Do not retry numeric-only getaddrinfo failures

[Cherith1222]

Summary

trio.socket.getaddrinfo retried a numeric lookup in a worker thread, or called the custom hostname resolver, after the non-blocking attempt failed with EAI_NONAME. When the caller already passed AI_NUMERICHOST|AI_NUMERICSERV, that retry is the same lookup. The EAI_NONAME error is now raised directly.

Fixes #1249.

newsfragments/1249.bugfix.rst is in the commit.

Test Plan

On Windows, Python 3.13, PYTHONPATH=src:

• pytest src/trio/_tests/test_socket.py -k "numeric_only_flags or custom_hostname_resolver or idna" -p no:cacheprovider -q → before the change, 1 failed and 2 passed; after, 3 passed.
• The whole src/trio/_tests/test_socket.py → 31 passed, 4 skipped (Linux-only, two --run-slow tests, and no Unix domain socket).

Not run: slow tests, the rest of the suite, the type check, and non-Windows platforms.

AI assistance

Drafted with Cursor. The account owner authorized opening this pull request. Cherith reviewed this diff and confirmed it with the person who helped draft it. There is no Co-authored-by, Reviewed-by, or Signed-off-by trailer.

[codecov]

Codecov Report

❌ Patch coverage is 91.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 99.99487%. Comparing base (bcc9cee) to head (80343b2).

Files with missing lines	Patch %	Lines
src/trio/_tests/test_socket.py	91.66667%	1 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                  @@
##                 main       #3535         +/-   ##
====================================================
- Coverage   100.00000%   99.99487%   -0.00513%     
====================================================
  Files             128         128                 
  Lines           19474       19485         +11     
  Branches         1323        1323                 
====================================================
+ Hits            19474       19484         +10     
- Misses              0           1          +1     

Files with missing lines	Coverage Δ
src/trio/_socket.py	100.00000% <ø> (ø)
src/trio/_tests/test_socket.py	99.84663% <91.66667%> (-0.15337%)	⬇️

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