Return empty lists for resources if neutron doesn't exist

It's the general design of the cloud layer to return empty resources
rather than throw exceptions when a user tries to fetch a non-existent
resource.

Change-Id: I1c6ce28af767f466f349b51a47abe27c0dcdd3fb

openstack/cloud/_network.py

@@ -123,6 +123,9 @@ class NetworkCloudMixin(_normalize.Normalizer):
         :returns: A list of ``munch.Munch`` containing network info.
 
         """
+        # If the cloud is running nova-network, just return an empty list.
+        if not self.has_service('network'):
+            return []
         # Translate None from search interface to empty {} for kwargs below
         if not filters:
             filters = {}
@@ -136,6 +139,9 @@ class NetworkCloudMixin(_normalize.Normalizer):
         :returns: A list of router ``munch.Munch``.
 
         """
+        # If the cloud is running nova-network, just return an empty list.
+        if not self.has_service('network'):
+            return []
         # Translate None from search interface to empty {} for kwargs below
         if not filters:
             filters = {}
@@ -152,6 +158,9 @@ class NetworkCloudMixin(_normalize.Normalizer):
         :returns: A list of subnet ``munch.Munch``.
 
         """
+        # If the cloud is running nova-network, just return an empty list.
+        if not self.has_service('network'):
+            return []
         # Translate None from search interface to empty {} for kwargs below
         if not filters:
             filters = {}
@@ -192,6 +201,9 @@ class NetworkCloudMixin(_normalize.Normalizer):
         return _utils._filter_list(self._ports, None, filters or {})
 
     def _list_ports(self, filters):
+        # If the cloud is running nova-network, just return an empty list.
+        if not self.has_service('network'):
+            return []
         resp = self.network.get("/ports.json", params=filters)
         data = proxy._json_response(
             resp,

openstack/tests/unit/cloud/test_shade.py

@@ -122,26 +122,10 @@ class TestShade(base.TestCase):
 
         self.assert_calls()
 
-    def test__neutron_exceptions_resource_not_found(self):
-        self.register_uris([
-            dict(method='GET',
-                 uri=self.get_mock_url(
-                     'network', 'public', append=['v2.0', 'networks.json']),
-                 status_code=404)
-        ])
-        self.assertRaises(exc.OpenStackCloudResourceNotFound,
-                          self.cloud.list_networks)
-        self.assert_calls()
-
-    def test__neutron_exceptions_url_not_found(self):
-        self.register_uris([
-            dict(method='GET',
-                 uri=self.get_mock_url(
-                     'network', 'public', append=['v2.0', 'networks.json']),
-                 status_code=404)
-        ])
-        self.assertRaises(exc.OpenStackCloudURINotFound,
-                          self.cloud.list_networks)
+    def test_neutron_not_found(self):
+        self.use_nothing()
+        self.cloud.has_service = mock.Mock(return_value=False)
+        self.assertEqual([], self.cloud.list_networks())
         self.assert_calls()
 
     def test_list_servers(self):

releasenotes/notes/list-network-resources-empty-list-6aa760c01e7d97d7.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Basic networking list calls in the cloud layer been fixed to return
+    an empty list if neutron is not running.