1from collections.abc import Callable
 2from importlib import import_module
 3from typing import Any, overload
 4
 5
 6@overload
 7def deconstructible[T](cls: type[T], /) -> type[T]: ...
 8@overload
 9def deconstructible[T](*, path: str | None = ...) -> Callable[[type[T]], type[T]]: ...
10def deconstructible[T](
11    *args: type[T], path: str | None = None
12) -> Callable[[type[T]], type[T]] | type[T]:
13    """
14    Class decorator that allows the decorated class to be serialized
15    by the migrations subsystem.
16
17    The `path` kwarg specifies the import path.
18    """
19
20    def decorator(klass: type[T]) -> type[T]:
21        def __new__(cls: type[T], *args: Any, **kwargs: Any) -> T:
22            # We capture the arguments to make returning them trivial
23            obj = super(klass, cls).__new__(cls)  # ty: ignore[unresolved-attribute]
24            obj._constructor_args = (args, kwargs)
25            return obj
26
27        def deconstruct(obj: Any) -> tuple[str, tuple[Any, ...], dict[str, Any]]:
28            """
29            Return a 3-tuple of class import path, positional arguments,
30            and keyword arguments.
31            """
32            # Fallback version
33            if path and type(obj) is klass:
34                module_name, _, name = path.rpartition(".")
35            else:
36                module_name = obj.__module__
37                name = obj.__class__.__name__
38            # Make sure it's actually there and not an inner class
39            module = import_module(module_name)
40            if not hasattr(module, name):
41                raise ValueError(
42                    f"Could not find object {name} in {module_name}.\n"
43                    "Please note that you cannot serialize things like inner "
44                    "classes. Please move the object into the main module "
45                    "body to use migrations."
46                )
47            return (
48                path
49                if path and type(obj) is klass
50                else f"{obj.__class__.__module__}.{name}",
51                obj._constructor_args[0],
52                obj._constructor_args[1],
53            )
54
55        setattr(klass, "__new__", staticmethod(__new__))
56        setattr(klass, "deconstruct", deconstruct)
57
58        return klass
59
60    if not args:
61        return decorator
62    return decorator(*args)