Enforce style check for assertIsNone

The following checks is added in this commit:
* enforce assertIsNone instead of assertEqual with a None

Change-Id: Idc7c5cb53060dad544bb9b8659e7220b7cd41e56
Partial-Implements: blueprint mistral-hacking

HACKING.rst

@@ -0,0 +1,10 @@
+Style Commandments
+==================
+
+Read the OpenStack Style Commandments http://docs.openstack.org/developer/hacking/
+
+Mistral Specific Commandments
+-----------------------------
+
+- [M318] Change assertEqual(A, None) or assertEqual(None, A) by optimal assert
+  like assertIsNone(A)

mistral/hacking/checks.py

@@ -30,6 +30,23 @@ import six
 oslo_namespace_imports_dot = re.compile(r"import[\s]+oslo[.][^\s]+")
 oslo_namespace_imports_from_dot = re.compile(r"from[\s]+oslo[.]")
 oslo_namespace_imports_from_root = re.compile(r"from[\s]+oslo[\s]+import[\s]+")
+assert_equal_end_with_none_re = re.compile(
+    r"(.)*assertEqual\((\w|\.|\'|\"|\[|\])+, None\)")
+assert_equal_start_with_none_re = re.compile(
+    r"(.)*assertEqual\(None, (\w|\.|\'|\"|\[|\])+\)")
+
+
+def assert_equal_none(logical_line):
+    """Check for assertEqual(A, None) or assertEqual(None, A) sentences
+
+    M318
+    """
+    msg = ("M318: assertEqual(A, None) or assertEqual(None, A) "
+           "sentences not allowed. Use assertIsNone instead.")
+    res = (assert_equal_start_with_none_re.match(logical_line) or
+           assert_equal_end_with_none_re.match(logical_line))
+    if res:
+        yield (0, msg)
 
 
 def check_oslo_namespace_imports(logical_line):
@@ -210,5 +227,6 @@ class CheckForLoggingIssues(BaseASTChecker):
 
 
 def factory(register):
+    register(assert_equal_none)
     register(check_oslo_namespace_imports)
     register(CheckForLoggingIssues)

mistral/tests/unit/hacking/test_checks.py

@@ -59,6 +59,16 @@ class BaseLoggingCheckTest(base.BaseTest):
 
         self.assertEqual(expected_errors or [], actual_errors)
 
+    def test_assert_equal_none(self):
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "self.assertEqual(A, None)"))), 1)
+
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "self.assertEqual(None, A)"))), 1)
+
+        self.assertEqual(
+            len(list(checks.assert_equal_none("self.assertIsNone()"))), 0)
+
 
 class TestLoggingWithWarn(BaseLoggingCheckTest):