Code Review

Reviewed PR adding compressed binary caching. The implementation integrates cachecompress.Compressor to serve binaries with on-demand compression and caching.

Summary of Changes

• Splits cache directory into compressed/ and orig/ subdirectories
• Wraps binary file server with cachecompress.Compressor when cache directory is provided
• Falls back to plain http.FileServer when no cache directory exists (testing scenarios)
• Updates binHandler to use generic http.Handler instead of concrete http.FileSystem
• Updates comment to reflect new orig/ subdirectory path

Issues to Address

1. Missing dependency documentation (line 25): This PR depends on the cachecompress package which doesn't exist on main branch yet. The PR description should explicitly document which PR introduces it and the merge order dependency.

2. Undocumented constant (line 28): CompressionLevel is exported but lacks a doc comment. Should explain why level 5 was chosen:

   // CompressionLevel is the gzip/deflate compression level used for binary caching.
   // Level 5 provides a good balance between compression ratio and CPU usage.
   const CompressionLevel = 5

3. Inconsistent terminology (line 105): Error comment uses "cached dir" but elsewhere uses "cache dir". Should be consistent:

   // cache dir was provided, but we can't write to it

4. Missing test coverage: No tests verify the new caching behavior. Should add tests for:

   • Binary files are compressed and cached correctly
   • Compressed files served with proper Content-Encoding headers
   • Fallback to uncompressed serving when cache dir is empty
   • Cache directory structure created correctly (compressed/ and orig/ subdirs)
   • Error handling when cache directory creation fails

Positive Notes

• ✅ Error handling properly wraps errors with xerrors.Errorf
• ✅ Secure file permissions (0o700 for directories)
• ✅ Good fallback behavior for testing scenarios
• ✅ Import organization follows Go conventions
• ✅ Clear comment explaining ExtractOrReadBinFS behavior with empty cacheDir