fix: treat only a whole file: URL as one when parsing a request

[alexander-akait]

Summary

parseIdentifier tested for a file URL with an unanchored /file:/i, so any request merely containing file: was handed to fileURLToPath and threw ERR_INVALID_URL: /foo/file:bar.js, ./a/file:b.js, and /tmp/profile:1.js — whose profile: contains file: — all crash resolution today. It now reuses the anchored isFileURL added in #668, so a file: inside a path segment stays part of the path and only a whole file:// URL is converted. That also leaves one definition of "is a file URL" in the codebase instead of two, and reads one character before any regexp runs on this hot path (the old test scanned the whole string).

What kind of change does this PR introduce?

fix.

Did you add tests for your changes?

Yes — test/identifier.test.js gains a file: in a path segment group (the four inputs above, one with a query and fragment) and a file: URLs group pinning what must still convert, percent-encoding and an upper-case scheme included. The four path-segment cases throw without the change.

Does this PR introduce a breaking change?

No — every request that resolved before still resolves; only the ones that threw now work. A single-slash file:/abs/x.js is no longer converted, but nothing produces that form (pathToFileURL and import.meta.resolve() both emit file:///…) and no test covered it.

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

n/a

Use of AI

Written with Claude Code. It found the unanchored test while working on #668, reproduced the crash, made the change and the tests, and ran the full lint and test suites locally (1544/1544 green); every claim above was verified by running it.

🤖 Generated with Claude Code

https://claude.ai/code/session_01TmnzpSwSysywhmNw9p3uT5

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Generated by Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: b034a55

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.14%. Comparing base (835c4fe) to head (b034a55).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #670   +/-   ##
=======================================
  Coverage   98.14%   98.14%           
=======================================
  Files          49       49           
  Lines       10042    10046    +4     
=======================================
+ Hits         9856     9860    +4     
  Misses        186      186           

Flag	Coverage Δ
integration	98.14% <100.00%> (+<0.01%)	⬆️

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[codspeed-hq]

Merging this PR will improve performance by 10.63%

⚡ 1 improved benchmark
✅ 141 untouched benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Memory	node-compare: node require.resolve x 1000	75.8 KB	68.5 KB	+10.63%

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Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing fix/file-url-request-detection (b034a55) with main (835c4fe)}