fix(rust/dev): error of `bundler.scan`doesn't get handled by Copilot · Pull Request #6547 · rolldown/rolldown

Copilot · 2025-10-15T10:54:09Z

Fixes an issue where errors from bundler.scan() in the dev engine were not being properly handled and reported through the on_output callback.

Problem

In crates/rolldown/src/dev/building_task.rs, when bundler.scan() failed during a rebuild, the error was immediately propagated using the ? operator:

let scan_output = bundler.scan(scan_mode).await?;  // Error propagates here
let build_result = if skip_write {
  bundler.bundle_generate(scan_output).await
} else {
  bundler.bundle_write(scan_output).await
};

// on_output callback is called here, but unreachable if scan fails
if let Some(on_output) = self.dev_context.options.on_output.as_ref() {
  on_output(build_result);
}

This meant that when scan failed, the on_output callback was never invoked, and errors were only printed to stderr instead of being properly reported to the dev engine's error handling mechanism.

Solution

Modified the error handling to capture scan errors and pass them to the on_output callback:

let scan_output = bundler.scan(scan_mode).await;
let build_result = match scan_output {
  Ok(scan_output) => {
    if skip_write {
      bundler.bundle_generate(scan_output).await
    } else {
      bundler.bundle_write(scan_output).await
    }
  }
  Err(scan_error) => Err(scan_error),
};

// Now scan errors are properly passed to on_output callback
if let Some(on_output) = self.dev_context.options.on_output.as_ref() {
  on_output(build_result);
}

This ensures scan errors are properly reported through the dev engine's callback mechanism, consistent with how other build errors (from bundle_generate and bundle_write) are handled.

Closes #6319

Original prompt

This section details on the original issue you should resolve

<issue_title>bundler.scan's error doesn't get handled in dev engine</issue_title>
<issue_description>> Should be a problem here

rolldown/crates/rolldown/src/dev/building_task.rs

Line 253 in 8b9b459

let scan_output = bundler.scan(scan_mode).await?;

I'll fix right away.

Originally posted by @hyf0 in #6319</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #6546

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

graphite-app · 2025-10-15T10:54:16Z

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netlify · 2025-10-15T10:55:27Z

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hyf0 · 2025-10-15T11:04:33Z

@copilot No need to add test so far.

hyf0 · 2025-10-15T11:17:53Z

Merge activity

Oct 15, 11:17 AM UTC: The merge label 'graphite: merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Oct 15, 11:21 AM UTC: hyf0 added this pull request to the Graphite merge queue.
Oct 15, 11:35 AM UTC: Merged by the Graphite merge queue.

@hyf0

Fixes an issue where errors from `bundler.scan()` in the dev engine were not being properly handled and reported through the `on_output` callback. ## Problem In `crates/rolldown/src/dev/building_task.rs`, when `bundler.scan()` failed during a rebuild, the error was immediately propagated using the `?` operator: ```rust let scan_output = bundler.scan(scan_mode).await?; // Error propagates here let build_result = if skip_write { bundler.bundle_generate(scan_output).await } else { bundler.bundle_write(scan_output).await }; // on_output callback is called here, but unreachable if scan fails if let Some(on_output) = self.dev_context.options.on_output.as_ref() { on_output(build_result); } ``` This meant that when scan failed, the `on_output` callback was never invoked, and errors were only printed to stderr instead of being properly reported to the dev engine's error handling mechanism. ## Solution Modified the error handling to capture scan errors and pass them to the `on_output` callback: ```rust let scan_output = bundler.scan(scan_mode).await; let build_result = match scan_output { Ok(scan_output) => { if skip_write { bundler.bundle_generate(scan_output).await } else { bundler.bundle_write(scan_output).await } } Err(scan_error) => Err(scan_error), }; // Now scan errors are properly passed to on_output callback if let Some(on_output) = self.dev_context.options.on_output.as_ref() { on_output(build_result); } ``` This ensures scan errors are properly reported through the dev engine's callback mechanism, consistent with how other build errors (from `bundle_generate` and `bundle_write`) are handled. Closes #6319  <details> <summary>Original prompt</summary> > > ---- > > *This section details on the original issue you should resolve* > > <issue_title>`bundler.scan`'s error doesn't get handled in dev engine</issue_title> > <issue_description>> Should be a problem here<br><br>[https://github.com/rolldown/rolldown/blob/8b9b459da8b36a2a546de014c78a41550af58d61/crates/rolldown/src/dev/building_task.rs#L253](https://github.com/rolldown/rolldown/blob/8b9b459da8b36a2a546de014c78a41550af58d61/crates/rolldown/src/dev/building_task.rs#L253)<br><br>I'll fix right away. > > _Originally posted by @hyf0 in [#6319](https://github.com/rolldown/rolldown/issues/6319#issuecomment-3405824641)_</issue_description> > > ## Comments on the Issue (you are @copilot in this section) > > <comments> > </comments> > </details> Fixes #6546  --- ✨ Let Copilot coding agent [set things up for you](https://github.com/rolldown/rolldown/issues/new?title=✨+Set+up+Copilot+instructions&body=Configure%20instructions%20for%20this%20repository%20as%20documented%20in%20%5BBest%20practices%20for%20Copilot%20coding%20agent%20in%20your%20repository%5D%28https://gh.io/copilot-coding-agent-tips%29%2E%0A%0A%3COnboard%20this%20repo%3E&assignees=copilot) — coding agent works faster and does higher quality work when set up for your repo.

