handle del inside function definition

pyflakes/checker.py

@@ -16,6 +16,11 @@
 import sys
 import tokenize
 
+try:
+    from collections import UserDict
+except ImportError:
+    from UserDict import IterableUserDict as UserDict
+
 from pyflakes import messages
 
 PY2 = sys.version_info < (3, 0)
@@ -537,9 +542,13 @@ def _add_to_names(container):
         super(ExportBinding, self).__init__(name, source)
 
 
-class Scope(dict):
+class Scope(UserDict, object):
     importStarred = False       # set to True when import * is found
 
+    def __init__(self, *args, **kwargs):
+        super(Scope, self).__init__(*args, **kwargs)
+        self.deleted_names = []
+
     def __repr__(self):
         scope_cls = self.__class__.__name__
         return '<%s at 0x%x %s>' % (scope_cls, id(self), dict.__repr__(self))
@@ -559,8 +568,8 @@ class FunctionScope(Scope):
     alwaysUsed = {'__tracebackhide__', '__traceback_info__',
                   '__traceback_supplement__'}
 
-    def __init__(self):
-        super(FunctionScope, self).__init__()
+    def __init__(self, *args, **kwargs):
+        super(FunctionScope, self).__init__(*args, **kwargs)
         # Simplify: manage the special locals as globals
         self.globals = self.alwaysUsed.copy()
         self.returnValue = None     # First non-empty return
@@ -1023,6 +1032,10 @@ def handleNodeLoad(self, node):
         in_generators = None
         importStarred = None
 
+        if name in self.scope.deleted_names:
+            self.report(messages.UndefinedName, node, name)
+            return
+
         # try enclosing function scopes and global scope
         for scope in self.scopeStack[-1::-1]:
             if isinstance(scope, ClassScope):
@@ -1093,6 +1106,8 @@ def handleNodeStore(self, node):
         name = getNodeName(node)
         if not name:
             return
+        if name in self.scope.deleted_names:
+            self.scope.deleted_names.remove(name)
         # if the name hasn't already been defined in the current scope
         if isinstance(self.scope, FunctionScope) and name not in self.scope:
             # for each function or module scope above us
@@ -1146,11 +1161,14 @@ def on_conditional_branch():
 
         if isinstance(self.scope, FunctionScope) and name in self.scope.globals:
             self.scope.globals.remove(name)
+            self.scope.deleted_names.append(name)
         else:
             try:
                 del self.scope[name]
             except KeyError:
                 self.report(messages.UndefinedName, node, name)
+            else:
+                self.scope.deleted_names.append(name)
 
     def _handle_type_comments(self, node):
         for (lineno, col_offset), comment in self._type_comments.get(node, ()):

pyflakes/test/test_undefined_names.py

@@ -446,6 +446,43 @@ def _worker():
                 o = False
         ''')
 
+    def test_delFunctionScope(self):
+        """
+        Global names should not be seen if there are same names
+        defined in function.
+        """
+        self.flakes('''
+        a = 1
+        def func():
+            a = 2
+            del a
+            a
+        ''', m.UndefinedName)
+
+    def test_delMethodScope(self):
+        """
+        Global names should not be seen if there are same names
+        defined in method.
+        """
+        self.flakes('''
+        a = 1
+        class A(object):
+            def method(self):
+                a = 2
+                del a
+                a
+        ''', m.UndefinedName)
+
+    def test_RedefinedDeletedName(self):
+        self.flakes('''
+        a = 1
+        def func():
+            a = 2
+            del a
+            a = 3
+            a
+        ''')
+
     def test_globalFromNestedScope(self):
         """Global names are available from nested scopes."""
         self.flakes('''