Merge pyflakes-class-decorator-2863

Author: exarkun
Reviewer: mithrandi
Fixes: #2863

Add support for recognizing names used with the class decorator syntax, both so
that a name used in such a way is recognized as used (ie, not unused) and so that
undefined names used in such a way are reported as such.

Author: exarkun

pyflakes/checker.py

@@ -328,14 +328,23 @@ def addArgs(arglist):
 
         self.defer(runFunction)
 
+
     def CLASS(self, node):
+        """
+        Check names used in a class definition, including its decorators, base
+        classes, and the body of its definition.  Additionally, add its name to
+        the current scope.
+        """
+        if getattr(node, "decorators", None) is not None:
+            self.handleChildren(node.decorators)
         self.addBinding(node.lineno, Assignment(node.name, node))
         for baseNode in node.bases:
             self.handleNode(baseNode)
         self.pushClassScope()
         self.handleChildren(node.code)
         self.popScope()
 
+
     def ASSNAME(self, node):
         if node.flags == 'OP_DELETE':
             if isinstance(self.scope, FunctionScope) and node.name in self.scope.globals:

pyflakes/test/test_imports.py

@@ -510,3 +510,38 @@ def f():
         def f():
             return "hello"
         ''', m.UndefinedName)
+
+
+class Python26Tests(harness.Test):
+    """
+    Tests for checking of syntax which is valid in PYthon 2.6 and newer.
+    """
+    if version_info < (2, 6):
+        skip = "Python 2.6 required for class decorator tests."
+
+
+    def test_usedAsClassDecorator(self):
+        """
+        Using an imported name as a class decorator results in no warnings,
+        but using an undefined name as a class decorator results in an
+        undefined name warning.
+        """
+        self.flakes('''
+        from interior import decorate
+        @decorate
+        class foo:
+            pass
+        ''')
+
+        self.flakes('''
+        from interior import decorate
+        @decorate("foo")
+        class bar:
+            pass
+        ''')
+
+        self.flakes('''
+        @decorate
+        class foo:
+            pass
+        ''', m.UndefinedName)