fix: MSGToDocument raises KeyError on ByteStream sources without file_path

[mittalpk]

Related Issues

• No existing issue filed; found via a direct code audit of MSGToDocument, not a bug report.

Proposed Changes

MSGToDocument.run() builds attachment metadata via merged_metadata["file_path"], but merged_metadata only contains "file_path" when the source was a str/Path (auto-populated by get_bytestream_from_source) or a ByteStream whose own meta happens to include it. A bare ByteStream(data=...) source — explicitly supported by the method's type signature (sources: list[str | Path | ByteStream]), and the exact pattern shown for other converters' ByteStream.from_string/manual-construction usage — has no such key. Converting a .msg file with attachments from such a source therefore raised an uncaught KeyError: 'file_path' instead of producing documents, crashing the whole run() call rather than just that one source.

Fixed by only setting parent_file_path on the attachment metadata when a source file_path is actually available, leaving it out otherwise instead of crashing.

How did you test it?

Reproduced the crash directly against main with a minimal script (MSGToDocument().run(sources=[ByteStream(data=open("test/test_files/msg/sample.msg","rb").read())])), confirmed the exact KeyError.

Added test_run_bytestream_without_file_path, confirmed it fails on unpatched msg.py (git stash) with the same KeyError, and passes after the fix. Ran the full converters unit suite (hatch run test:unit test/components/converters/) — 263 passed, no regressions. hatch run test:types — no issues. hatch run fmt — clean.

Notes for the reviewer

Small, behavior-preserving fix — no change for the existing (and already-tested) file-path-source path; only the previously-crashing ByteStream-without-file_path path changes, from an exception to a document/attachment without a parent_file_path key.

Checklist

• I have read the contributors guidelines and the code of conduct.
• I have added unit tests and updated the docstrings.
• I've used a conventional commit type (fix:) for the PR title.
• I have added a release note file.
• I have run hatch run fmt / hatch run test:types / hatch run test:unit and fixed any issue.

This PR was developed with AI-assisted tooling (Claude Code); I reviewed the diagnosis, the fix, and the test, and ran the test suite and quality checks locally as noted above.

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