In 0.3.7, attributes in the __dict__ of a class are now deleted by dill if they have the same name and value as an attribute of a superclass. For example:

import dill

class Foo:
    x = 1

class Bar(Foo):
    x = 1  # identical value as superclass

assert 'x' in Bar.__dict__  # passes

data = dill.dumps(Bar)
Bar2 = dill.loads(data)

assert 'x' in Bar2.__dict__  # fails with dill 0.3.7 (works with 0.3.6)

This behavior is caused by the _get_typedict_type function added in #577. Based on its docstring it seems the idea was to exclude inherited methods, but the code actually excludes any attribute whose value is identical to the inherited value. This is not safe (arguably even in the case of methods) because as the code above demonstrates, it changes the behavior of code which inspects the __dict__ directly. Obviously the above code is a toy example, but we have real code which does this (basically to set a non-inherited flag on classes) and which was broken by dill 0.3.7.

In case it matters, I'm using Python 3.11.1 on macOS; we've also seen the problem under Python 3.10.12 on Ubuntu.