Add a new check for the nonlocal variables without binding (close issue #582)fix-582

5 files changed, 51 insertions, 1 deletions

diff --git a/pylint/checkers/base.py b/pylint/checkers/base.py
index 6cff1e2..38cf0ab 100644
--- a/pylint/checkers/base.py
+++ b/pylint/checkers/base.py
@@ -328,6 +328,10 @@ class BasicErrorChecker(_BasicChecker):
                   'continue-in-finally',
                   'Emitted when the `continue` keyword is found '
                   'inside a finally clause, which is a SyntaxError.'),
+        'E0117': ("nonlocal variable without binding",
+                  'nonlocal-without-binding',
+                  'Emitted when a nonlocal variable is not bound',
+                  {'minversion': (3, 0)}),
         }
 
     @check_messages('function-redefined')
@@ -452,6 +456,29 @@ class BasicErrorChecker(_BasicChecker):
                 (node.operand.op == node.op)):
             self.add_message('nonexistent-operator', node=node, args=node.op*2)
 
+    def _check_nonlocal_without_binding(self, node, name):
+        current_scope = node.scope()
+        while True:
+            if current_scope.parent is None:
+                break
+
+            if not isinstance(current_scope, astroid.FunctionDef):
+                self.add_message('nonlocal-without-binding', node=node)
+                break
+            else:
+                if name not in current_scope.locals:
+                    current_scope = current_scope.parent.scope()
+                    continue
+                else:
+                    return
+
+        self.add_message('nonlocal-without-binding', node=node)
+
+    @check_messages('nonlocal-without-binding')
+    def visit_nonlocal(self, node):
+        for name in node.names:
+            self._check_nonlocal_without_binding(node, name)
+
     @check_messages('abstract-class-instantiated')
     def visit_call(self, node):
         """ Check instantiating abstract class with
diff --git a/pylint/test/functional/nonlocal_and_global.py b/pylint/test/functional/nonlocal_and_global.py
index c601a29..9400524 100644
--- a/pylint/test/functional/nonlocal_and_global.py
+++ b/pylint/test/functional/nonlocal_and_global.py
@@ -1,5 +1,5 @@
 """Test that a name is both nonlocal and global in the same scope."""

-# pylint: disable=missing-docstring,global-variable-not-assigned,invalid-name

+# pylint: disable=missing-docstring,global-variable-not-assigned,invalid-name,nonlocal-without-binding

 

 def bad(): # [nonlocal-and-global]

     nonlocal missing

diff --git a/pylint/test/functional/nonlocal_without_binding.py b/pylint/test/functional/nonlocal_without_binding.py
new file mode 100644
index 0000000..2871ed6
--- /dev/null
+++ b/pylint/test/functional/nonlocal_without_binding.py
@@ -0,0 +1,20 @@
+""" Checks that reversed() receive proper argument """
+# pylint: disable=missing-docstring
+# pylint: disable=too-few-public-methods,no-self-use,no-absolute-import,invalid-name,unused-variable
+
+def test():
+    def parent():
+        a = 42
+        def stuff():
+            nonlocal a
+
+    def parent2():
+        a = 42
+        def stuff():
+            def other_stuff():
+                nonlocal a
+
+b = 42
+def func():
+    def other_func():
+        nonlocal b  # [nonlocal-without-binding]
diff --git a/pylint/test/functional/nonlocal_without_binding.rc b/pylint/test/functional/nonlocal_without_binding.rc
new file mode 100644
index 0000000..a2ab06c
--- /dev/null
+++ b/pylint/test/functional/nonlocal_without_binding.rc
@@ -0,0 +1,2 @@
+[testoptions]
+min_pyver=3.0
\ No newline at end of file
diff --git a/pylint/test/functional/nonlocal_without_binding.txt b/pylint/test/functional/nonlocal_without_binding.txt
new file mode 100644
index 0000000..17a40ac
--- /dev/null
+++ b/pylint/test/functional/nonlocal_without_binding.txt
@@ -0,0 +1 @@
+nonlocal-without-binding:20:func.other_func:nonlocal variable without binding
\ No newline at end of file