Sebastian Berg <[email protected]> added the comment:
Well, what we need is a way to say: I am calling `type.__new__` (i.e.
PyType_FromSpec) on purpose from (effectively) my own `mytype.__new__`?
That is, because right now I assume we want to protect users from calling
PyType_FromSpec thinking that it is equivalent to calling `class new(base)`
when it may not be if base is a metaclass. So calling `PyType_FromSpec` might
refuse to work if it finds a custom `metaclass.__new__` (init?).
I don't really see that it matters if we only support effectively this from C:
```
class MyMetaClass(type):
def __new__(cls, *args, **kwargs):
self = type.__new__(...) # this is PyType_FromSpec
# more stuff
```
So, I thought telling `PyType_FromSpec` that we are "inside" a custom `__new__`
is sufficient and that even as a flag passed as part of the spec could be
enough.
But... I agree that I do not quite see that it would be pretty, so it probably
was a bad idea :).
Plus, if you add a new method it should also solves the issue of setting the
`tp_type` slot to the metaclass explicitly when it is not implicit by
inheritance (which is the only thing I care about).
(PyType_FromSpec and PyType_ApplySpec will still need to do the work of
resolving the metaclass from the base classes, though.)
----------
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<https://bugs.python.org/issue45383>
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