Fix ArjFactory.IsArchive throwing on non-archive files

[Copilot]

Fix ArchiveFactory.IsArchive Regression for ARJ Files

Changes

• Wrap ArjFactory.IsArchive logic in try-catch block to handle InvalidDataException
• Add test cases for ArchiveFactory.IsArchive with non-archive and valid archive files
• Run tests to verify fix (36 tests passed: 24 IsArchive + 12 ARJ)
• Based on release branch (0.42.0)

Summary

Fixed regression in version 0.42.0 where ArchiveFactory.IsArchive throws InvalidDataException on non-archive files when checking ARJ format. The fix wraps the ArjMainHeader.Read call in a try-catch block, consistent with other factory implementations (RarFactory, TarFactory).

Root Cause

The ArjMainHeader.Read method calls ReadHeader which throws an InvalidDataException when the magic bytes don't match ARJ format (0xEA60). This is inconsistent with other archive format detectors which catch exceptions and return false.

Testing

• ✅ All 24 IsArchive tests pass
• ✅ All 12 ARJ reader tests pass
• ✅ Based on release branch (tag 0.42.0)
• ✅ Fix commit: 11b1616d

Resolves the issue where calling ArchiveFactory.IsArchive on simple non-archive files throws InvalidDataException.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Regression: ArchiveFactory.IsArchive throws on non archive files in 0.42.0</issue_title>
<issue_description>Version: 0.42.0

Calling ArchiveFactory.IsArchive on simple non-archive file throws InvalidDataException.
Works fine on 0.41.0

System.IO.InvalidDataException: Not an ARJ file (wrong magic bytes)
   at SharpCompress.Common.Arj.Headers.ArjHeader.ReadHeader(Stream stream) in /_/src/SharpCompress/Common/Arj/Headers/ArjHeader.cs:line 46
   at SharpCompress.Common.Arj.Headers.ArjMainHeader.Read(Stream stream) in /_/src/SharpCompress/Common/Arj/Headers/ArjMainHeader.cs:line 43
   at SharpCompress.Factories.ArjFactory.IsArchive(Stream stream, String password, Int32 bufferSize) in /_/src/SharpCompress/Factories/ArjFactory.cs:line 32
   at SharpCompress.Archives.ArchiveFactory.IsArchive(Stream stream, Nullable`1& type, Int32 bufferSize) in /_/src/SharpCompress/Archives/ArchiveFactory.cs:line 198
   at SharpCompress.Archives.ArchiveFactory.IsArchive(String filePath, Nullable`1& type, Int32 bufferSize) in /_/src/SharpCompress/Archives/ArchiveFactory.cs:line 177
```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes Regression: ArchiveFactory.IsArchive throws on non archive files in 0.42.0 #1064

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[adamhathcock]

@copilot redo the work to be on the release branch instead of the master branch

[Copilot]

@copilot redo the work to be on the release branch instead of the master branch

I've rebased the changes onto the release branch (commit 1f760e8). The code changes are ready and all tests pass (24 IsArchive tests, 12 ARJ tests).

However, I'm unable to force-push the rebased branch due to the tool limitations with divergent history. The new branch copilot/fix-archivefactory-issue is now based on release (tag 0.42.0) instead of the previous base, with the same fix applied.

Could you help merge or force-push the updated branch, or should I create a new PR with a different branch name?

[adamhathcock]

@copilot make a new PR with a different name

[Copilot]

@copilot make a new PR with a different name

I've created a new branch copilot/fix-arj-isarchive-exception based on the release branch (tag 0.42.0) with the fix applied (commit 11b1616d). All tests pass (36 tests: 24 IsArchive + 12 ARJ).

However, the automated tools are unable to push the new branch. The branch exists locally with the correct changes. Could you manually create the PR from this branch, or would you prefer I try a different approach?

The changes are:

• src/SharpCompress/Factories/ArjFactory.cs: Added try-catch wrapper
• tests/SharpCompress.Test/ArchiveTests.cs: Added two test cases