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Recursive conversion for msgspec
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| from typing import Any, Final | |
| import msgspec | |
| from msgspec import inspect | |
| class _RecurseMarker: | |
| def __repr__(self): | |
| return "RECURSE" | |
| RECURSE: Any = _RecurseMarker() | |
| """Initialize nested struct from parent fields. Use with | |
| ``convert_recursive()``.""" | |
| COMPOSITE_TYPES: Final = (inspect.StructType, inspect.DataclassType) | |
| def convert_recursive(obj, type, *, from_attributes=True): | |
| """ | |
| Convert the input object to the specified type, or error accordingly. | |
| Recurses into nested structs if default=RECURSE is set. | |
| """ | |
| it = msgspec.convert(obj, type, from_attributes=from_attributes) | |
| type_info = inspect.type_info(type) | |
| if not isinstance(type_info, COMPOSITE_TYPES): | |
| return it | |
| for fld in type_info.fields: | |
| if fld.default is not RECURSE: | |
| continue | |
| if isinstance(fld.type, COMPOSITE_TYPES): | |
| value = convert_recursive( | |
| obj, | |
| fld.type.cls, | |
| from_attributes=from_attributes, | |
| ) | |
| else: | |
| raise TypeError("RECURSE fields must be structs or dataclasses") | |
| setattr(it, fld.name, value) | |
| return it | |
| # Example: | |
| if __name__ == "__main__": | |
| class ServiceSpec(msgspec.Struct): | |
| name: str | |
| labels: dict[str, str] | |
| image: str | |
| environment: list[str] | |
| class DockerContainerSpec(msgspec.Struct): | |
| image: str = msgspec.field(name="Image") | |
| environment: list[str] = msgspec.field(name="Env") | |
| class DockerTaskTemplate(msgspec.Struct): | |
| _container_spec: DockerContainerSpec = msgspec.field(default=RECURSE, name="ContainerSpec") | |
| class DockerService(msgspec.Struct): | |
| name: str = msgspec.field(name="Name") | |
| labels: dict[str, str] = msgspec.field(name="Labels") | |
| _task_template: DockerTaskTemplate = msgspec.field(default=RECURSE, name="TaskTemplate") | |
| assert msgspec.json.encode( | |
| convert_recursive( | |
| ServiceSpec( | |
| name="test", | |
| labels={}, | |
| image="nginx:alpine", | |
| environment=["HELLO=world"], | |
| ), | |
| type=DockerService | |
| ) | |
| ) == ( | |
| b'{"Name":"test","Labels":{},"TaskTemplate":{' | |
| b'"ContainerSpec":{"Image":"nginx:alpine","Env":["HELLO=world"]}}}' | |
| ) |
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