expand: remove .is_dir() from path to avoid TOCTOU race

[oech3]

This should appear as read error.

[codspeed-hq]

Merging this PR will degrade performance by 4.67%

❌ 2 regressed benchmarks
✅ 325 untouched benchmarks
⏩ 46 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	sort_ascii_utf8_locale	15.4 ms	16.1 ms	-4.68%
❌	Simulation	sort_ascii_c_locale	16 ms	16.7 ms	-4.67%

Tip

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

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_{Comparing oech3:expand-is-dir (d99ddaa) with main (b76d615)}

Footnotes

1. 46 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[sylvestre]

sorry but i still don't see why it would be a TOCTOU issue

[oech3]

.is_dir() is done for file path instead of fd. So target file can be replaced by directory after .is_dir() returned false.

[sylvestre]

sure but it will just fail later

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/retry (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/printf/printf-surprise is now passing!

[oech3]

fail later means we are checking that target is directory twice with additional stat...

[sylvestre]

if i may, we have more important things to fix than this in the backlog