Class-based method stub cannot execute

[jonathan-benn]

class A:
	def B(self):
		return 5
stub = sinon.stub(A, 'B')
stub() # error

[note35]

In python3, this code works.

In python2, it will cause the error below.

Traceback (most recent call last):
  File "test.py", line 10, in <module>
    print(stub()) # error
  File "/Users/kir/python-dev/sinon/sinon/lib/base.py", line 135, in __call__
    return self._get_wrapper()(*args, **kwargs)
TypeError: unbound method wrapped() must be called with A instance as first argument (got nothing instead)

[jonathan-benn]

I suspect that this bug may have existed for a long time, since it's kind of the opposite of the issue that required the dirty hack in the first place.

The problem is that when trying to directly execute a class method (a class, not an object), Python is expecting the self argument as the first parameter to the function call.

Hence, the following code passes:

class A:
	def B(self):
		return 5
stub = sinon.stub(A, 'B')
stub(A()) # success!

This is because, as a language feature of Python, if you're calling the function B directly without an object then you must supply an instance. e.g.

o = A()
A.B(o) # returns 5

I'm not sure what you think the right thing to do would be in this case? One could consider the current behaviour of Sinon.PY to be correct. However, I do find it counter-intuitive (confusing) to need to pass an object instance into the stub.