Check that a class has an explicitly defined metaclass before emitting 'old-style-class' for Python 2.

This can catch metaclasses defined at module level, using `__metaclass__ = ...` syntax, which transforms all old style classes to newstyle.
Also, look for the .newstyle attribute instead of bases.

6 files changed, 30 insertions, 6 deletions

diff --git a/ChangeLog b/ChangeLog
index c6b9b03..dc85ee4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -68,6 +68,9 @@ ChangeLog for Pylint
 
     * Detect calls of the parent's __init__, through a binded super() call.
 
+    * Check that a class has an explicitly defined metaclass before
+      emitting 'old-style-class' for Python 2.
+
 
 2014-07-26  --  1.3.0
 
diff --git a/checkers/newstyle.py b/checkers/newstyle.py
index cc8f640..532f3f1 100644
--- a/checkers/newstyle.py
+++ b/checkers/newstyle.py
@@ -74,14 +74,14 @@ class NewStyleConflictChecker(BaseChecker):
 
     @check_messages('slots-on-old-class', 'old-style-class')
     def visit_class(self, node):
-        """check __slots__ usage
+        """ Check __slots__ in old style classes and old
+        style class definition.
         """
         if '__slots__' in node and not node.newstyle:
             self.add_message('slots-on-old-class', node=node)
-        # The node type could be class, exception, metaclass, or
-        # interface.  Presumably, the non-class-type nodes would always
-        # have an explicit base class anyway.
-        if not node.bases and node.type == 'class':
+        # If the class node is not marked as newstyle and it has no explicitly
+        # defined metaclass, then it's an old style class.
+        if not node.newstyle and node.type == 'class' and not node.metaclass():
             self.add_message('old-style-class', node=node)
 
     @check_messages('property-on-old-class')
diff --git a/test/functional/old_style_class_py27.py b/test/functional/old_style_class_py27.py
new file mode 100644
index 0000000..4073c73
--- /dev/null
+++ b/test/functional/old_style_class_py27.py
@@ -0,0 +1,17 @@
+""" Tests for old style classes. """

+# pylint: disable=no-init, too-few-public-methods, invalid-name

+

+class Old: # [old-style-class]

+    """ old style class """

+

+class Child(Old): # [old-style-class]

+    """ still an old style class """

+

+__metaclass__ = type

+

+class NotOldStyle:

+    """ Because I have a metaclass at global level. """

+

+class NotOldStyle2:

+    """ Because I have a metaclass at class level. """

+    __metaclass__ = type

diff --git a/test/functional/old_style_class_py27.rc b/test/functional/old_style_class_py27.rc
new file mode 100644
index 0000000..a650233
--- /dev/null
+++ b/test/functional/old_style_class_py27.rc
@@ -0,0 +1,2 @@
+[testoptions]
+max_pyver=3.0
diff --git a/test/functional/old_style_class_py27.txt b/test/functional/old_style_class_py27.txt
new file mode 100644
index 0000000..223233e
--- /dev/null
+++ b/test/functional/old_style_class_py27.txt
@@ -0,0 +1,2 @@
+old-style-class:4::Old-style class defined.
+old-style-class:7::Old-style class defined.
diff --git a/test/functional/undefined_variable.py b/test/functional/undefined_variable.py
index 25f0145..003708c 100644
--- a/test/functional/undefined_variable.py
+++ b/test/functional/undefined_variable.py
@@ -1,5 +1,5 @@
 """Test warnings about access to undefined variables."""
-# pylint: disable=too-few-public-methods, no-init, no-self-use
+# pylint: disable=too-few-public-methods, no-init, no-self-use, old-style-class
 
 DEFINED = 1