Suppress false-positive not-callable messages from class descriptors (#1911)

This is a holdover until astroid can be fixed. Astroid needs to understand descriptors or at least raise Uninferable instead of allowing the descriptor instance through Close #1699

Author: brycepg

ChangeLog

@@ -97,6 +97,11 @@ What's New in Pylint 2.0?
 
  Close #1599
 
+ * Suppress false-positive ``not-callable`` messages from certain
+ staticmethod descriptors
+
+ Close #1699
+
 What's New in Pylint 1.8.1?
 =========================
 

doc/whatsnew/2.0.rst

@@ -45,3 +45,6 @@ Other Changes
 
 * Fix false positive ``undefined-variable`` for lambda argument in
  class definitions
+
+* Suppress false-positive ``not-callable`` messages from certain
+ staticmethod descriptors

pylint/checkers/typecheck.py

@@ -875,8 +875,13 @@ def visit_call(self, node):
 
  called = safe_infer(node.func)
  # only function, generator and object defining __call__ are allowed
+ # Ignore instances of descriptors since astroid cannot properly handle them
+ # yet
  if called and not called.callable():
- if isinstance(called, astroid.Instance) and not has_known_bases(called):
+ if isinstance(called, astroid.Instance) and (
+ not has_known_bases(called)
+ or (isinstance(called.scope(), astroid.ClassDef)
+ and '__get__' in called.locals)):
  # Don't emit if we can't make sure this object is callable.
  pass
  else:

pylint/test/unittest_checker_typecheck.py

@@ -229,3 +229,36 @@ def test_typing_namedtuple_unsubscriptable_object_issue1295(self):
  subscript = module.body[-1].value
  with self.assertNoMessages():
  self.checker.visit_subscript(subscript)
+
+ def test_staticmethod_multiprocessing_call(self):
+ """Make sure not-callable isn't raised for descriptors
+
+ astroid can't process descriptors correctly so
+ pylint needs to ignore not-callable for them
+ right now
+
+ Test for https://github.com/PyCQA/pylint/issues/1699
+ """
+ call = astroid.extract_node("""
+ import multiprocessing
+ multiprocessing.current_process() #@
+ """)
+ with self.assertNoMessages():
+ self.checker.visit_call(call)
+
+ def test_descriptor_call(self):
+ call = astroid.extract_node("""
+ def func():
+ pass
+
+ class ADescriptor:
+ def __get__(self, instance, owner):
+ return func
+
+ class AggregateCls:
+ a = ADescriptor()
+
+ AggregateCls().a() #@
+ """)
+ with self.assertNoMessages():
+ self.checker.visit_call(call)