[pcbeingused333]

The ipv6 format rejects valid addresses that have exactly one group before :: and six groups after it (counting an IPv4 tail as two):

>>> import fastjsonschema
>>> v = fastjsonschema.compile({"type": "string", "format": "ipv6"})
>>> v("1::2:3:4:5:6")
fastjsonschema.exceptions.JsonSchemaValueException: data must be ipv6
>>> v("1::2:3:4:1.2.3.4")
fastjsonschema.exceptions.JsonSchemaValueException: data must be ipv6
>>> import ipaddress; ipaddress.IPv6Address("1::2:3:4:5:6")
IPv6Address('1::2:3:4:5:6')

In draft04.py, the regex alternative for "up to two groups before ::" is (?:h:h)?::(?:h:){3}..., which allows exactly two groups or none. The other alternatives use (?:(?:h:){,n}h)?. This PR uses the same form here ({,1}).

The current JSON-Schema-Test-Suite has a case for this: optional/format/ipv6.json, "one group before '::' and five groups after is valid". The suite pinned in this repo (Test-JSON-Schema-Acceptance-1.026) is older and doesn't include it.

Tests

• tests/test_format.py::test_ipv6: added 1::2:3:4:5:6 and 1::2:3:4:1.2.3.4 (valid), plus 1::2:3:4:5:6:7:8 (invalid, too many groups). The two valid cases fail on master and pass with this change.
• Every address shape was compared with ipaddress.IPv6Address: 0–8 groups before and after ::, with and without an IPv4 tail, plus the fully written-out forms.
  • Master: 2 mismatches (1::10:11:12:13:14 and 1::10:11:12:1.2.3.4).
  • This branch: none.
• pytest tests with the pinned suite: 4512 passed, 449 xfailed, 936 xpassed. The 12 errors are in tests/benchmarks, which need pytest-benchmark (not installed in that run).
• pylint fastjsonschema: no new warnings.

This change was written with an AI coding assistant (Claude Code).

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