__setattr__ not called on Metaclass

[slozier]

Discussed in #1660

^{Originally posted by zwadar February 23, 2023}
Hi,
I'm using 3.4.0 and trying to use setattr on a metaclass but it doesn't seem to be called. As far as I can see this should be supported and I don't see any issues reported, so I was wondering if I might be doing something wrong?

class Test(type):
    def __new__(cls, name, bases, namespace):
        cls = super(Test, cls).__new__(cls, name, bases, namespace)
        return cls        

    def __setattr__(cls, attr, value):
        print("Called Set Attr")
        super(Test, self).__setattr__(attr, value)

class TestMeta(object, metaclass=Test):
    aaa = 10

TestMeta.aaa = 80
print(TestMeta.aaa)

but the printed output is just

80

Can I somehow overcome it? This is pretty crucial to me.

Thank you

---

Here's a potential test case:

class Test(type):
    def __setattr__(cls, attr, value):
        super().__setattr__("last_attr", (attr, value))
        super().__setattr__(attr, value)

class TestMeta(metaclass=Test):
    aaa = 10

TestMeta.aaa = 80

assert TestMeta.aaa == 80
assert TestMeta.last_attr == ("aaa", 80)

[zwadar]

fiy I had tried to fix it by changing the line
https://github.com/IronLanguages/ironpython3/blob/master/Src/IronPython/Runtime/Types/PythonType.cs#L1304

to
((BuiltinMethodDescriptor)pts).DeclaringType == typeof(PythonType);

and it actually worked, except it had broke ctypes tests. But I supposes this method is the one that needs fixing.