Fix unused-import false positive with Python 3 metaclasses. Closes issue #143.

4 files changed, 45 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index da62285..9b675d0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,9 @@
 ChangeLog for Pylint
 ====================
 
+--
+    * Fix unused-import false positive with Python 3 metaclasses (#143).
+
 2014-04-30  --  1.2.1
     * Restore the ability to specify the init-hook option via the
       configuration file, which was accidentally broken in 1.2.0.
diff --git a/checkers/variables.py b/checkers/variables.py
index a6123de..dc8d111 100644
--- a/checkers/variables.py
+++ b/checkers/variables.py
@@ -716,6 +716,22 @@ class VariablesChecker3k(VariablesChecker):
         # do not check for not used locals here
         self._to_consume.pop()
 
+    def leave_module(self, node):
+        """ Update consumption analysis variable
+        for metaclasses.
+        """
+        for klass in node.nodes_of_class(astroid.Class):
+            if klass._metaclass:
+                metaclass = klass.metaclass()
+                module_locals = self._to_consume[0][0]
+
+                if isinstance(klass._metaclass, astroid.Name):
+                    module_locals.pop(klass._metaclass.name, None)
+                if metaclass:                
+                    # if it uses a `metaclass=module.Class`                            
+                    module_locals.pop(metaclass.root().name, None)
+        super(VariablesChecker3k, self).leave_module(node)
+
 if sys.version_info >= (3, 0):
     VariablesChecker = VariablesChecker3k
 
diff --git a/test/input/func_unused_import_py30.py b/test/input/func_unused_import_py30.py
new file mode 100644
index 0000000..ae6db93
--- /dev/null
+++ b/test/input/func_unused_import_py30.py
@@ -0,0 +1,20 @@
+"""check unused import for metaclasses
+"""
+__revision__ = 1
+import abc
+import sys
+from abc import ABCMeta
+from abc import ABCMeta as SomethingElse
+
+class Meta(metaclass=abc.ABCMeta):
+    """ Test """
+    def __init__(self):
+        self.data = sys.executable
+        self.test = abc
+
+class Meta2(metaclass=ABCMeta):
+    """ Test """
+
+class Meta3(metaclass=SomethingElse):
+    """ test """
+
diff --git a/test/messages/func_unused_import_py30.txt b/test/messages/func_unused_import_py30.txt
new file mode 100644
index 0000000..72a21fe
--- /dev/null
+++ b/test/messages/func_unused_import_py30.txt
@@ -0,0 +1,6 @@
+R:  9:Meta: Too few public methods (0/2)

+R: 15:Meta2: Too few public methods (0/2)

+R: 18:Meta3: Too few public methods (0/2)

+W:  7: Reimport 'ABCMeta' (imported line 6)

+W: 15:Meta2: Class has no __init__ method

+W: 18:Meta3: Class has no __init__ method
\ No newline at end of file