refactor: inline loader-runner package into core by bjohansebas · Pull Request #21249 · webpack/webpack

bjohansebas · 2026-06-22T19:48:45Z

Summary

This comes from the roadmap

Same content, just with typos.

What kind of change does this PR introduce?

Did you add tests for your changes?

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changeset-bot · 2026-06-22T19:48:50Z

🦋 Changeset detected

Latest commit: 262242f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
webpack	Patch

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codecov · 2026-06-22T19:51:21Z

Codecov Report

❌ Patch coverage is 95.44073% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.89%. Comparing base (6e5bd5d) to head (262242f).
⚠️ Report is 45 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/loaders/LoaderRunner.js	95.81%	12 Missing ⚠️
lib/loaders/loadLoader.js	91.17%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #21249      +/-   ##
==========================================
+ Coverage   92.77%   92.89%   +0.11%     
==========================================
  Files         591      597       +6     
  Lines       64467    65307     +840     
  Branches    17911    18243     +332     
==========================================
+ Hits        59808    60665     +857     
+ Misses       4659     4642      -17

Flag	Coverage Δ
css-parsing	`28.63% <29.26%> (-0.10%)`	⬇️
html5lib	`31.07% <29.26%> (-0.11%)`	⬇️
integration	`88.98% <85.10%> (+0.23%)`	⬆️
test262	`45.44% <30.48%> (-0.07%)`	⬇️
unit	`43.30% <94.20%> (+2.17%)`	⬆️

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…ation

- Introduced multiple loader implementations including identity, async, promise, and pitch loaders. - Added binary files for testing purposes, including 'bom.bin' and 'resource.bin'. - Implemented loaders that handle dependencies, context dependencies, and missing dependencies. - Created loaders that return modified source strings and handle raw data. - Added tests for loaders that throw errors and return promises. - Included examples of setting resource paths and handling async operations in loaders.

codspeed-hq · 2026-06-22T20:21:23Z

Merging this PR will not alter performance

⚠️

Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 4 improved benchmarks
❌ 3 regressed benchmarks
✅ 137 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Memory	`benchmark "asset-modules-inline", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}'`	381.2 KB	1,195.3 KB	-68.11%
❌	Memory	`benchmark "wasm-modules-sync", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}'`	131.8 KB	364.7 KB	-63.86%
❌	Memory	`benchmark "asset-modules-bytes", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}'`	247 KB	322.6 KB	-23.43%
⚡	Memory	`benchmark "many-modules-esm", scenario '{"name":"mode-development","mode":"development"}'`	1.9 MB	1.2 MB	+66.39%
⚡	Memory	`benchmark "many-chunks-esm", scenario '{"name":"mode-production","mode":"production"}'`	11.4 MB	8.7 MB	+31.34%
⚡	Memory	`benchmark "wasm-modules-async", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}'`	250.2 KB	195.3 KB	+28.13%
⚡	Memory	`benchmark "future-defaults", scenario '{"name":"mode-production","mode":"production"}'`	8.7 MB	7.1 MB	+23.58%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

_{Comparing bjohansebas:refactor/inline-loader-runner (262242f) with main (54fa902)}

…n LoaderRunner tests

…derRunner

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bjohansebas · 2026-06-22T21:30:19Z

@alexander-akait after this, I'm going to look into the improvements Rspack has regarding loader caching.

alexander-akait · 2026-06-26T13:30:42Z

+		missingDependencies.length = 0;
+		requestCacheable = true;
+	};
+	Object.defineProperty(loaderContext, "resource", {


Let's use modern ES syntax here, also I am thinking about implement a function createLoaderContext and move from normal module all logic related to loader context in this function, so it will be more readable, now we have multiple places to create a loader context, it is not good

… for improved structure

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…context management

bjohansebas · 2026-06-26T22:42:32Z

+
+	// add accessors last (keeps fast properties) and freeze, now that callers
+	// (e.g. NormalModule's beforeLoaders) have populated the context
+	Object.defineProperties(loaderContext, ACCESSORS);


Using defineProperties is consistently faster than defineProperty or class methods. I saw roughly a 9% performance improvement, especially in cases like Babel and other similar tooling.

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refactor: inline loader-runner package into core

b8f12e1

Copilot AI review requested due to automatic review settings June 22, 2026 19:48

Copilot AI reviewed Jun 22, 2026

bjohansebas marked this pull request as draft June 22, 2026 19:49

bjohansebas added 2 commits June 22, 2026 20:00

refactor: enhance LoaderContext type definitions and improve document…

ef97136

…ation

bjohansebas added 5 commits June 22, 2026 20:40

refactor: replace toBeInstanceOf with isError for error type checks i…

eced690

…n LoaderRunner tests

refactor: remove redundant checks for Object.preventExtensions in Loa…

57d28c8

…derRunner

refactor: add LoaderLoadingError class for improved error handling

a956356

refactor: optimize dynamic import handling in loadLoader function

34a73d5

fixup!

ef7abcf

bjohansebas marked this pull request as ready for review June 22, 2026 21:29

Copilot AI review requested due to automatic review settings June 22, 2026 21:29

Copilot AI reviewed Jun 22, 2026

refactor: enhance ESM loader support detection in runLoaders tests

edd9db2

alexander-akait reviewed Jun 26, 2026

View reviewed changes

refactor: replace createLoaderObject function with LoaderObject class…

1d2451f

… for improved structure

Copilot AI review requested due to automatic review settings June 26, 2026 19:55

Copilot AI reviewed Jun 26, 2026

refactor: introduce createLoaderContext function for improved loader …

79eb2d5

…context management

bjohansebas commented Jun 26, 2026

View reviewed changes

refactor: augment caller-provided context in runLoaders function

262242f

Copilot AI review requested due to automatic review settings June 26, 2026 22:49

Copilot AI reviewed Jun 26, 2026

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refactor: inline loader-runner package into core#21249

refactor: inline loader-runner package into core#21249
bjohansebas wants to merge 12 commits into
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bjohansebas:refactor/inline-loader-runner

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