github-actions · 2025-10-15T11:38:20Z

Benchmarks Rust

target: main(1937754)
pr: copilot/fix-bundler-scan-error(b28d2ad)

group                                                        pr                                     target
-----                                                        --                                     ------
bundle/bundle@multi-duplicated-top-level-symbol              1.01     69.5±2.30ms        ? ?/sec    1.00     68.9±1.94ms        ? ?/sec
bundle/bundle@multi-duplicated-top-level-symbol-sourcemap    1.00     74.4±1.94ms        ? ?/sec    1.05     77.8±1.62ms        ? ?/sec
bundle/bundle@rome_ts                                        1.00    109.4±2.92ms        ? ?/sec    1.01    110.7±1.55ms        ? ?/sec
bundle/bundle@rome_ts-sourcemap                              1.00    121.6±1.94ms        ? ?/sec    1.01    123.3±2.25ms        ? ?/sec
bundle/bundle@threejs                                        1.00     44.0±1.08ms        ? ?/sec    1.02     44.7±2.41ms        ? ?/sec
bundle/bundle@threejs-sourcemap                              1.00     47.3±1.52ms        ? ?/sec    1.00     47.5±0.66ms        ? ?/sec
bundle/bundle@threejs10x                                     1.00    429.4±6.10ms        ? ?/sec    1.00    429.2±7.94ms        ? ?/sec
bundle/bundle@threejs10x-sourcemap                           1.01    485.6±3.85ms        ? ?/sec    1.00    480.4±4.79ms        ? ?/sec
scan/scan@rome_ts                                            1.01     88.0±1.49ms        ? ?/sec    1.00     87.3±1.57ms        ? ?/sec
scan/scan@threejs                                            1.00     33.2±1.98ms        ? ?/sec    1.00     33.2±2.06ms        ? ?/sec
scan/scan@threejs10x                                         1.01    336.4±4.29ms        ? ?/sec    1.00    332.8±5.55ms        ? ?/sec

@sapphi-red

## [1.0.0-beta.44] - 2025-10-20 :boom: Breaking Changes - Top-level `jsx` removed, use `transform.jsx` instead - `output.minifyInternalExports` now enabled by default :dart: Enhanced Tree-Shaking - JSON default imports are now tree-shakeable ```js // config.json { "apiUrl": "[https://api.example.com](https://api.example.com/)", "timeout": 5000, "retries": 3, "debug": false } // main.js // Before: Entire JSON was included in bundle import config from './config.json'; console.log(config.apiUrl); // After: Only the used property is included // Bundle now contains just the apiUrl value ``` - Built-in typed array constructors (`new Uint8Array()`, `new Int32Array()`, etc.) marked as pure :gear: Configuration Improvements - Support `output.cleanDir` option - Deprecated some top-level options - `define` → `transform.define` - `inject` → `transform.inject` - `dropLabels` → `transform.dropLabels` - `keepNames` → `output.keepNames` - `profilerNames` → `output.generatedCode.profilerNames` ### 💥 BREAKING CHANGES - enable `output.minifyInternalExports` for `format: 'es'` or `minify: true` (#6594) by @sapphi-red - node/options: remove `InputOptions.jsx`, prefer `transform.jsx` always (#6548) by @hyf0 ### 🚀 Features - support jsx preset for `transform.jsx` (#6630) by @shulaoda - rolldown_plugin_vite_html: align `inject_to_body` function (#6622) by @shulaoda - rolldown_vite_css_post_plugin: tweak `is_legacy` field (#6620) by @shulaoda - native-plugin: expose `viteHtmlPlugin` (#6609) by @shulaoda - native-plugin: expose `viteCSSPostPlugin` (#6606) by @shulaoda - builtin-plugin: expose `viteCSSPlugin` (#6605) by @shulaoda - rolldown_plugin_vite_html: complete plugin binding (#6604) by @shulaoda - rolldown_plugin_vite_css: support plugin binding (#6598) by @shulaoda - add TypedArray constructors to side-effect free globals (#6592) by @IWANABETHATGUY - rolldown_plugin_vite_html: align process src attr logic (#6572) by @shulaoda - rolldown: support `output.clearDir` to clean up `dir` before build (#6486) by @aprosail - dev: return `RolldownOutput` instead of `BindingOutputs` from `onOutput` (#6563) by @sapphi-red - rolldown_plugin_vite_html: align process srcset logic (#6560) by @shulaoda - rolldown_plugin_vite_html: align process src function (#6559) by @shulaoda - rolldown_plugin_vite_html: align parse secset function (#6558) by @shulaoda - node/options: deprecate `dropLabels` and add `transform.dropLabels` (#6557) by @hyf0 - node/options: deprecate `keepNames` and add `output.keepNames` (#6556) by @hyf0 - node/options: deprecate `profilerNames` and add `output.generatedCode.profilerNames` (#6555) by @hyf0 - node/options: deprecate top level `inject` and `define` and add `transform.define`, `transform.inject` (#6544) by @hyf0 - rolldown_plugin_vite_html: initialize attributes handle logic (#6543) by @shulaoda - rolldown: oxc v0.95.0 (#6541) by @Boshen - rolldown_plugin_vite_html: align inject css logic (#6528) by @shulaoda - rolldown_plugin_vite_html: align modulepreload inject logic (#6526) by @shulaoda - rolldown_plugin_vite_html: align css bundle output inject logic (#6524) by @shulaoda - rolldown_plugin_vite_html: support inject_to_head function (#6522) by @shulaoda - rolldown_plugin_vite_html: align emit and delete logic (#6521) by @shulaoda - rolldown_vite_html: align handle html asset url logic (#6518) by @shulaoda - add an example how to transform code and generate sourcemap with `experimental.nativeMagicString` (#6514) by @IWANABETHATGUY - rolldown_plugin_vite_html: align handle inline css logic (#6517) by @shulaoda ### 🐛 Bug Fixes - native-plugin: use correct config for assetPlugin (#6638) by @shulaoda - no_color not being respected on reporter (#6615) by @H4ad - improve tree shaking for JSON default imports (#6626) by @IWANABETHATGUY - cjs treeshaking removes used code (#6597) by @IWANABETHATGUY - plugin/vite-resolve: return `package_json_path` from resolveId hook (#6434) by @sapphi-red - dev: `should have idx` error happens with `deferSyncScanData` + incremental rebuild (#6568) by @sapphi-red - rolldown: sync scoping properly in pre_process_ecma_ast (#6537) by @Boshen - process CJS tree shaking bailout modules before eliminating unused dynamic entries (#6549) by @IWANABETHATGUY - rust/dev: error of `bundler.scan`doesn't get handled (#6547) by @Copilot - inline only self referenced json module properties (#6519) by @IWANABETHATGUY - avoid processing native MagicString sourcemap when `sourcemap` is disabled (#6510) by @IWANABETHATGUY ### 🚜 Refactor - rolldown_binding: unify `BindingAssetInlineLimit` (#6625) by @shulaoda - rolldown_binding: tweak `BindingAssetPluginConfig` (#6624) by @shulaoda - tweak `viteCSSPlugin` config (#6610) by @shulaoda - rust/dev: remove unnecessary bundler cache management of dev engine (#6576) by @hyf0 - rust/dev: refactor `TaskInput` into enum to reduce invalid states (#6575) by @hyf0 - improve the error message of `ScanStageCache#merge` (#6564) by @IWANABETHATGUY - rust/dev: use `client_id` to check if module is executed for test environment (#6566) by @hyf0 - rust/binding: mark napi object that won't be received from js side (#6531) by @hyf0 - rust/binding: