Merge "Remove extra GET call when limit provided to list"

openstack/resource.py

@@ -469,11 +469,19 @@ class Resource(collections.MutableMapping):
             if not resp:
                 more_data = False
 
+            # Keep track of how many items we've yielded. If we yielded
+            # less than our limit, we don't need to do an extra request
+            # to get back an empty data set, which acts as a sentinel.
+            yielded = 0
             for data in resp:
                 value = cls.existing(**data)
                 marker = value.id
+                yielded += 1
                 yield value
 
+            if limit and yielded < limit:
+                more_data = False
+
     @classmethod
     def find(cls, session, name_or_id, path_args=None):
         """Find a resource by name or id as an instance."""

openstack/tests/test_resource.py

@@ -324,6 +324,18 @@ class ResourceTests(base.TestTransportBase):
             self.assertEqual(fake_name, obj.name)
             self.assertIsInstance(obj, FakeResource)
 
+    def test_list_bail_out(self):
+        results = [fake_data.copy(), fake_data.copy(), fake_data.copy()]
+        body = mock.Mock(body={fake_resources: results})
+        attrs = {"get.return_value": body}
+        session = mock.Mock(**attrs)
+
+        list(FakeResource.list(session, limit=len(results) + 1,
+                               path_args=fake_arguments))
+
+        # Ensure we only made one call to complete this.
+        self.assertEqual(session.get.call_count, 1)
+
     def test_attrs(self):
         obj = FakeResource()