Coerce role-principal values to frozenset.

Author: Luke Sneeringer

packages/google-cloud-core/google/cloud/iam.py

@@ -71,7 +71,7 @@ def __getitem__(self, key):
         return self._bindings[key]
 
     def __setitem__(self, key, value):
-        self._bindings[key] = value
+        self._bindings[key] = frozenset(value)
 
     def __delitem__(self, key):
         del self._bindings[key]

packages/google-cloud-core/tests/unit/test_iam.py

@@ -58,11 +58,12 @@ def test___getitem___miss(self):
 
     def test___setitem__(self):
         USER = 'user:phred@example.com'
+        PRINCIPALS = frozenset([USER])
         policy = self._make_one()
         policy['rolename'] = [USER]
-        self.assertEqual(policy['rolename'], [USER])
+        self.assertEqual(policy['rolename'], PRINCIPALS)
         self.assertEqual(len(policy), 1)
-        self.assertEqual(dict(policy), {'rolename': [USER]})
+        self.assertEqual(dict(policy), {'rolename': PRINCIPALS})
 
     def test___delitem___hit(self):
         policy = self._make_one()