Make get_stack fetch a single full stack

There is a convention in shade for get_<entity> calls to do a
list_<entities> with no server filtering then do a client-side filter
to return a single result. This approach is not appropriate for Heat
since the stacks.list call returns significantly less detail than the
stacks.get call.

A user calling get_stack will almost certainly be wanting the extra
detail provided by the proper stacks.get (for example, the stack
outputs).

This change switches to using stacks.get for the get_stack
implementation. It replaces the search_stacks call with a local
function that returns a 'list' of one full stack object.

Change-Id: I5d326d489f806709252a22360f3dbd8011fdb9c7

shade/_tasks.py

@@ -735,3 +735,8 @@ class StackCreate(task_manager.Task):
 class StackDelete(task_manager.Task):
     def main(self, client):
         return client.heat_client.stacks.delete(self.args['id'])
+
+
+class StackGet(task_manager.Task):
+    def main(self, client):
+        return client.heat_client.stacks.get(**self.args)

shade/openstackcloud.py

@@ -1669,8 +1669,18 @@ class OpenStackCloud(object):
         :raises: ``OpenStackCloudException`` if something goes wrong during the
             openstack API call or if multiple matches are found.
         """
+
+        def search_one_stack(name_or_id=None, filters=None):
+            # stack names are mandatory and enforced unique in the project
+            # so a StackGet can always be used for name or ID.
+            with _utils.shade_exceptions("Error fetching stack"):
+                stacks = [self.manager.submitTask(
+                    _tasks.StackGet(stack_id=name_or_id))]
+            nstacks = _utils.normalize_stacks(stacks)
+            return _utils._filter_list(nstacks, name_or_id, filters)
+
         return _utils._get_entity(
-            self.search_stacks, name_or_id, filters)
+            search_one_stack, name_or_id, filters)
 
     def create_keypair(self, name, public_key):
         """Create a new keypair.

shade/tests/unit/test_stack.py

@@ -149,7 +149,7 @@ class TestStack(base.TestCase):
     @mock.patch.object(shade.OpenStackCloud, 'heat_client')
     def test_get_stack(self, mock_heat):
         stack = fakes.FakeStack('azerty', 'stack',)
-        mock_heat.stacks.list.return_value = [stack]
+        mock_heat.stacks.get.return_value = stack
         res = self.cloud.get_stack('stack')
         self.assertIsNotNone(res)
         self.assertEqual(stack.stack_name, res['stack_name'])