define.classful

class_signature(cls)

Constructs a inspect.Signature object for a type. It uses the class-level annotations as the parameters so that we can treat the classes and functions the same

Source code in /home/sean/sourcecode/arc/arc/define/classful.py

def class_signature(cls: type) -> inspect.Signature:
    """Constructs a `inspect.Signature` object for a type.
    It uses the class-level annotations as the parameters so
    that we can treat the classes and functions the same
    """
    annotations = t.get_type_hints(cls, include_extras=True)
    defaults = {name: getattr(cls, name) for name in dir(cls) if not isdunder(name)}
    attrs = {}

    for name, annotation in annotations.items():
        attrs[name] = (annotation, inspect.Parameter.empty)

    for name, default in defaults.items():
        if inspect.isfunction(default):
            continue

        if name in attrs:
            attrs[name] = (attrs[name][0], default)
        else:
            attrs[name] = (t.Any, default)

    parameters = [
        inspect.Parameter(
            name=name,
            kind=inspect.Parameter.POSITIONAL_OR_KEYWORD,
            default=default,
            annotation=annotation,
        )
        for name, (annotation, default) in attrs.items()
    ]

    sig = inspect.Signature(
        sorted(parameters, key=lambda p: not p.default is inspect.Parameter.empty)
    )
    # inspect.signature() checks for a cached signature object
    # at __signature__. So we can cache it there
    # to generate the correct signature object
    # during the parameter building process
    setattr(cls, "__signature__", sig)
    return sig