Use assertIsNone instead of assertEqual(None, *)

One should replace assertEqual(None, *) with assertIsNone in tests
that validate that a variable is None.

This is based on commit 33a459c2c309670b0fcb2fcac5d128e802be7a69

Change-Id: I7794934f5c2267125bafb9d9953352daa68c39a7

HACKING.rst

@@ -21,3 +21,4 @@ Neutron Library Specific Commandments
 - [N533] Validate that debug level logs are not translated
 - [N534] Exception messages should be translated
 - [N535] Usage of Python eventlet module not allowed
+- [N536] Use assertIsNone/assertIsNotNone rather than assertEqual/assertIs to check None values.

neutron_lib/hacking/checks.py

@@ -37,6 +37,11 @@ namespace_imports_from_dot = re.compile(r"from[\s]+([\w]+)[.]")
 namespace_imports_from_root = re.compile(r"from[\s]+([\w]+)[\s]+import[\s]+")
 contextlib_nested = re.compile(r"^\s*with (contextlib\.)?nested\(")
 
+assert_equal_none_re = re.compile(
+    r"assertEqual\(.*?,\s+None\)|assertEqual\(None,")
+assert_is_none_re = re.compile(
+    r"assertIs(Not)?\(.*,\s+None\)|assertIs(Not)?\(None,")
+
 
 def use_jsonutils(logical_line, filename):
     """N521 - jsonutils must be used instead of json.
@@ -223,6 +228,19 @@ def check_no_eventlet_imports(logical_line):
         yield logical_line.index('eventlet'), msg
 
 
+def assert_equal_none(logical_line):
+    """N536 - Use assertIsNone."""
+    if assert_equal_none_re.search(logical_line):
+        msg = ("N536: Use assertIsNone rather than assertEqual "
+               "to check for None values")
+        yield logical_line.index('assert'), msg
+
+    if assert_is_none_re.search(logical_line):
+        msg = ("N536: Use assertIsNone or assertIsNotNone rather than "
+               "assertIs or assertIsNone to check for None values.")
+        yield logical_line.index('assert'), msg
+
+
 def factory(register):
     """Hacking check factory for neutron-lib adopter compliant checks.
 
@@ -255,6 +273,7 @@ def incubating_factory(register):
     :param register: The function to register the check functions with.
     :returns: None.
     """
+    register(assert_equal_none)
 
 
 def _neutron_lib_factory(register):

neutron_lib/tests/unit/hacking/test_checks.py

@@ -225,3 +225,25 @@ class HackingTestCase(base.BaseTestCase):
         self.assertLinePasses(f, 'print("eventlet not here")')
         self.assertLinePasses(f, 'print("eventlet.timeout")')
         self.assertLinePasses(f, "from mymod.timeout import (eventlet, X)")
+
+    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(A, None)  # Comment"))), 1)
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "self.assertEqual(None, A)"))), 1)
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "self.assertEqual(None, A)  # Comment"))), 1)
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "assertIsNot(A, None)"))), 1)
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "assertIsNot(A, None)  # Comment"))), 1)
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "assertIsNot(None, A)"))), 1)
+        self.assertEqual(len(list(checks.assert_equal_none(
+            "assertIsNot(None, A)  # Comment"))), 1)
+        self.assertEqual(
+            len(list(checks.assert_equal_none("self.assertIsNone(A)"))), 0)
+        self.assertEqual(
+            len(list(checks.assert_equal_none("self.assertIsNotNone(A)"))), 0)

releasenotes/notes/hacking-check-n537-280ec39c061d9dd7.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - Added hacking check ``N536``. This hacking check is added to the
+    incubating checks.