Running `get_dynamic_class_hook()` after `get_class_decorator_hook_2()`

Feature

It would be useful to run get_dynamic_class_hook() from plugins after get_class_decorator_hook_2() to support dynamic classes that inspect existing dataclasses / attrs classes.

Pitch

We have an internal mypy plugin that makes "partial" classes, where all required attributes are optional. It does this by examining the __init__ of an attrs class and creating a new __init__ for the new class where all args are now optional. This works in mypy 0.942, occasionally crashes in 0.950, and doesn't work at all in 0.960 (128661ccbf4396ed1538421c481f1773c7490169) because the attrs __init__ is not present during get_dynamic_class_hook().

Is there some way to work around this?

まず、プラグインのエントリポイントである get_dynamic_class_hook() と get_class_decorator_hook_2() をたどり、フックの順序によって attrs が生成した init メソッドがどのように公開されるかを確認します。動的クラスフックがデコレータ処理後の既存の dataclasses または attrs クラスを検査でき、ここで説明されている partial-class プラグインのシナリオに対する回帰テストのカバレッジが追加されたら、この変更は完了です。