parse_mimetype: skip whitespace-only segments after a semicolon

[HrachShah]

What do these changes do?

A trailing semicolon followed by whitespace (e.g. text/html; or text/html;\t) used to be split into a parameter segment that is truthy but contains only whitespace, and parse_mimetype would add it to the parsed parameters dict as {'': ''}. The pre-existing if not item: continue check only handled the case of a bare trailing ;.

The fix changes the check to if not item.strip() so whitespace-only segments are also treated as no-op, matching the RFC 2045 view that there is no parameter — only a delimiter followed by nothing.

The pre-existing application/json; charset=utf-8; test (a real parameter followed by a bare trailing ;) still produces {'charset': 'utf-8'} and is unaffected by this change.

Are there changes in behavior for the user?

Yes. parse_mimetype callers that read parameters via .get('charset') no longer see the spurious empty-key entry {'': ''} from text/html; style inputs. The behaviour for text/html; (a bare trailing semicolon, which was already correctly producing {}) is preserved.

Is it a substantial burden for the maintainers to support this?

No. One-line change in parse_mimetype. No public API changes.

Related issue number

Fixes #13009

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• New feature: a news fragment is added
• CI passes

Drafted with Zo Bot; reviewed by HrachShah.

Drafted with Zo Bot; reviewed by HrachShah.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.96%. Comparing base (e3774b4) to head (5994311).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #13058   +/-   ##
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  Coverage   98.96%   98.96%           
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  Files         131      131           
  Lines       48156    48156           
  Branches     2499     2499           
=======================================
  Hits        47656    47656           
  Misses        376      376           
  Partials      124      124           

Flag	Coverage Δ
Autobahn	22.21% <0.00%> (ø)
CI-GHA	98.90% <100.00%> (ø)
OS-Linux	98.67% <100.00%> (ø)
OS-Windows	97.04% <100.00%> (-0.01%)	⬇️
OS-macOS	97.94% <100.00%> (-0.01%)	⬇️
Py-3.10	98.14% <100.00%> (-0.01%)	⬇️
Py-3.11	98.41% <100.00%> (-0.01%)	⬇️
Py-3.12	98.50% <100.00%> (ø)
Py-3.13	98.47% <100.00%> (-0.01%)	⬇️
Py-3.14	98.50% <100.00%> (+<0.01%)	⬆️
Py-3.14t	97.58% <100.00%> (-0.01%)	⬇️
Py-pypy-3.11	97.45% <100.00%> (ø)
VM-macos	97.94% <100.00%> (-0.01%)	⬇️
VM-ubuntu	98.67% <100.00%> (ø)
VM-windows	97.04% <100.00%> (-0.01%)	⬇️
cython-coverage	38.11% <0.00%> (ø)

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[codspeed-hq]

Merging this PR will not alter performance

✅ 83 untouched benchmarks
⏩ 83 skipped benchmarks¹

---

_{Comparing HrachShah:patch-13009-mimetype (5994311) with master (e3774b4)}

Footnotes

1. 83 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