UuidRegistry.clear_custom_registrations() does not restore SIG name aliases shadowed by a runtime registration

[RonanB96]

Summary

UuidRegistry.clear_custom_registrations() permanently corrupts the registry when a custom characteristic (or service) is registered under a name that aliases an existing SIG entry but with a different UUID. After the custom registration is cleared, the SIG name alias is lost and never restored, so subsequent name lookups return None.

Reproduction

from bluetooth_sig.gatt.uuid_registry import get_uuid_registry
from bluetooth_sig.gatt.characteristics.custom import CustomBaseCharacteristic
from bluetooth_sig.types import CharacteristicInfo
from bluetooth_sig.types.uuid import BluetoothUUID

reg = get_uuid_registry()
assert reg.get_characteristic_info("Temperature") is not None  # SIG 2A6E

class TemperatureCharacteristic(CustomBaseCharacteristic):
    _info = CharacteristicInfo(
        uuid=BluetoothUUID("AA112A6E-0000-1000-8000-00805F9B34FB"),  # custom UUID
        name="Temperature",                                          # SIG name
        unit="C", python_type=float,
    )
    def _decode_value(self, data, ctx=None, *, validate=True): return 0.0
    def _encode_value(self, data): return bytearray([0, 0])

TemperatureCharacteristic()                       # auto-registers
get_uuid_registry().clear_custom_registrations()

print(reg.get_characteristic_info("Temperature")) # -> None  (BUG: should be SIG 2A6E)

Root cause

• register_characteristic() stores the custom info and, via _store_characteristic() / _generate_aliases(), writes the name alias "temperature" -> <custom canonical UUID>, overwriting the SIG mapping "temperature" -> 2A6E.
• The SIG-entry preservation machinery (_characteristic_overrides) only triggers on a canonical UUID conflict (canonical_key in self._characteristics). A same-name/different-UUID registration is not a canonical conflict, so nothing is preserved.
• clear_custom_registrations() deletes aliases whose canonical target is a runtime UUID (correctly removing the custom "temperature" alias) but has no record of the SIG alias it shadowed, so it cannot restore "temperature" -> 2A6E. The SIG canonical entry still exists; only the alias is gone.

Impact

• Any register -> clear cycle of a name-colliding custom characteristic/service leaves the SIG registry with a missing name alias for the rest of the process.
• In the test suite this manifests as cross-test pollution: tests/registry/test_registry_validation.py::TestNameResolutionFallback registers custom chars named "Temperature" and "Model Number String", which then breaks later tests that look those names up:
  • tests/registry/test_yaml_units.py::TestYAMLUnitParsing::test_yaml_unit_loading_basic
  • tests/static_analysis/test_characteristic_registry_completeness.py::TestCharacteristicEnumCompleteness::test_all_sig_characteristics_have_enum_entries
  • tests/static_analysis/test_characteristic_registry_completeness.py::TestCharacteristicEnumCompleteness::test_characteristic_enum_names_match_yaml

This regression was introduced when custom auto-registration began writing custom info (including the name alias) into the global uuid_registry via RegistrationManager (previously the translator path did not touch the uuid_registry alias index).

Current workaround

The polluting fallback tests instantiate their inline custom characteristics with auto_register=False so they don't write to the global uuid_registry. This keeps the suite green but does not fix the underlying registry defect.

Proposed fix

Make alias handling symmetric with canonical-entry handling. Rebuild the alias indices from the canonical stores at the end of clear_custom_registrations() (aliases are fully derivable from canonical infos), e.g.:

def _rebuild_aliases(self) -> None:
    self._service_aliases.clear()
    self._characteristic_aliases.clear()
    self._descriptor_aliases.clear()
    for info in self._services.values():
        for alias in self._generate_aliases(info):
            self._service_aliases[alias.lower()] = info.uuid.normalized
    for info in self._characteristics.values():
        for alias in self._generate_aliases(info):
            self._characteristic_aliases[alias.lower()] = info.uuid.normalized
    for info in self._descriptors.values():
        for alias in self._generate_aliases(info):
            self._descriptor_aliases[alias.lower()] = info.uuid.normalized

Alternatively, preserve overwritten aliases at registration time and restore them on clear.

Acceptance criteria

• The reproduction above returns the SIG Temperature info after clear.
• Registering then clearing a custom service/characteristic/descriptor with a SIG-colliding name leaves all SIG name aliases intact.
• The auto_register=False workaround can be removed from tests/registry/test_registry_validation.py::TestNameResolutionFallback and the full suite still passes in a single process.