From af45b41f52ec1727c2a84777af0c2e55d6b8d912 Mon Sep 17 00:00:00 2001
From: Scott Sanderson <ssanderson@quantopian.com>
Date: Sun, 18 Feb 2018 18:21:26 -0500
Subject: Warn on raise NotImplemented(...)

This is a common mistake for `raise NotImplementedError`. Since
`NotImplemented` isn't an exception, it's never valid to raise
it (barring strange circumstances where you've aliased `NotImplemented`
in `__builtins__`).
---
 pyflakes/checker.py         | 26 +++++++++++++++++++++++++-
 pyflakes/messages.py        |  4 ++++
 pyflakes/test/test_other.py | 17 +++++++++++++++++
 3 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/pyflakes/checker.py b/pyflakes/checker.py
index 9b39e6c..0ee6189 100644
--- a/pyflakes/checker.py
+++ b/pyflakes/checker.py
@@ -38,10 +38,17 @@ if PY2:
     def getNodeType(node_class):
         # workaround str.upper() which is locale-dependent
         return str(unicode(node_class.__name__).upper())
+
+    def get_raise_argument(node):
+        return node.type
+
 else:
     def getNodeType(node_class):
         return node_class.__name__.upper()
 
+    def get_raise_argument(node):
+        return node.exc
+
     # Silence `pyflakes` from reporting `undefined name 'unicode'` in Python 3.
     unicode = str
 
@@ -138,6 +145,10 @@ def convert_to_value(item):
         return UnhandledKeyType()
 
 
+def is_notimplemented_name_node(node):
+    return isinstance(node, ast.Name) and getNodeName(node) == 'NotImplemented'
+
+
 class Binding(object):
     """
     Represents the binding of a value to a name.
@@ -965,7 +976,7 @@ class Checker(object):
 
     # "stmt" type nodes
     DELETE = PRINT = FOR = ASYNCFOR = WHILE = IF = WITH = WITHITEM = \
-        ASYNCWITH = ASYNCWITHITEM = RAISE = TRYFINALLY = EXEC = \
+        ASYNCWITH = ASYNCWITHITEM = TRYFINALLY = EXEC = \
         EXPR = ASSIGN = handleChildren
 
     PASS = ignore
@@ -989,6 +1000,19 @@ class Checker(object):
         EQ = NOTEQ = LT = LTE = GT = GTE = IS = ISNOT = IN = NOTIN = \
         MATMULT = ignore
 
+    def RAISE(self, node):
+        self.handleChildren(node)
+
+        arg = get_raise_argument(node)
+
+        if isinstance(arg, ast.Call):
+            if is_notimplemented_name_node(arg.func):
+                # Handle "raise NotImplemented(...)"
+                self.report(messages.RaiseNotImplemented, node)
+        elif is_notimplemented_name_node(arg):
+            # Handle "raise NotImplemented"
+            self.report(messages.RaiseNotImplemented, node)
+
     # additional node types
     COMPREHENSION = KEYWORD = FORMATTEDVALUE = JOINEDSTR = handleChildren
 
diff --git a/pyflakes/messages.py b/pyflakes/messages.py
index 670f95f..eb87a72 100644
--- a/pyflakes/messages.py
+++ b/pyflakes/messages.py
@@ -239,3 +239,7 @@ class ForwardAnnotationSyntaxError(Message):
     def __init__(self, filename, loc, annotation):
         Message.__init__(self, filename, loc)
         self.message_args = (annotation,)
+
+
+class RaiseNotImplemented(Message):
+    message = "'raise NotImplemented' should be 'raise NotImplementedError'"
diff --git a/pyflakes/test/test_other.py b/pyflakes/test/test_other.py
index 5bae7a0..c771ef6 100644
--- a/pyflakes/test/test_other.py
+++ b/pyflakes/test/test_other.py
@@ -1983,3 +1983,20 @@ class TestAsyncStatements(TestCase):
         self.flakes('''
         a: 'a: "A"'
         ''', m.ForwardAnnotationSyntaxError)
+
+    def test_raise_notimplemented(self):
+        self.flakes('''
+        raise NotImplementedError("This is fine")
+        ''')
+
+        self.flakes('''
+        raise NotImplementedError
+        ''')
+
+        self.flakes('''
+        raise NotImplemented("This isn't gonna work")
+        ''', m.RaiseNotImplemented)
+
+        self.flakes('''
+        raise NotImplemented
+        ''', m.RaiseNotImplemented)
-- 
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