fix(file): match extension accept specifiers by filename

[Kiarokh]

What

fix #4183
limel-file-dropzone filters dropped files with isTypeAccepted (src/util/files.ts). For a .ext accept specifier it matched against the file's MIME subtype (contentType.endsWith('/ext')), not the filename:

if (acceptedType.startsWith('.')) {
    const fileType = acceptedType.split('.')[1]; // ".docx" -> "docx"
    return file.contentType.endsWith(`/${fileType}`);
}

That only works when the subtype happens to equal the extension (.pdf → application/pdf, .csv → text/csv). Files whose subtype differs were silently rejected on drag-and-drop — e.g. all Office/iWork/OpenDocument formats, .txt (text/plain), .eml/.msg, and most archives (.7z, .rar, .tar, .gz, …). The file chooser was unaffected, because the browser matches accept by filename. split('.')[1] also meant multi-part extensions like .tar.gz never matched.

Change

Match .ext specifiers against the filename (case-insensitively), the way the native accept attribute does. MIME specifiers (type/subtype and type/*) still match contentType and are unchanged.

Tests

src/util/files.spec.ts: the existing describe.each files now carry a filename (which keeps every existing expectation valid), plus a new block covering the fix — an extension whose MIME subtype differs (.docx), multi-part extensions (.tar.gz), case-insensitivity, an unhelpful content type (application/octet-stream), and matching within a comma-separated list. All spec tests pass.

Out of scope (follow-up)

limel-file only wires the dropzone's filesSelected, not filesRejected, so a genuinely-unsupported dropped file is still silently ignored (no upload, no feedback). Surfacing that needs a small UX/API decision and is left as a follow-up — see the issue.

Refs #4183

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Improved file type validation for extension-based accept rules.
  • Added support for case-insensitive filename matching, multi-part extensions, and comma-separated accept lists.
  • Fixed handling of document extensions such as .docx.
  • Improved validation when the content type is unavailable or unreliable.

[coderabbitai]

📝 Walkthrough

Walkthrough

isTypeAccepted now matches extension-based accept specifiers against the filename, including case-insensitive and multipart suffixes. Tests update existing cases with filenames and add regression coverage for mismatches, unhelpful MIME types, and accept lists.

Changes

Filename extension acceptance

Layer / File(s)	Summary
Filename matching and regression coverage src/util/files.ts, src/util/files.spec.ts	Extension specifiers are checked against file.filename using a case-insensitive suffix comparison. Tests cover matching, mismatches, .docx, multipart extensions, case differences, unhelpful content types, and comma-separated accept lists.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related issues

• Issue 4183: The change addresses its filename-based extension matching objective in isTypeAccepted.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and accurately summarizes the main change: matching extension accept specifiers by filename.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/file-accept-extension-matching

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[github-actions]

Documentation has been published to https://lundalogik.github.io/lime-elements/versions/PR-4184/

[lime-opensource]

🎉 This PR is included in version 39.44.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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