Add support for unbalanced tuple unpacking check.

3 files changed, 35 insertions, 0 deletions

diff --git a/checkers/variables.py b/checkers/variables.py
index 07156d1..e59a304 100644
--- a/checkers/variables.py
+++ b/checkers/variables.py
@@ -118,6 +118,12 @@ MSGS = {
               'Used when an loop variable (i.e. defined by a for loop or \
               a list comprehension or a generator expression) is used outside \
               the loop.'),
+
+    'W0632': ('Possible unbalanced tuple unpacking: '
+              'left side has %d label(s), right side has %d value(s)',
+              'unbalanced-tuple-unpacking',
+              'Used when there is an unbalanced tuple unpacking in assignment'),
+
     }
 
 class VariablesChecker(BaseChecker):
@@ -536,6 +542,26 @@ builtins. Remember that you should avoid to define new builtins when possible.'
                 continue
             self._check_module_attrs(node, module, name.split('.'))
 
+    @check_messages('W0632')
+    def visit_assign(self, node):
+         """ Check unbalanced tuple unpacking for assignments. """
+         if not isinstance(node.value, astroid.Tuple):
+             return
+         if not isinstance(node.targets[0], astroid.Tuple):
+             return
+
+         targets = node.targets[0].itered()
+         values = node.value.itered()
+
+         if any(not isinstance(target_node, astroid.AssName)
+                for target_node in targets):
+             return
+
+         if len(targets) != len(values):
+             self.add_message('W0632',
+                              node=node,
+                              args=(len(targets), len(values)))
+
     def _check_module_attrs(self, node, module, module_names):
         """check that module_names (list of string) are accessible through the
         given module
diff --git a/test/input/func_w0632.py b/test/input/func_w0632.py
new file mode 100644
index 0000000..6437a50
--- /dev/null
+++ b/test/input/func_w0632.py
@@ -0,0 +1,8 @@
+"""Check possible unbalanced tuple unpacking """
+
+__revision__ = 0
+
+def do_stuff():
+    """This is not right."""
+    first, second = 1, 2, 3
+    return first + second
diff --git a/test/messages/func_w0632.txt b/test/messages/func_w0632.txt
new file mode 100644
index 0000000..c4c2d03
--- /dev/null
+++ b/test/messages/func_w0632.txt
@@ -0,0 +1 @@
+W:  7:do_stuff: Possible unbalanced tuple unpacking: left side has 2 label(s), right side has 3 value(s)
\ No newline at end of file