cadrumo.core.frozen_mapping module

A read-only mapping that frozen models can share across consumers.

A frozen pydantic model refuses attribute assignment, but a Mapping field still validates to a plain dict that any holder can mutate in place. That single hole is what forces a model graph to be rebuilt per consumer. FROZEN_MAPPING closes it at the defining field: annotate Annotated[Mapping[K, V], FROZEN_MAPPING] and the validated value is a FrozenMapping, while construction still accepts any mapping and serialisation still emits the same JSON object the dict did.

class FrozenMapping(items)

Bases: Mapping, Generic

An immutable mapping whose copy, shallow or deep, is itself.

Sharing by copy is correct only because nothing reachable through the mapping can change: it has no mutating methods, its storage is a read-only proxy, and FROZEN_MAPPING is applied only to fields whose values are themselves frozen. A deep copy of a model holding one therefore shares the mapping instead of failing on it, which a bare MappingProxyType does.

Parameters:

items (Mapping[K, V])

class FrozenMappingMarker

Bases: object

Pydantic annotation that validates a mapping field into a FrozenMapping.