fix(epub): recognize XML elements independently of namespace prefixes

[Alex (ac1982)]

EPUB conversion depends on XML prefix spelling. A container using <ocf:rootfile> raises IndexError; a package using <opf:item>/<opf:itemref> silently loses chapter content; changing the Dublin Core dc: prefix drops metadata.

Resolve elements by namespace URI and local name. If the standard namespace has no matching elements, retain the previous exact tag-name lookup (rootfile, item, itemref, or dc:…). This preserves the existing tolerance for missing, legacy and malformed namespace URIs without matching arbitrary foreign local names. The private text helpers are only used for Dublin Core fields.

Three generated-archive regressions cover container/package/metadata prefixes and spine ordering. Following review, six additional cases cover the OEB 1.2 package namespace, Dublin Core 1.0, the missing-slash DC URI, an alternate container URI, and unnamespaced container/package elements. The first four fail at the previous PR head, including silent chapter/metadata loss; all pass after restoring the fallback. The test entry point is now below all test definitions.

Validation on Python 3.12 / Linux arm64:

• PYTHONPATH=packages/markitdown/src .venv/bin/python -m pytest packages/markitdown/tests -q: 1103 passed, 12 skipped, 1 failed because the local FLAC executable was missing.
• After installing FLAC, the failed speech-transcription test and the complete EPUB file passed together: 18 passed. Direct execution of test_epub.py also collected and passed all 17 cases. The full suite was not rerun after installing the dependency.
• python -m pre_commit run --all-files: passed (Black 23.7.0); git diff --check: passed.
• Windows/macOS, a real-world prefixed EPUB and live LLM conversion were not validated by the author. Generated archives exercise the public converter.

Searched existing issues and all-state PRs for EPUB namespace/prefix/metadata namespace; no matching fix found. Prepared with AI assistance. Community review does not clear the maintainer merge gate.

[Alex (ac1982)]

@microsoft-github-policy-service agree

[PRABHU KIRAN VANDRANKI (VANDRANKI)]

This is a community review. It does not clear the merge gate.

The prefix handling is a real improvement, but I found a regression for EPUBs that use a namespace other than the current EPUB 2/3 ones. Details below. I ran everything on Windows with Python 3.13, PR head against main 4cc9fa1.

What works (ran):

• The three new parametrized tests in test_epub.py fail on main (3 failed, 8 passed) and pass on the PR. tests/test_epub.py on the PR: 11 passed. Filtering the whole test directory with -k epub on the PR: 12 passed.
• I did not run the full suite, and I did not run it against a real-world EPUB that uses prefixed OPF elements.

Regression I reproduced. The old code used getElementsByTagName("item"), ("itemref") and ("dc:title"), so it matched whatever namespace the file declared. The new _get_elements first asks for the exact namespace and only falls back to elements with namespaceURI is None. An element that has a different non-empty namespace matches neither. I built minimal archives with one chapter and a dc:title/dc:creator:

input	main	PR
standard EPUB 2/3 namespaces	title, author, chapter all found	same
container.xml with no namespace	all found	all found
OPF default namespace http://openebook.org/namespaces/oeb-package/1.0/ (the OEB 1.2 package namespace)	all found	title and author found, chapter text missing
xmlns:dc="http://purl.org/dc/elements/1.0/"	title and author found	title None, author missing
xmlns:dc="http://purl.org/dc/elements/1.1" (no trailing slash)	title and author found	title None, author missing

The first of those is the worst outcome: the conversion succeeds with an empty body, which is the same silent loss this PR is trying to fix for prefixed elements. I do not know how common these files are. OEB 1.2 predates EPUB 2, so I expect them to be rare. The trailing-slash variant is a malformed file, but main tolerated it. If you want to keep the old leniency, one option is to fall back to matching on localName when the namespace lookup finds nothing, instead of only when namespaceURI is None. I have not tried that change.

Smaller notes:

• The new test is placed after the if __name__ == "__main__": raise SystemExit(pytest.main([__file__])) block. Under pytest it is collected fine (I confirmed that), but running the file directly would exit before it is defined.
• In _get_all_texts_from_nodes, tag_name.removeprefix("dc:") hardwires every caller to the Dublin Core namespace. I checked that the existing callers in convert only pass dc: tags; I did not audit anything outside this file.

[Alex (ac1982)]

Thanks for the concrete compatibility cases. I reproduced the OEB 1.2 and both Dublin Core failures, plus an alternate container URI, at the previous PR head (4 failed, 11 passed). The fallback now uses the original tag names when standard-namespace matching finds nothing, preserving the old tolerance while retaining arbitrary-prefix support for standard namespaces.

Added six compatibility cases including the two unnamespaced controls, and moved the direct-test entry point to the end. All 17 EPUB tests pass, including direct file execution. The text helper only serves the existing Dublin Core callers.

Full suite: 1103 passed, 12 skipped, one failure for a missing local FLAC executable. After installing FLAC, that test and the EPUB file passed together (18 passed). Black and diff checks pass. I updated the PR description with those exact results and the remaining platform/real-file limits.