bpo-39485: fix corner-case in method-detection of mock (GH-18255)

miss-islington · cfbolz · web-flow · commit 696d2324cf2a · 2020-01-29T16:15:36.000Z
Replace check for whether something is a method in the mock module. The previous version fails on PyPy, because there no method wrappers exist (everything looks like a regular Python-defined function). Thus the isinstance(getattr(result, '__get__', None), MethodWrapperTypes) check returns True for any descriptor, not just methods. This condition could also return erroneously True in CPython for C-defined descriptors. Instead to decide whether something is a method, just check directly whether it's a function defined on the class. This passes all tests on CPython and fixes the bug on PyPy. (cherry picked from commit a327677) Co-authored-by: Carl Friedrich Bolz-Tereick <cfbolz@gmx.de> Co-authored-by: Carl Friedrich Bolz-Tereick <cfbolz@gmx.de>
diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
@@ -2715,7 +2715,7 @@ def _must_skip(spec, entry, is_type):
             continue
         if isinstance(result, (staticmethod, classmethod)):
             return False
-        elif isinstance(getattr(result, '__get__', None), MethodWrapperTypes):
+        elif isinstance(result, FunctionTypes):
             # Normal method => skip if looked up on type
             # (if looked up on instance, self is already skipped)
             return is_type
@@ -2745,10 +2745,6 @@ def __init__(self, spec, spec_set=False, parent=None,
     type(ANY.__eq__),
 )
 
-MethodWrapperTypes = (
-    type(ANY.__eq__.__get__),
-)
-
 
 file_spec = None
 
diff --git a/Misc/NEWS.d/next/Library/2020-01-29-14-58-27.bpo-39485.Zy3ot6.rst b/Misc/NEWS.d/next/Library/2020-01-29-14-58-27.bpo-39485.Zy3ot6.rst
@@ -0,0 +1,3 @@
+Fix a bug in :func:`unittest.mock.create_autospec` that would complain about
+the wrong number of arguments for custom descriptors defined in an extension
+module returning functions.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	+Fix a bug in :func:`unittest.mock.create_autospec` that would complain about
	`2`	`+the wrong number of arguments for custom descriptors defined in an extension`
	`3`	`+module returning functions.`