Function _make_annotate_function

Lib/dataclasses.py:536–576

(__class__, method_name, annotation_fields, return_type)

def _make_annotate_function(__class__, method_name, annotation_fields, return_type):
    # Create an __annotate__ function for a dataclass
    # Try to return annotations in the same format as they would be
    # from a regular __init__ function

    def __annotate__(format, /):
        Format = annotationlib.Format
        match format:
            case Format.VALUE | Format.FORWARDREF | Format.STRING:
                cls_annotations = {}
                for base in reversed(__class__.__mro__):
                    cls_annotations.update(
                        annotationlib.get_annotations(base, format=format)
                    )

                new_annotations = {}
                for k in annotation_fields:
                    # gh-142214: The annotation may be missing in unusual dynamic cases.
                    # If so, just skip it.
                    try:
                        new_annotations[k] = cls_annotations[k]
                    except KeyError:
                        pass

                if return_type is not MISSING:
                    if format == Format.STRING:
                        new_annotations["return"] = annotationlib.type_repr(return_type)
                    else:
                        new_annotations["return"] = return_type

                return new_annotations

            case _:
                raise NotImplementedError(format)

    # This is a flag for _add_slots to know it needs to regenerate this method
    # In order to remove references to the original class when it is replaced
    __annotate__.__generated_by_dataclasses__ = True
    __annotate__.__qualname__ = f"{__class__.__qualname__}.{method_name}.__annotate__"

    return __annotate__


def _field_assign(frozen, name, value, self_name):