mark napi object struct that won't be passed to js explicitly (#6525) by @hyf0 - rust/binding: use `&str` or `JsString` to avoid unnecessary clone (#6523) by @hyf0 - rust/binding: use `&str` to avoid unnecessary clone (#6520) by @hyf0 - rust: replace unwrap with expect for better error handling in message sending (#6509) by @hyf0 ### 📚 Documentation - add redirect from `/guide/in-depth/` to `/in-depth/` (#6554) by @Copilot - guide: polish notable features page (#6535) by @sapphi-red - builtin-plugins: add replace plugin docs (#6534) by @sapphi-red - add `Additional Thanks` in `acknowledgements` page (#6507) by @hyf0 - polish doc for `experimental.nativeMagicString` (#6504) by @IWANABETHATGUY ### ⚡ Performance - cli: advance `createTokioRuntime` (#6618) by @hyf0 - rolldown: reduce unnecessary Vec allocate (#6601) by @Brooooooklyn - rolldown: make derived assets generation more parallel (#6600) by @Brooooooklyn - rolldown: make chunks generation more parallel (#6599) by @Brooooooklyn - rolldown_utils: only allocate HASH_PLACEHOLDER_LEFT once (#6595) by @Brooooooklyn - rolldown: use oxc-resolver with simd-json (#6591) by @Boshen - rolldown: avoid allocate the sourcemap sources on non Windows os (#6590) by @Brooooooklyn - resolver: use optimized fs.read_to_string impl (#6589) by @Brooooooklyn - deps: upgrade json-escape-simd and add simdutf8 dependency (#6579) by @Brooooooklyn - rust/dev: remove unncessary clone for `ClientInput` (#6565) by @hyf0 - visit ast in `cross_module_optimization` stage parallel (#6552) by @IWANABETHATGUY ### 🧪 Testing - json module prop conflict with normal module declaration binding (#6540) by @IWANABETHATGUY - vite-tests: fix rolldown overrides (#6532) by @sapphi-red ### ⚙️ Miscellaneous Tasks - remove string conversion warning in `replacePlugin` to compatible with rollup (#6639) by @IWANABETHATGUY - deps: update dependency dprint-json to v0.21.0 (#6637) by @renovate[bot] - deps: lock file maintenance (#6635) by @renovate[bot] - deps: lock file maintenance npm packages (#6632) by @renovate[bot] - node: use built-in styleText (#6340) by @dumbmatter - deps: update actions/setup-node action to v6 (#6629) by @renovate[bot] - deps: update github-actions (#6628) by @renovate[bot] - deps: update dependency dprint-markdown to v0.20.0 (#6627) by @renovate[bot] - Switch color dependencies (ansis and picocolors) to built-in styleText (#6619) by @IWANABETHATGUY - native-plugin: tweak assetPlugin (#6623) by @shulaoda - remove deprecated warning in `build.ts` (#6621) by @IWANABETHATGUY - deps: update dependency tsdown to v0.15.8 (#6617) by @renovate[bot] - rolldown_binding: rename vite css plugin config field (#6611) by @shulaoda - add colored deprecation warnings for top-level options (#6612) by @IWANABETHATGUY - rust: make `cargo publish --workspace` work (#6287) by @Boshen - deps: update dependency rolldown-plugin-dts to v0.16.12 (#6608) by @renovate[bot] - test: add `opposite_minify_internal_exports` and remove `minify_internal_exports` extend test (#6596) by @hyf0 - test: render snapshot for build and dev independently (#6584) by @hyf0 - test: split test logic for normal build and dev engine (#6580) by @hyf0 - fix rolldown build self warning (#6578) by @IWANABETHATGUY - tweak `BindingBuiltinPluginName` (#6574) by @shulaoda - rust: use forked `notify` crate (#6573) by @Boshen - add `.len()` and `.is_empty()` to `HybridIndexVec` (#6570) by @sapphi-red - ai: improve `AGENT.md` with verified prompts (#6533) by @hyf0 - clippy: set `too-many-lines-threshold` to 200 (#6530) by @shulaoda - clean up examples/basic-vue (#6515) by @IWANABETHATGUY - deps: update dependency tsdown to v0.15.7 (#6512) by @renovate[bot] - add shulaoda to release PR assignees (#6505) by @shulaoda ### ❤️ New Contributors * @dumbmatter made their first contribution in [#6340](#6340) * @H4ad made their first contribution in [#6615](#6615) * @aprosail made their first contribution in [#6486](#6486) Co-authored-by: shulaoda <165626830+shulaoda@users.noreply.github.com>

Copilot AI assigned Copilot and hyf0 Oct 15, 2025

Copilot started work on behalf of hyf0 October 15, 2025 10:54 View session

Copilot AI changed the title ~~[WIP] Fix bundler.scan error handling in development engine~~ Fix bundler.scan error handling in dev engine Oct 15, 2025

Copilot AI requested a review from hyf0 October 15, 2025 11:07

Copilot finished work on behalf of hyf0 October 15, 2025 11:07

Copilot started work on behalf of hyf0 October 15, 2025 11:07 View session

Copilot finished work on behalf of hyf0 October 15, 2025 11:09

hyf0 changed the title ~~Fix bundler.scan error handling in dev engine~~ fix(rust/dev): error of bundler.scandoesn't get handled Oct 15, 2025

hyf0 marked this pull request as ready for review October 15, 2025 11:17

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Handle error in dev #6319

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release: v1.0.0-beta.44 #6640

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fix(rust/dev): error of `bundler.scan`doesn't get handled#6547

fix(rust/dev): error of `bundler.scan`doesn't get handled#6547
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