Fix B010 lambda flase positive (#246)

bugbear.py

@@ -326,7 +326,8 @@ def visit_Call(self, node):
                 ):
                     self.errors.append(B009(node.lineno, node.col_offset))
                 elif (
-                    node.func.id == "setattr"
+                    not any(isinstance(n, ast.Lambda) for n in self.node_stack)
+                    and node.func.id == "setattr"
                     and len(node.args) == 3
                     and _is_identifier(node.args[1])
                     and not iskeyword(node.args[1].s)

tests/b009_b010.py

@@ -1,6 +1,6 @@
 """
 Should emit:
-B009 - Line 17, 18, 19
+B009 - Line 17, 18, 19, 44
 B010 - Line 28, 29, 30
 """
 
@@ -28,3 +28,20 @@
 setattr(foo, "bar", None)
 setattr(foo, "_123abc", None)
 setattr(foo, "abc123", None)
+
+# Allow use of setattr within lambda expression
+# since assignment is not valid in this context.
+c = lambda x: setattr(x, "some_attr", 1)
+
+
+class FakeCookieStore:
+    def __init__(self, has_setter):
+        self.cookie_filter = None
+        if has_setter:
+            self.setCookieFilter = lambda func: setattr(self, "cookie_filter", func)
+
+
+# getattr is still flagged within lambda though
+c = lambda x: getattr(x, "some_attr")
+# should be replaced with
+c = lambda x: x.some_attr

tests/test_bugbear.py

@@ -169,6 +169,7 @@ def test_b009_b010(self):
             B010(28, 0),
             B010(29, 0),
             B010(30, 0),
+            B009(45, 14),
         ]
         self.assertEqual(errors, self.errors(*all_errors))