Function analyze_param

fastapi/dependencies/utils.py:393–559

(
    *,
    param_name: str,
    annotation: Any,
    value: Any,
    is_path_param: bool,
)

def analyze_param(
    *,
    param_name: str,
    annotation: Any,
    value: Any,
    is_path_param: bool,
) -> ParamDetails:
    field_info = None
    depends = None
    type_annotation: Any = Any
    use_annotation: Any = Any
    if is_typealiastype(annotation):
        # unpack in case PEP 695 type syntax is used
        annotation = annotation.__value__
    if annotation is not inspect.Signature.empty:
        use_annotation = annotation
        type_annotation = annotation
    # Extract Annotated info
    if get_origin(use_annotation) is Annotated:
        annotated_args = get_args(annotation)
        type_annotation = annotated_args[0]
        fastapi_annotations = [
            arg
            for arg in annotated_args[1:]
            if isinstance(arg, (FieldInfo, params.Depends))
        ]
        fastapi_specific_annotations = [
            arg
            for arg in fastapi_annotations
            if isinstance(
                arg,
                (
                    params.Param,
                    params.Body,
                    params.Depends,
                ),
            )
        ]
        if fastapi_specific_annotations:
            fastapi_annotation: FieldInfo | params.Depends | None = (
                fastapi_specific_annotations[-1]
            )
        else:
            fastapi_annotation = None
        # Set default for Annotated FieldInfo
        if isinstance(fastapi_annotation, FieldInfo):
            # Copy `field_info` because we mutate `field_info.default` below.
            field_info = copy_field_info(
                field_info=fastapi_annotation,
                annotation=use_annotation,
            )
            assert (
                field_info.default == Undefined or field_info.default == RequiredParam
            ), (
                f"`{field_info.__class__.__name__}` default value cannot be set in"
                f" `Annotated` for {param_name!r}. Set the default value with `=` instead."
            )
            if value is not inspect.Signature.empty: