Method _check_param

nonebot/internal/params.py:206–242

(
        cls, param: inspect.Parameter, allow_types: tuple[type[Param], ...]
    )

    @classmethod
    @override
    def _check_param(
        cls, param: inspect.Parameter, allow_types: tuple[type[Param], ...]
    ) -> Self | None:
        type_annotation, depends_inner = param.annotation, None
        # extract type annotation and dependency from Annotated
        if get_origin(param.annotation) is Annotated:
            type_annotation, *extra_args = get_args(param.annotation)
            depends_inner = next(
                (x for x in reversed(extra_args) if isinstance(x, DependsInner)), None
            )

        # param default value takes higher priority
        depends_inner = (
            param.default if isinstance(param.default, DependsInner) else depends_inner
        )
        # not a dependent
        if depends_inner is None:
            return

        dependency: T_Handler
        # sub dependency is not specified, use type annotation
        if depends_inner.dependency is None:
            assert type_annotation is not inspect.Signature.empty, (
                "Dependency cannot be empty"
            )
            dependency = type_annotation
        else:
            dependency = depends_inner.dependency
        # parse sub dependency
        sub_dependent = Dependent[Any].parse(
            call=dependency,
            allow_types=allow_types,
        )

        return cls._from_field(
            sub_dependent, depends_inner.use_cache, depends_inner.validate
        )

    @classmethod
    @override