds runtime support for client ID management and proxy module unwrapping

Reviewed changes

Copilot reviewed 37 out of 38 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
`crates/rolldown_plugin_lazy_compilation/`	Core plugin implementing lazy compilation with proxy modules and state tracking
`crates/rolldown_dev/src/dev_engine.rs`	Adds `compile_lazy_entry` method and module change notifications
`crates/rolldown_dev/src/bundle_coordinator.rs`	Handles programmatic module changes to trigger rebuilds
`packages/test-dev-server/src/dev-server.ts`	Implements `/lazy` endpoint and client ID management
`crates/rolldown/src/hmr/hmr_stage.rs`	Adds lazy entry compilation with partial scan support
`crates/rolldown/src/hmr/hmr_ast_finalizer.rs`	Supports computed property syntax for non-identifier exports
`examples/lazy/`	Example demonstrating lazy compilation feature
`pnpm-lock.yaml`	Lock file updates for new example dependencies

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packages/test-dev-server/src/dev-server.ts

crates/rolldown_plugin_lazy_compilation/src/lazy_compilation_plugin.rs

packages/test-dev-server/src/dev-server.ts

github-actions · 2026-01-01T21:01:11Z

Benchmarks Rust

target: main(77768f5)
pr: hyf_lazy_new(93766ca)

group                                                        pr                                     target
-----                                                        --                                     ------
bundle/bundle@multi-duplicated-top-level-symbol              1.00     63.3±2.58ms        ? ?/sec    1.07     67.7±1.56ms        ? ?/sec
bundle/bundle@multi-duplicated-top-level-symbol-sourcemap    1.00     69.4±1.89ms        ? ?/sec    1.10     76.2±1.35ms        ? ?/sec
bundle/bundle@rome_ts                                        1.00    106.4±3.03ms        ? ?/sec    1.01    107.0±2.47ms        ? ?/sec
bundle/bundle@rome_ts-sourcemap                              1.00    118.3±1.58ms        ? ?/sec    1.02    121.2±2.36ms        ? ?/sec
bundle/bundle@threejs                                        1.00     39.2±1.31ms        ? ?/sec    1.01     39.5±1.97ms        ? ?/sec
bundle/bundle@threejs-sourcemap                              1.00     44.7±0.77ms        ? ?/sec    1.00     44.6±0.54ms        ? ?/sec
bundle/bundle@threejs10x                                     1.00    388.7±3.35ms        ? ?/sec    1.03    401.6±6.49ms        ? ?/sec
bundle/bundle@threejs10x-sourcemap                           1.00    458.2±4.07ms        ? ?/sec    1.02    467.7±3.39ms        ? ?/sec
scan/scan@rome_ts                                            1.00     80.8±1.23ms        ? ?/sec    1.02     82.8±1.73ms        ? ?/sec
scan/scan@threejs                                            1.00     28.3±1.76ms        ? ?/sec    1.02     28.7±1.81ms        ? ?/sec
scan/scan@threejs10x                                         1.00    282.6±3.09ms        ? ?/sec    1.02    287.2±4.26ms        ? ?/sec

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Pull request overview

Copilot reviewed 38 out of 40 changed files in this pull request and generated 2 comments.

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crates/rolldown_dev/src/dev_engine.rs

graphite-app · 2026-01-05T12:23:55Z

Merge activity

Jan 5, 12:23 PM UTC: This pull request can not be added to the Graphite merge queue. Please try rebasing and resubmitting to merge when ready.
Jan 5, 12:23 PM UTC: Graphite disabled "merge when ready" on this PR due to: a merge conflict with the target branch; resolve the conflict and try again..
Jan 5, 12:24 PM UTC: The merge label 'graphite: merge-when-ready' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Jan 5, 12:45 PM UTC: graphite-app added this pull request to the Graphite merge queue.
Jan 5, 12:46 PM UTC: The Graphite merge queue couldn't merge this PR because it had merge conflicts.
Jan 5, 1:08 PM UTC: The merge label 'graphite: merge-when-ready' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Jan 5, 1:08 PM UTC: shulaoda added this pull request to the Graphite merge queue.
Jan 5, 1:19 PM UTC: Merged by the Graphite merge queue.

Same as #7609 but use stable module id instead of module id.

@shulaoda

## [1.0.0-beta.59] - 2026-01-07 ⚡ Inline Dynamic Imports for Statically Imported Modules - When a module is already statically imported, dynamic imports to that same module are now inlined instead of creating a separate chunk ### 🚀 Features - plugin_timings: add 3s threshold and doc link to warning message (#7741) by @shulaoda - improve treeshaking logic to handle empty parameter list in dynamic import .then() callbacks (#7781) by @Copilot - dev/lazy: don't include already executed modules (#7745) by @hyf0 - dev/lazy: support dynamic `import(..)` (#7726) by @hyf0 - inline dynamic imports that imports statically imported modules (#7742) by @IWANABETHATGUY - option: add experimental option to control chunk optimization (#7738) by @IWANABETHATGUY ### 🐛 Bug Fixes - inline dynamic entry to user defined entry with esm wrap kind (#7783) by @IWANABETHATGUY - use canonical namespace reference for property access (#7777) by @IWANABETHATGUY - dynamic entry merged into common chunk with cjs and esm wrap kind (#7771) by @IWANABETHATGUY - tla: should not await non-tla-related modules (#7768) by @hyf0 - dynamic entry captured by common chunk with CJS format (#7757) by @IWANABETHATGUY - module_loader: mark emitted chunks as user-defined entry when already loaded (#7765) by @shulaoda - normalize preserveModulesRoot path (#7737) by @IWANABETHATGUY - linker: resolve race condition in side effects computation for export-star (#7728) by @camc314 ### 🚜 Refactor - plugin_timings: filter out plugins with duration < 1s from timing warnings (#7785) by @shulaoda - module_loader: remove unnecessary collect before extend (#7769) by @shulaoda - rename _id suffixes to _idx for oxc_index types (#7767) by @IWANABETHATGUY - remove duplicate `preserve_entry_signatures` from `AddEntryModuleMsg` (#7762) by @shulaoda - module_loader: pass `user_defined_entries` by reference (#7756) by @shulaoda - dev/lazy: get proxy entry's `ResolvedId` correctly (#7746) by @hyf0 - simplify try_rewrite_import_expression control flow (#7753) by @IWANABETHATGUY - module_loader: remove unnecessary dynamic import handling for runtime module (#7754) by @shulaoda - inline __toDynamicImportESM (#7747) by @IWANABETHATGUY - use From impl for ModuleLoaderOutput conversion (#7732) by @shulaoda - remove duplicate fields from `ModuleLoader` (#7731) by @shulaoda - tweak `resolve_user_defined_entries` (#7727) by @shulaoda ### 📚 Documentation - add rolldown-string reference to native MagicString compatibility section (#7778) by @Copilot - improve comments for export star side effects handling (#7730) by @IWANABETHATGUY ### 🧪 Testing - use assertion instead of console.log for some testcase (#7744) by @IWANABETHATGUY ### ⚙️ Miscellaneous Tasks - tweak some `output.dynamicImportInCjs` related rollup test results (#7776) by @sapphi-red - mark esbuild/dce/dce_of_symbol_ctor_call as passed (#7775) by @sapphi-red - deps: update oxc apps (#7772) by @renovate[bot] - vite-tests: allow running on PRs with `test: vite-tests` label (#7770) by @shulaoda - deps: update oxc apps (#7760) by @renovate[bot] - deps: update rollup submodule for tests to v4.55.1 (#7763) by @sapphi-red - deps: update test262 submodule for tests (#7764) by @sapphi-red - deps: update oxc to v0.107.0 (#7758) by @camc314 - deps: update taiki-e/install-action action to v2.65.13 (#7751) by @renovate[bot] - deps: update rust crates (#7750) by @renovate[bot] - deps: update npm packages (#7749) by @renovate[bot] - deps: update github-actions (#7748) by @renovate[bot] - deps: update dependency oxlint-tsgolint to v0.10.1 (#7729) by @renovate[bot] - deps: update crate-ci/typos action to v1.41.0 (#7725) by @renovate[bot] Co-authored-by: shulaoda <[email protected]>

github-actions bot assigned hyf0 Dec 31, 2025

hyf0 changed the title ~~refactor(dev): use direct module id instead of stable id~~ feat(dev/lazy): use direct module id instead of stable id Dec 31, 2025

hyf0 changed the title ~~feat(dev/lazy): use direct module id instead of stable id~~ feat(dev/lazy): support dynamic import(..) Dec 31, 2025

hyf0 force-pushed the hyf_lazy_new branch 2 times, most recently from b199341 to ecfdf0c Compare January 1, 2026 12:00

hyf0 requested a review from sapphi-red January 1, 2026 20:45

hyf0 marked this pull request as ready for review January 1, 2026 20:45

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hyf0 force-pushed the hyf_lazy_new branch 2 times, most recently from 5e2f7a3 to 721ab37 Compare January 4, 2026 07:08

Copilot AI review requested due to automatic review settings January 4, 2026 15:42

hyf0 force-pushed the hyf_lazy_new branch from 721ab37 to 5736c0a Compare January 4, 2026 15:42

This was referenced Jan 4, 2026

feat(dev/lazy): don't include already executed modules #7745

Merged

refactor(dev/lazy): get proxy entry's ResolvedId correctly #7746

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crates/rolldown_dev/src/dev_engine.rs Show resolved Hide resolved

graphite-app bot added the graphite: merge-when-ready label Jan 5, 2026

shulaoda approved these changes Jan 5, 2026

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hyf0 force-pushed the hyf_lazy_new branch from 5736c0a to 93766ca Compare January 5, 2026 12:49

shulaoda added the graphite: merge-when-ready label Jan 5, 2026

feat(dev/lazy): support dynamic import(..) (#7726)

e8e1c20

Same as #7609 but use stable module id instead of module id.

graphite-app bot force-pushed the hyf_lazy_new branch from 93766ca to e8e1c20 Compare January 5, 2026 13:09

graphite-app bot merged commit e8e1c20 into main Jan 5, 2026
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graphite-app bot deleted the hyf_lazy_new branch January 5, 2026 13:19

graphite-app bot removed the graphite: merge-when-ready label Jan 5, 2026

This was referenced Jan 7, 2026

release: v1.0.0-beta.59 #7774

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release: v1.0.0-beta.59 #7786

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feat(dev/lazy): support dynamic `import(..)`#7726

feat(dev/lazy): support dynamic `import(..)`#7726
graphite-app[bot] merged 1 commit intomainfrom
hyf_lazy_new

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