Allow ABCMeta in PyType_FromMetaclass

Feature or enhancement

Proposal:

Currently Python 3.14 will deny any metaclass that implements tp_new, which ABCMeta does.

My suggestion is to add special logic in PyType_FromMetaclass that if the metaclass is ABCMeta or a subtype uses its tp_new instead of custom that it adds the abstract flag, and calls the method that calculates abstractmethods attribute.

Currently there is logic in CPython to mark native methods as abstract.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

まず、PyType_FromMetaclass と、ネイティブメソッドを抽象としてマークする既存のロジックを特定します。ABCMeta とそのサブタイプが tp_new をどのように処理し、abstractmethods がどのように計算されるかを追跡します。ABCMeta 互換のメタクラスが受け入れられ、抽象フラグと計算の動作が維持されれば完了です。