BaseRequest.text() and .post(): map invalid body bytes to HTTP 415

[HrachShah]

Fixes #13099.

BaseRequest.text() and the application/x-www-form-urlencoded branch of BaseRequest.post() catch LookupError from bytes.decode(charset) and re-raise it as HTTPUnsupportedMediaType (HTTP 415). The intent is to surface any decode problem as a 415 so the user gets a clear status code instead of an unhandled UnicodeDecodeError in their handler.

But the catch only covers LookupError, which is what an unknown codec raises (LookupError: unknown encoding: ...). It misses the more common case: the charset name is known (utf-8, latin-1, etc.) but the body is not valid in that encoding. bytes.decode() raises UnicodeDecodeError for that, which is a subclass of ValueError, so it propagates out of text() / post() and crashes the handler with a traceback that the user has no way to handle cleanly.

Fix: extend the except clause to also catch UnicodeDecodeError, so an invalid byte sequence in the body maps to the same HTTP 415 a missing codec does. The body is still consumed and the existing _read_bytes cache is populated, so subsequent req.read() / req.json() calls don't re-decode.

Tests in tests/test_web_request.py:

• test_request_text_raises_415_for_invalid_utf8_bytes — req.text() with body b'\xff' and Content-Type: text/plain; charset=utf-8 now raises HTTPUnsupportedMediaType (pre-fix: leaks UnicodeDecodeError).
• test_request_post_urlencoded_raises_415_for_invalid_utf8_bytes — req.post() with body b'a=1&b=\xff' and Content-Type: application/x-www-form-urlencoded now raises HTTPUnsupportedMediaType (pre-fix: leaks UnicodeDecodeError).

Both tests fail on the pre-fix code with the original UnicodeDecodeError and pass with the fix applied.

$ PYTHONPATH='.' python3 -m pytest tests/test_web_request.py -k 'invalid_utf8 or wrong_content_type' -v
============================== 3 passed in 0.09s ==============================

Full tests/test_web_request.py run: 135 passed.

CHANGES fragment at CHANGES/13099.bugfix.rst.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.97%. Comparing base (9e00085) to head (953471e).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #13100   +/-   ##
=======================================
  Coverage   98.97%   98.97%           
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  Files         131      131           
  Lines       48635    48652   +17     
  Branches     2525     2525           
=======================================
+ Hits        48135    48154   +19     
+ Misses        376      374    -2     
  Partials      124      124           

Flag	Coverage Δ
Autobahn	22.12% <10.52%> (-0.01%)	⬇️
CI-GHA	98.92% <100.00%> (+<0.01%)	⬆️
OS-Linux	98.68% <100.00%> (+<0.01%)	⬆️
OS-Windows	97.08% <100.00%> (+<0.01%)	⬆️
OS-macOS	97.97% <100.00%> (+<0.01%)	⬆️
Py-3.10	98.16% <100.00%> (+<0.01%)	⬆️
Py-3.11	98.43% <100.00%> (+<0.01%)	⬆️
Py-3.12	98.52% <100.00%> (+<0.01%)	⬆️
Py-3.13	98.49% <100.00%> (+0.01%)	⬆️
Py-3.14	98.51% <100.00%> (+<0.01%)	⬆️
Py-3.14t	97.61% <100.00%> (+<0.01%)	⬆️
Py-pypy-3.11	97.47% <100.00%> (-0.01%)	⬇️
VM-macos	97.97% <100.00%> (+<0.01%)	⬆️
VM-ubuntu	98.68% <100.00%> (+<0.01%)	⬆️
VM-windows	97.08% <100.00%> (+<0.01%)	⬆️
cython-coverage	37.91% <0.00%> (-0.02%)	⬇️

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[codspeed-hq]

Merging this PR will not alter performance

✅ 83 untouched benchmarks
⏩ 83 skipped benchmarks¹

---

_{Comparing HrachShah:fix/13099-text-unicodedecode-as-415 (953471e) with master (9e00085)}

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. ↩