config_format: cf_yaml: Align the behavior of dirname against POSIX [Backport to 4.2]

[cosmo0920]

Backporting of #11345.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• Bug Fixes
  • Fixed path handling to properly normalize paths without a directory component by returning a canonical current-directory indicator instead of the original path.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Modified the dirname function in YAML config format handler to return "." when a path contains no directory component, instead of returning the original path. This aligns the Windows dirname behavior with POSIX standards for path extraction.

Changes

Cohort / File(s)	Summary
Path utility logic update src/config_format/flb_cf_yaml.c	Modified dirname function to return "." for paths without directory component (no backslash), previously returned original path. +3/-1 lines.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• #11345 — Makes the identical Windows dirname change to return "." when no directory component exists, aligning with POSIX behavior.

Suggested labels

docs-required

Suggested reviewers

• edsiper
• fujimotos
• koleini

Poem

🐰 A path once lost now finds its way,
With "." returned to lead the day,
Windows and POSIX now agree,
Standardized dirname, wild and free! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: aligning dirname behavior with POSIX standards in the cf_yaml module, and clearly indicates it's a backport to version 4.2.

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✨ Finishing touches

• 📝 Generate docstrings

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📜 Recent review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 797031c and 43c380a.

📒 Files selected for processing (1)

• src/config_format/flb_cf_yaml.c

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (31)

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🔇 Additional comments (1)

src/config_format/flb_cf_yaml.c (1)

532-546: LGTM! Correct POSIX alignment for Windows dirname().

The change properly aligns the Windows dirname() implementation with POSIX semantics by returning "." when no directory separator is found. This matches the expected behavior where dirname("filename") returns the current directory indicator.

Note: The function now has asymmetric return semantics—returning a modifiable buffer when a separator exists, versus an immutable string literal when it doesn't. This is acceptable here since callers (e.g., read_config() at line 2884) only read the path for concatenation purposes and don't attempt to modify it.

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