IPv6Address.exploded raises AddressValueError for valid scoped addresses

[augusto-rehfeldt]

Bug report

Bug description:

Documented behaviour: The inherited exploded property in _IPAddressBase promises: "Return the longhand version of the IP address as a string." The IPv6Address documentation permits a scope zone ID appended using '%', giving 'ff02::1234%1' as an example.

Expected: fe80:0000:0000:0000:0000:0000:0000:0001%a

Actual: AddressValueError: Only hex digits permitted in '1%a' in 'fe80::1%a'

import ipaddress

s = 'fe80::1%' + 'a'
try:
    zone = s.split('%')[1]
    if not zone or not zone.isascii() or not zone.isalpha():
        raise ValueError('scope is not nonempty ASCII alphabetic')
    a = ipaddress.IPv6Address(s)
    n = 0xfe800000000000000000000000000001
    if a.scope_id != zone or int(a) != n:
        raise ValueError('input did not parse as the documented scoped address')
except Exception as e:
    print('REFUTATION REJECTED:', str(e))
else:
    expected = ':'.join(f'{(n >> i) & 65535:04x}' for i in range(112, -1, -16)) + '%' + zone
    try:
        actual = a.exploded
    except Exception as e:
        actual = (type(e).__name__, str(e))
    if actual != expected:
        print('REFUTATION CONFIRMED:', repr(s), 'actual =', repr(actual), 'expected =', repr(expected))
    else:
        print('REFUTATION REJECTED: exploded matches the documented expectation')

Output on Python 3.14.6 (Windows-11-10.0.26220-SP0), standard library ipaddress:

REFUTATION CONFIRMED: 'fe80::1%a' actual = ('AddressValueError', "Only hex digits permitted in '1%a' in 'fe80::1%a'") expected = 'fe80:0000:0000:0000:0000:0000:0000:0001%a'

This report was found and written by an automated property-testing tool I run (bugforge). The reproducer above was executed and its output is pasted unedited; no person reviewed the report before it was filed. The search script is in https://github.com/augusto-rehfeldt/bugforge-results/tree/main/ipaddress-c1

CPython versions tested on:

3.14

Operating systems tested on:

Windows

[ZeroIntensity]

See #158748 (comment).