Function fields

src/msgspec/structs.py:64–114

Get information about the fields in a Struct. Parameters ---------- type_or_instance: A struct type or instance. Returns ------- tuple[FieldInfo]

(type_or_instance: Struct | type[Struct])

def fields(type_or_instance: Struct | type[Struct]) -> tuple[FieldInfo]:
    """Get information about the fields in a Struct.

    Parameters
    ----------
    type_or_instance:
        A struct type or instance.

    Returns
    -------
    tuple[FieldInfo]
    """
    obj = type_or_instance

    # Struct class
    if isinstance(obj, StructMeta):
        annotated_cls = cls = obj
    # Struct instance
    elif isinstance(type(obj), StructMeta):
        annotated_cls = cls = type(obj)
    # Generic alias
    else:
        annotated_cls = obj
        cls = getattr(obj, "__origin__", obj)
        if not isinstance(cls, StructMeta):
            raise TypeError("Must be called with a struct type or instance")

    hints = _get_class_annotations(annotated_cls)
    npos = len(cls.__struct_fields__) - len(cls.__struct_defaults__)
    fields = []
    for name, encode_name, default_obj in zip(
        cls.__struct_fields__,
        cls.__struct_encode_fields__,
        (NODEFAULT,) * npos + cls.__struct_defaults__,
    ):
        default = default_factory = NODEFAULT
        if isinstance(default_obj, _Factory):
            default_factory = default_obj.factory
        elif default_obj is not NODEFAULT:
            default = default_obj

        field = FieldInfo(
            name=name,
            encode_name=encode_name,
            type=hints[name],
            default=default,
            default_factory=default_factory,
        )
        fields.append(field)

    return tuple(fields)