Merge pull request #44 from edx/ned/fix-43

Stop false warnings on chained comparisons. Fixes #43

edx_lint/pylint/right_assert_check.py

@@ -18,8 +18,8 @@ def register_checkers(linter):
 
 class AssertChecker(BaseChecker):
     """
-    Implements a few pylint checks on unitests asserts - making sure the right assert is used if assertTrue or
-    assertFalse are misused.
+    Implements a few pylint checks on unitests asserts - making sure the right
+    assert is used if assertTrue or assertFalse are misused.
     """
 
     __implements__ = (IAstroidChecker,)
@@ -77,7 +77,8 @@ class AssertChecker(BaseChecker):
         Check that various assertTrue/False functions are not misused.
         """
         if not isinstance(node.func, astroid.Getattr):
-            # If it isn't a getattr ignore this. All the assertMethods are attrs of self:
+            # If it isn't a getattr ignore this. All the assertMethods are
+            # attributes of self:
             return
 
         if node.func.attrname not in self.AFFECTED_ASSERTS:
@@ -88,6 +89,10 @@ class AssertChecker(BaseChecker):
         existing_code = "%s(%s)" % (node.func.attrname, first_arg.as_string())
 
         if isinstance(first_arg, astroid.Compare):
+            if len(first_arg.ops) > 1:
+                # This is a chained comparison, which we can't do anything with.
+                return
+
             compare = first_arg.ops[0][0]
             right = first_arg.ops[0][1]
             if isinstance(right, astroid.Const) and right.value is None:

test/input/func_asserts_check.py

@@ -56,3 +56,13 @@ class TestStringMethods(unittest.TestCase):
         This uses the wrong assert, but has a pragma to quiet the message.
         """
         self.assertTrue("a" in "lala")      # pylint: disable=wrong-assert-type
+
+    def test_chained_comparisons(self):
+        """
+        These uses of assertTrue and assertFalse are fine, because we can't
+        pick apart the chained comparisons.
+        """
+        my_value = my_other_value = 10
+        self.assertTrue(0 < my_value < 1000)
+        self.assertFalse(0 < my_value < 5)
+        self.assertTrue(my_value == my_other_value == 10)