fix: skip adapter scan for interface lists with no IPv6 entries - #1919

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.87%. Comparing base (bb91be5) to head (ebd5138).

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  Coverage   99.87%   99.87%           
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  Files          33       33           
  Lines        3911     3913    +2     
  Branches      568      568           
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+ Hits         3906     3908    +2     
  Misses          3        3           
  Partials        2        2           

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Merging this PR will not alter performance

✅ 24 untouched benchmarks

_{Comparing skip-adapter-scan-ipv4-list (ebd5138) with master (bb91be5)}

Previous review — superseded by a newer review below.

PR Review — fix: skip adapter scan for interface lists with no IPv6 entries

Ready to merge. Both suggestions from the previous review are fixed at ebd5138, and nothing new came up.

Strengths:

• Single adapter scan. ip6_addresses_to_indexes (src/zeroconf/_utils/net.py:128-145) now works out first which entries need adapters (needs_scan) and returns early when there are none. It then calls ifaddr.get_adapters() from one place only. The adapters = None state and the duplicated guards are gone, as suggested before.
• No behaviour change beyond the fix. Index and IPv6 entries keep their original order and are still handled by the same helpers. An invalid address string still raises ValueError from ipaddress.ip_address, now before the scan instead of after it. That is the same error, just raised sooner.
• Tests cover every path. test_ip6_addresses_to_indexes_scans_once now uses ["192.168.1.5", "2001:db8::", 1, "fd00:db8::"], so an index and an IPv6 address both come after the first scan. It checks that the scan runs exactly once. The empty list and IPv4-only lists are tested both by calling the function directly and through normalize_interface_choice.
• The test docstrings are one line each, as CLAUDE.md asks. _utils/net.py is not Cythonized, so no .pxd change is needed.

Previous findings:

• Suggestion 1 (the lazy-scan guard was repeated): fixed by the needs_scan refactor.
• Suggestion 2 (no test for an IPv6 address after the scan): fixed by the reordered mixed-list test.

✅ Resolved since last review (2)

Checklist

• Correctness: behavior preserved for index/IPv6 entries
• Untested branches introduced by the change
• Structural quality / no duplicated logic
• Edge cases (empty list, IPv4-only list, invalid address)
• No public API or Cython .pxd changes required
• PR description matches diff

Automated review by Kōan (Claude) HEAD=ebd5138 18s

merged after pypi outage clears