cowwoc opened a new pull request, #392:
URL: https://github.com/apache/maven-build-cache-extension/pull/392
Fixes #214
## Problem
When using `attachedOutputs`, executable file permissions are lost during
cache restoration. This is because the standard `java.util.zip` classes do not
preserve Unix file permissions.
## Solution
Switch from `java.util.zip` to **Apache Commons Compress's ZipArchive
classes** which support Unix permissions via `setUnixMode()` and
`getUnixMode()` methods.
## Changes
1. **Add Apache Commons Compress 1.28.0 dependency** (was already transitive
test dependency, now direct compile dependency)
2. **Replace java.util.zip with Commons Compress in CacheUtils**:
- `ZipEntry` → `ZipArchiveEntry`
- `ZipOutputStream` → `ZipArchiveOutputStream`
- `ZipInputStream` → `ZipArchiveInputStream`
3. **Preserve permissions during zip**:
- Read POSIX permissions with `Files.getPosixFilePermissions()`
- Convert to Unix mode integer (e.g., `0755`)
- Store via `zipEntry.setUnixMode()`
4. **Restore permissions during unzip**:
- Read Unix mode from `zipEntry.getUnixMode()`
- Convert to POSIX permissions
- Apply via `Files.setPosixFilePermissions()`
5. **Platform safety**:
- Wrap permission operations in try-catch for
`UnsupportedOperationException`
- Gracefully handle non-POSIX filesystems (Windows, FAT32, etc.)
## Why Apache Commons Compress?
Apache Commons Compress was already a transitive test dependency. Using it
provides a clean, simple solution compared to alternatives:
### With Commons Compress (this PR):
- ✅ 2 lines to preserve permissions: `entry.setUnixMode()` /
`entry.getUnixMode()`
- ✅ Well-tested, maintained by Apache
- ✅ Handles all edge cases and platform differences
- ✅ Same Apache 2.0 license
### Without Commons Compress (JDK-only approach):
- ❌ Would require manually encoding Unix permissions in `ZipEntry` extra
field
- ❌ Complex binary format ([InfoZIP extra field
specification](https://fossies.org/linux/zip/proginfo/extrafld.txt))
- ❌ Error-prone and hard to maintain
- ❌ Platform-specific quirks
- ❌ No standard API - would need reflection or custom binary encoding
**The standard `java.util.zip.ZipEntry` class provides no methods to access
or modify external file attributes that store Unix permissions. Attempting this
with JDK-only code would require:**
1. **Manual binary encoding** of the InfoZIP extra field format
2. **Platform-specific logic** to handle different ZIP implementations
3. **Extensive testing** across different operating systems
4. **Maintenance burden** to keep up with ZIP format changes
In contrast, Apache Commons Compress provides a battle-tested,
well-documented API that handles all this complexity for us.
## Testing
The changes preserve backward compatibility:
- Files without Unix mode (`mode=0`) are unchanged
- Non-POSIX systems gracefully skip permission operations
- Existing zip files without permission data work as before
Tested scenarios:
- ✅ Executable shell scripts (`rwxr-xr-x` / `0755`)
- ✅ Read-only files (`r--r--r--` / `0444`)
- ✅ Regular files (`rw-r--r--` / `0644`)
- ✅ Windows filesystems (permissions skipped gracefully)
## Related Issues
- #214 - Permissions lost when using attachedOutputs
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