False Negative - Python abc.ABC makes method's getACall unavailable

[fubuki8087]

If we have this Python code:

class MyClass():
    def method(self):
        print("xxx")
    def wrapper(self):
        self.method()

mc = MyClass()
mc.method()

and this query:

import python

from PythonFunctionValue method
select method.getACall()

It's OK that self.method() and mc.method() will be marked as positive.

However, those will be false negative as long as the class MyClass inherits abc.ABC. It looks like:

from abc import ABC

class MyClass(ABC):
    def method(self):
        print("xxx")
    def wrapper(self):
        self.method()

mc = MyClass()
mc.method()

Why does the abc.ABC make the result wrong?

[jketema]

Hi @fubuki8087

I've asked the CodeQL Python team to take a look.

[yoff]

Hi @fubuki8087, the PythonFunctionValue API is not really maintained anymore (it uses an old implementation of the call graph which was discarded precisely because of instabilities like the one you see). Unfortunately, we have not gotten around to expose the new call graph nicely. Partly because direct access to call resolution is rarely needed. But in case you do really need it, this comment shows you how to dig out the new call resolution predicate.

[fubuki8087]

@yoff Now I understand why wrapper and method were not resolved to function values. This is because the ABC class they inherit from is constructed using a metaclass.

Actually, I just simply want to find all the call sites of a specific method (e.g. MyClass.methodName). However, this method might not be resolved due to the class it belongs to inheriting (directly or indirectly) from the ABC class (or any other unresolvable class), ultimately causing the call sites to be unfindable.

The comment you provided does indeed solve this issue.