This does not look like a bug to me.
What do you expect to happen?

Right now weakrefobject.c has these lines:

static PyObject *
weakref_repr(PyWeakReference *self)
{
    PyObject *name, *repr;
    PyObject* obj = PyWeakref_GET_OBJECT(self);

    if (obj == Py_None) {
        return PyUnicode_FromFormat("<weakref at %p; dead>", self);
    }

    Py_INCREF(obj);
    if (_PyObject_LookupAttr(obj, &_Py_ID(__name__), &name) < 0) {
        Py_DECREF(obj);
        return NULL;
    }
    // ...

It tries to get __name__ attribute from the passed object. Since __getattr__ tries to get __name__ from self - it fails with a KeyError. It works exactly as it is written.

To fix this you can do something like:

class MyConfig(dict):
    def __getattr__(self, x):
        if x in {'__name__', '__class__', 'whatever_else'}:
             return getattr(type(self), x)
        return self[x]

@sobolevn Thanks for your quick response! I do agree this works well in functionality's perspective, but I'd like to say if this is a good user experience. If users are just trying to override __getattr__ to implement their own functionality(like what I'm doing in the example), it means they should handle a lot of other python internal stuff at well. I think this would sort of increase the complexity, and make users can't focus on their own functionality.

So, probably you are asking from some kind of fallback for cases like this. Please, correct me if I am wrong :)

I think that repr() of weakref.ref would have a default value if _PyObject_LookupAttr(obj, &_Py_ID(__name__), &name) fails.

Example: <weakref at 0x1085b5800; to __some_default__ at 0x7ffd1071c080 (...)>

However, I don't think this is a good user experience either.
It is better to see an explicit exception early on than very strange and mostly unreadable repr somewhere in logs.

Considering your class, it looks problematic to me. It does not respect basic python's API, like: __dict__, __name__, __qualname__, __class__, __module__, etc.

They are quite basic, many other parts of CPython (and 3rd party projects) do use it.
And you will have a lot of other failure when these fundamentals cannot be accessed 🤔

Do you agree with me?