Apply extensionAlias to imports-field resolutions

[alexander-akait]

Summary

Closes part of #413 (the imports field half).

extensionAlias is tapped on raw-resolve and keys off request.request. When a request is resolved through the package.json imports field, ImportsFieldPlugin bypasses raw-resolve and hands off to the relative hook with request: undefined (only request.path is set), so TypeScript-style extension substitution (.js → .ts) never fires for internal subpath imports like #foo. This made extensionAlias unusable together with the imports field — the exact setup eslint-import-resolver-typescript needs.

Unlike the exports field, the imports field is internal to the package, so applying the consumer's aliases does not expose files the package author never meant to expose (the concern raised in #355 / #413). For that reason this enables the behavior by default for imports only; the exports side can still be discussed as an opt-in later.

Before

// package.json: { "imports": { "#foo": "./foo.js" } }
// files: foo.ts, foo.js
resolve({ extensionAlias: { ".js": [".ts", ".js"] } }, dir, "#foo")
// -> foo.js  (extensionAlias ignored)

resolve({ extensionAlias: { ".js": [".ts", ".js"] } }, dir, "./foo.js")
// -> foo.ts  (works, asymmetric)

After

resolve({ extensionAlias: { ".js": [".ts", ".js"] } }, dir, "#foo")
// -> foo.ts  (consistent with ./foo.js)

Changes

• ExtensionAliasPlugin: handle both the existing "request" mode (specifier-based) and a new "path" mode (when request.request === undefined, operate on request.path / request.relativePath).
• ResolverFactory: introduce an imports-field-relative hook between ImportsFieldPlugin and relative, tap per-alias plugins there, and forward to relative by default via NextPlugin. ExportsFieldPlugin is left untouched.
• Tests: 4 new cases in test/extension-alias.test.js covering the primary alias, fallback to later alternatives, strict (no-fallback) mapping, and single-string alias.

Test plan

• npx jest — 996 passing (992 before + 4 new)
• npx jest test/extension-alias.test.js — 12 passing
• npx tsc — clean
• npx eslint lib/ExtensionAliasPlugin.js lib/ResolverFactory.js test/extension-alias.test.js — clean
• Manual check: exports-field resolution (self-ref/foo → foo.js) unchanged

https://claude.ai/code/session_01JGjZtthJN27rDbRPUAPjQh

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[linux-foundation-easycla]

• ✅ login: alexander-akait / name: Alexander Akait (418fd35)
• ❌ - login: @claude / name: Claude . The commit (3b7e68f, 5503fa2) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

[changeset-bot]

🦋 Changeset detected

Latest commit: 418fd35

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

This PR includes changesets to release 1 package

Name	Type
enhanced-resolve	Patch

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[codecov]

Codecov Report

❌ Patch coverage is 95.23810% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.57%. Comparing base (ed92a94) to head (418fd35).
⚠️ Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/ExtensionAliasPlugin.js	94.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #549      +/-   ##
==========================================
- Coverage   96.58%   96.57%   -0.02%     
==========================================
  Files          50       50              
  Lines        2783     2800      +17     
  Branches      850      863      +13     
==========================================
+ Hits         2688     2704      +16     
- Misses         79       80       +1     
  Partials       16       16              

Flag	Coverage Δ
integration	96.57% <95.23%> (-0.02%)	⬇️

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[codspeed-hq]

Merging this PR will not alter performance

✅ 69 untouched benchmarks

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_{Comparing claude/review-issue-413-rygbg (418fd35) with main (ed92a94)}