Enhance used-before-assignment check to look for nonlocal uses.

4 files changed, 58 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index f5b7192..c3c05e7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,10 @@
 ChangeLog for Pylint
 ====================
 
+--
+    * Enhance the check for 'used-before-assignment' to look
+      for 'nonlocal' uses.
+
 2013-12-22  --  1.1.0
     * Add new check for use of deprecated pragma directives "pylint:disable-msg"
       or "pylint:enable-msg" (I0022, deprecated-pragma) which was previously
diff --git a/checkers/variables.py b/checkers/variables.py
index 90b7fe7..4ad82c4 100644
--- a/checkers/variables.py
+++ b/checkers/variables.py
@@ -507,6 +507,31 @@ builtins. Remember that you should avoid to define new builtins when possible.'
                     # defined in global or builtin scope
                     if defframe.root().lookup(name)[1]:
                         maybee0601 = False
+                    else:
+                         # check if we have a nonlocal
+                         frame = node.frame()
+                         frame_parent = frame.parent
+                         if (isinstance(frame, astroid.Function) and
+                             isinstance(frame_parent, astroid.Function)):
+                             # detect that the name exists
+                             # in the upper level
+                             defined_higher = False
+                             for assign in frame_parent.get_children():
+                                 if not isinstance(assign, astroid.Assign):
+                                     continue
+                                 for target in assign.targets:
+                                     if (isinstance(target, astroid.AssName) and
+                                         target.name == name):
+                                         defined_higher = True
+                                         break
+                                 if defined_higher:
+                                     break                                     
+                             for child in frame.get_children():
+                                 if not isinstance(child, astroid.Nonlocal):
+                                     continue
+                                 if name in child.names and defined_higher:
+                                     maybee0601 = False
+                                     break
                 if (maybee0601
                     and stmt.fromlineno <= defstmt.fromlineno
                     and not is_defined_before(node)
diff --git a/test/input/func_used_before_assignment_py30.py b/test/input/func_used_before_assignment_py30.py
new file mode 100644
index 0000000..04987f3
--- /dev/null
+++ b/test/input/func_used_before_assignment_py30.py
@@ -0,0 +1,27 @@
+"""Check for nonlocal and used-before-assignment"""

+# pylint: disable=missing-docstring, unused-variable

+

+__revision__ = 0

+

+def test_ok():

+    """ uses nonlocal """

+    cnt = 1

+    def wrap():

+        nonlocal cnt

+        cnt = cnt + 1

+    wrap()

+

+def test_fail():

+    """ doesn't use nonlocal """

+    cnt = 1

+    def wrap():

+        cnt = cnt + 1

+    wrap()

+

+def test2_fail():

+    """ uses nonlocal, but without an

+    outer label defined. """

+    def wrap():

+        nonlocal cnt

+        cnt = cnt + 1

+    wrap()

diff --git a/test/messages/func_used_before_assignment_py30.txt b/test/messages/func_used_before_assignment_py30.txt
new file mode 100644
index 0000000..f731b3c
--- /dev/null
+++ b/test/messages/func_used_before_assignment_py30.txt
@@ -0,0 +1,2 @@
+E: 18:test_fail.wrap: Using variable 'cnt' before assignment

+E: 26:test2_fail.wrap: Using variable 'cnt' before assignment
\ No newline at end of file