I may be completely misunderstanding here, but: here's a reproducible example:

class MyMeta(type):
    def __new__(cls, *args, **kwargs):
        print('__new__', *args, **kwargs)
        super().__new__(cls, *args, **kwargs)
    
    def __init__(self, a):
        print('__init__', *args, **kwargs)
        super().__init__(*args, **kwargs)

class A(metaclass=MyMeta):
    pass

MyMeta('A', (), {'__module__': '__main__', '__qualname__': 'A'})


Output:

__new__ A () {'__module__': '__main__', '__qualname__': 'A'}
__new__ A () {'__module__': '__main__', '__qualname__': 'A'}

Is this by design?

Your metaclass.__new__ method returns None instead of the new class. The rule for calling __init__ is:

- if the constructor __new__ returns an instance of the type, then call the initializer __init__

- otherwise, don't call __init__ at all.

https://docs.python.org/3/reference/datamodel.html#object.__new__

Since your __new__ accidentally returns None, the __init__ is not called. If you change the line to say 

return super().__new__(cls, *args, **kwargs)

you will see that __init__ is called. (And discover the bugs in your init method :-)

Ah, I wasn't aware I had to return...

The bug was deliberate to show that not even a different signature makes a difference. ;)

nosy: + steven.daprano
messages: + msg337085

resolution: not a bug
stage: resolved