Make get_attr consistent across template versions

Several changes to when get_attr returns None as a placeholder were made
to the original version of HOT but not reflected in later versions. The
missing changes were:

- I1b2b4f0e967695cf3297d93022cecec958e94b24 (The fix for bug 1333208.)

- I6dbaa7ee4e9d534c31823b4812efcb387c695a22 (The implementation of the
  blueprint convergence-lightweight-stack. The lack of this suggests
  that our stacks may be less lightweight in practice than we thought.)

- I2bfac4ce6a8806acc85c17466429d63a5d93d79f (A small change to the
  previous patch.)

- I84762de87032168f97cdd19533649851073b4e81 (Part of the fix for
  bug 1486281)

This change refactors the classes such that new and old versions of the
templates share a single implementation of this test, so there should be
no future opportunity for them to get out of sync.

Change-Id: I367ba6abe5c0176ff84ec676a42e9329cf84b48e
Closes-Bug: #1623707

1 files changed, 17 insertions, 12 deletions

diff --git a/heat/engine/hot/functions.py b/heat/engine/hot/functions.py
index 0b9e8277f..559203237 100644
--- a/heat/engine/hot/functions.py
+++ b/heat/engine/hot/functions.py
@@ -212,17 +212,24 @@ class GetAttThenSelect(function.Function):
             raise exception.InvalidTemplateAttribute(
                 resource=self._resource_name, key=attr)
 
-    def result(self):
-        attr_name = function.resolve(self._attribute)
-
-        r = self._resource()
+    def _result_ready(self, r):
         if r.action in (r.CREATE, r.ADOPT, r.SUSPEND, r.RESUME,
                         r.UPDATE, r.ROLLBACK, r.SNAPSHOT, r.CHECK):
-            attribute = r.FnGetAtt(attr_name)
+            return True
+
         # NOTE(sirushtim): Add r.INIT to states above once convergence
         # is the default.
-        elif r.stack.has_cache_data(r.name) and r.action == r.INIT:
-            attribute = r.FnGetAtt(attr_name)
+        if r.stack.has_cache_data(r.name) and r.action == r.INIT:
+            return True
+
+        return False
+
+    def result(self):
+        attr_name = function.resolve(self._attribute)
+
+        resource = self._resource()
+        if self._result_ready(resource):
+            attribute = resource.FnGetAtt(attr_name)
         else:
             attribute = None
 
@@ -249,11 +256,9 @@ class GetAtt(GetAttThenSelect):
         path_components = function.resolve(self._path_components)
         attribute = function.resolve(self._attribute)
 
-        r = self._resource()
-        if (r.status in (r.IN_PROGRESS, r.COMPLETE) and
-                r.action in (r.CREATE, r.ADOPT, r.SUSPEND, r.RESUME,
-                             r.UPDATE, r.CHECK, r.SNAPSHOT)):
-            return r.FnGetAtt(attribute, *path_components)
+        resource = self._resource()
+        if self._result_ready(resource):
+            return resource.FnGetAtt(attribute, *path_components)
         else:
             return None