fix: DTO factory narrowed with a generic alias. #2791
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peterschutt
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This PR is an attempt at handling DTOs that are narrowed with a `_GenericAlias` of a type supported by the DTO factory type. Closes #2500
peterschutt
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| @@ -110,7 +111,7 @@ def __init__( | |||
| rename_fields=self.dto_factory.config.rename_fields, | |||
| ) | |||
| self.transfer_model_type = self.create_transfer_model_type( | |||
| model_name=model_type.__name__, field_definitions=self.parsed_field_definitions | |||
| model_name=(get_origin(model_type) or model_type).__name__, field_definitions=self.parsed_field_definitions | |||
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With this feature, anywhere that we could previously assume that the type that narrowed the dto was just a regular class, we now have to account for the fact that it could be an instance of _GenericAlias.
In the my first pass of this PR I've taken the quickest and dirtiest approach to get things passing, but we might need some abstraction over the type that handles the differences.
| @@ -29,7 +31,8 @@ class DataclassDTO(AbstractDTO[T], Generic[T]): | |||
| def generate_field_definitions( | |||
| cls, model_type: type[DataclassProtocol] | |||
| ) -> Generator[DTOFieldDefinition, None, None]: | |||
| dc_fields = {f.name: f for f in fields(model_type)} | |||
| model_origin = get_origin(model_type) or model_type | |||
| dc_fields = {f.name: f for f in fields(model_origin)} | |||
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We'll have to test this against all of the other dto factory types that support generics too, b/c there is bound to be cases where the _GenericAlias instances break things in there too.
| if isinstance(self.annotation, _GenericAlias) and self.origin not in (ClassVar, Literal): | ||
| cl_args = get_args(cl) | ||
| cl_origin = get_origin(cl) or cl | ||
| return ( | ||
| issubclass(self.origin, cl_origin) | ||
| and (len(cl_args) == len(self.args) if cl_args else True) | ||
| and ( | ||
| all(t.is_subclass_of(cl_arg) for t, cl_arg in zip(self.inner_types, cl_args)) | ||
| if cl_args | ||
| else True | ||
| ) | ||
| ) | ||
|
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Trying to determine when a _GenericAlias type should be considered a sub-type of another type.
This says that when A is a _GenericAlias instance, then it is a subclass of B when:
- if
Bis parametrized, thenAs origin is a subtype ofBs origin, otherwiseA's origin is a subtype ofB. - if
Bis parametrized, thenAandBmust have the same number of type parameters declared - if
Bis parametrized, thenAs type params are pairwise subtypes ofBs type params
With 2 and 3, if B is not parametrized, and origin of A is a subtype of B then I think we should treat that as B[Any, ...] so the type parameters only come into it if both types have args declared.
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I'll have to add a lot of tests for this.
| if not (parameters := getattr(annotation, "__parameters__", None)): | ||
| return type_hints | ||
| typevar_map = {p: p for p in parameters} |
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This is to support using this function without knowing up front if the type we are passing in is a generic type or not. If not, it won't have the parameters attribute, and so we just return the type hints without any post processing.
| @@ -161,3 +163,28 @@ class SubType(Model): | |||
| assert ( | |||
| dto_type._dto_backends["handler_id"]["data_backend"].parsed_field_definitions[-1].name == "c" # pyright: ignore | |||
| ) | |||
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| def test_type_narrowing_with_generic_type() -> None: | |||
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should name it test_get_model_type_hints_with_generic_type()
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Kudos, SonarCloud Quality Gate passed! |
|
Documentation preview will be available shortly at https://litestar-org.github.io/litestar-docs-preview/2791 |
Pull Request Checklist
Description
This PR is an attempt at handling DTOs that are narrowed with a
_GenericAliasof a type supported by the DTO factory type.Close Issue(s)
Closes #2500