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fix: write emitted assets with an absolute path as-is#21223

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claude/webpack-12759-tests-6spajo
Jun 20, 2026
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fix: write emitted assets with an absolute path as-is#21223
alexander-akait merged 2 commits into
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claude/webpack-12759-tests-6spajo

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@alexander-akait

@alexander-akait alexander-akait commented Jun 19, 2026

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Summary

Emitting an asset whose name is an absolute path threw EINVAL on Windows: the absolute targetFile was joined onto output.path, producing an invalid path such as C:\out\D:\file. Absolute target files are now written to their absolute location as-is.

While here, the scattered "is this path absolute" checks — each a slightly different regex, several of which missed forward-slash Windows paths like C:/dir — are consolidated onto a single cross-platform ABSOLUTE_PATH_REGEXP (equal to path.posix.isAbsolute || path.win32.isAbsolute), reused in Compiler, util/fs isAbsolute, extractSourceMap, NormalModule, CleanPlugin and the sharing plugins.

Also fixes output.path set to the filesystem root: memfs and some platforms throw EISDIR (not EEXIST) when mkdir targets an existing directory such as /, which mkdirp/mkdirpSync now treat as already-existing.

Closes #12759
Closes #20403
Closes #12906
Closes #10544

What kind of change does this PR introduce?

fix

Did you add tests for your changes?

Yes — a Windows-only configCase test/configCases/emit-asset/absolute-path that emits an asset to an absolute path, a configCase test/configCases/emit-asset/mkdir-eisdir that wraps the output file system so mkdir reports EISDIR for existing dirs, and unit tests for ABSOLUTE_PATH_REGEXP in test/identifier.unittest.js.

Does this PR introduce a breaking change?

No.

If relevant, what needs to be documented once your changes are merged or what have you already documented?

n/a

Use of AI

AI (Claude Code) was used to investigate the issues, implement the fixes, consolidate the absolute-path checks, and write the tests. All changes were reviewed by a human before submitting.


Generated by Claude Code

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changeset-bot Bot commented Jun 19, 2026

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🦋 Changeset detected

Latest commit: a99b760

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

This PR includes changesets to release 1 package
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webpack Patch

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This PR is packaged and the instant preview is available (6e5bd5d).

Install it locally:

  • npm
npm i -D webpack@https://pkg.pr.new/webpack@6e5bd5d
  • yarn
yarn add -D webpack@https://pkg.pr.new/webpack@6e5bd5d
  • pnpm
pnpm add -D webpack@https://pkg.pr.new/webpack@6e5bd5d

@alexander-akait alexander-akait force-pushed the claude/webpack-12759-tests-6spajo branch from 14ec71a to d556115 Compare June 19, 2026 12:46
@codecov

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Codecov Report

❌ Patch coverage is 88.46154% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.76%. Comparing base (5ba1265) to head (a99b760).

Files with missing lines Patch % Lines
lib/util/fs.js 57.14% 3 Missing ⚠️

❌ Your patch check has failed because the patch coverage (88.46%) is below the target coverage (90.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files
@@            Coverage Diff             @@
##             main   #21223      +/-   ##
==========================================
- Coverage   92.77%   92.76%   -0.02%     
==========================================
  Files         591      591              
  Lines       64458    64467       +9     
  Branches    17908    17911       +3     
==========================================
- Hits        59802    59801       -1     
- Misses       4656     4666      +10     
Flag Coverage Δ
css-parsing 28.72% <55.55%> (+<0.01%) ⬆️
html5lib 31.17% <55.55%> (+<0.01%) ⬆️
integration 88.73% <88.46%> (-0.02%) ⬇️
test262 45.54% <61.11%> (+0.04%) ⬆️
unit 41.12% <33.33%> (+<0.01%) ⬆️

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@alexander-akait alexander-akait force-pushed the claude/webpack-12759-tests-6spajo branch from d556115 to 1cda4bb Compare June 19, 2026 12:56
@codspeed-hq

codspeed-hq Bot commented Jun 19, 2026

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Merging this PR will degrade performance by 51.39%

⚠️ 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

⚡ 1 improved benchmark
❌ 4 regressed benchmarks
✅ 139 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

Mode Benchmark BASE HEAD Efficiency
Memory benchmark "side-effects-reexport", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}' 128.4 KB 859.1 KB -85.05%
Memory benchmark "asset-modules-bytes", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}' 246 KB 889.3 KB -72.34%
Memory benchmark "wasm-modules-sync", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}' 251.9 KB 358.9 KB -29.83%
Memory benchmark "many-modules-esm", scenario '{"name":"mode-production","mode":"production"}' 7.2 MB 9.3 MB -22.14%
Memory benchmark "many-chunks-commonjs", scenario '{"name":"mode-production","mode":"production"}' 9.1 MB 7.6 MB +20.15%

Tip

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


Comparing claude/webpack-12759-tests-6spajo (a99b760) with main (5ba1265)

Open in CodSpeed

@alexander-akait alexander-akait force-pushed the claude/webpack-12759-tests-6spajo branch from 1cda4bb to 7250f2f Compare June 19, 2026 13:01
Joining an absolute targetFile onto output.path produced an invalid
path on Windows (e.g. C:\out\D:\file) and threw EINVAL. Detect an
absolute target file and write it to that location directly.

Introduce a single cross-platform ABSOLUTE_PATH_REGEXP (POSIX /foo plus
every Windows form: drive-letter C:\ and C:/, UNC, rooted), equal to
path.posix.isAbsolute || path.win32.isAbsolute, and reuse it as the one
absolute-path check across the codebase: Compiler, util/fs isAbsolute,
extractSourceMap, NormalModule (also fixes the forward-slash gap from
#20403), CleanPlugin and the sharing plugins.

Closes #12759
@alexander-akait alexander-akait force-pushed the claude/webpack-12759-tests-6spajo branch from 7250f2f to 2dba99b Compare June 19, 2026 13:23
memfs and some platforms throw EISDIR (not EEXIST) when mkdir targets an
existing directory such as the root "/", which made output.path "/" fail.
Treat EISDIR like EEXIST in mkdirp/mkdirpSync (#10544).
@alexander-akait alexander-akait force-pushed the claude/webpack-12759-tests-6spajo branch from dc2781b to a99b760 Compare June 19, 2026 15:43
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Types Coverage

Coverage after merging claude/webpack-12759-tests-6spajo into main will be
99.35%
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@alexander-akait alexander-akait merged commit 6e5bd5d into main Jun 20, 2026
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@alexander-akait alexander-akait deleted the claude/webpack-12759-tests-6spajo branch June 20, 2026 02:11
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Target files on different drive than the output path cause invalid path and error is thrown webpack 5 can't set output path to /

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