Add equality operator to policy.RuleDefault

There are occasions when comparing two RuleDefault objects is needed.
Rather than embedding the logic at the comparison site it's preferable
to let the object know how to compare itself to another.

Change-Id: I2eae5665fdecd6638e84f577b506314f7bc03fd3

oslo_policy/policy.py

@@ -706,3 +706,23 @@ class RuleDefault(object):
     def __str__(self):
         return '"%(name)s": "%(check_str)s"' % {'name': self.name,
                                                 'check_str': self.check_str}
+
+    def __eq__(self, other):
+        """Equality operator.
+
+        All check objects have a stable string representation. It is used for
+        comparison rather than check_str because multiple check_str's may parse
+        to the same check object. For instance '' and '@' are equivalent and
+        the parsed rule string representation for both is '@'.
+
+        The description does not play a role in the meaning of the check so it
+        is not considered for equality.
+        """
+        # Name should match, check should match, and class should be equivalent
+        # or one should be a subclass of the other.
+        if (self.name == other.name and
+                str(self.check) == str(other.check) and
+                (isinstance(self, other.__class__) or
+                 isinstance(other, self.__class__))):
+            return True
+        return False

oslo_policy/tests/test_policy.py

@@ -719,3 +719,57 @@ class RuleDefaultTestCase(base.PolicyBaseTestCase):
     def test_str(self):
         opt = policy.RuleDefault(name='foo', check_str='rule:foo')
         self.assertEqual('"foo": "rule:foo"', str(opt))
+
+    def test_equality_obvious(self):
+        opt1 = policy.RuleDefault(name='foo', check_str='rule:foo',
+                                  description='foo')
+        opt2 = policy.RuleDefault(name='foo', check_str='rule:foo',
+                                  description='bar')
+        self.assertEqual(opt1, opt2)
+
+    def test_equality_less_obvious(self):
+        opt1 = policy.RuleDefault(name='foo', check_str='',
+                                  description='foo')
+        opt2 = policy.RuleDefault(name='foo', check_str='@',
+                                  description='bar')
+        self.assertEqual(opt1, opt2)
+
+    def test_not_equal_check(self):
+        opt1 = policy.RuleDefault(name='foo', check_str='rule:foo',
+                                  description='foo')
+        opt2 = policy.RuleDefault(name='foo', check_str='rule:bar',
+                                  description='bar')
+        self.assertNotEqual(opt1, opt2)
+
+    def test_not_equal_name(self):
+        opt1 = policy.RuleDefault(name='foo', check_str='rule:foo',
+                                  description='foo')
+        opt2 = policy.RuleDefault(name='bar', check_str='rule:foo',
+                                  description='bar')
+        self.assertNotEqual(opt1, opt2)
+
+    def test_not_equal_class(self):
+        class NotRuleDefault(object):
+            def __init__(self, name, check_str):
+                self.name = name
+                self.check = _parser.parse_rule(check_str)
+
+        opt1 = policy.RuleDefault(name='foo', check_str='rule:foo')
+        opt2 = NotRuleDefault(name='foo', check_str='rule:foo')
+        self.assertNotEqual(opt1, opt2)
+
+    def test_equal_subclass(self):
+        class RuleDefaultSub(policy.RuleDefault):
+            pass
+
+        opt1 = policy.RuleDefault(name='foo', check_str='rule:foo')
+        opt2 = RuleDefaultSub(name='foo', check_str='rule:foo')
+        self.assertEqual(opt1, opt2)
+
+    def test_not_equal_subclass(self):
+        class RuleDefaultSub(policy.RuleDefault):
+            pass
+
+        opt1 = policy.RuleDefault(name='foo', check_str='rule:foo')
+        opt2 = RuleDefaultSub(name='bar', check_str='rule:foo')
+        self.assertNotEqual(opt1, opt2)