Stack preview fails for scaling groups with Template version was not provided

[William C. Arnold]

Exception logged in screen-h-api.log is
2014-07-31 19:10:54.162 29106 WARNING oslo.messaging._drivers.amqpdriver [req-9e945e84-c08d-4ebe-b573-42a547925a42 ] No calling threads waiting for msg_id : 83c7257b7e1544cabe13a4ca1aca62fc, message : {u\
'_unique_id': u'ae2b95e1d8bf4ef6bd5ed790e87e4a97', u'failure': u'{"args": [], "module": "heat.common.exception", "kwargs": {"explanation": "Template version was not provided"}, "message": "The template v\
ersion is invalid: Template version was not provided", "tb": ["Traceback (most recent call last):\\n", " File \\"/opt/stack/heat/heat/engine/service.py\\", line 63, in wrapped\\n return func(self, ct\
x, *args, **kwargs)\\n", " File \\"/opt/stack/heat/heat/engine/service.py\\", line 539, in preview_stack\\n return api.format_stack_preview(stack)\\n", " File \\"/opt/stack/heat/heat/engine/api.py\\\
", line 169, in format_stack_preview\\n fmt_resources = map(format_resource, stack.preview_resources())\\n", " File \\"/opt/stack/heat/heat/engine/stack.py\\", line 509, in preview_resources\\n fo\
r resource in self.resources.itervalues()]\\n", " File \\"/opt/stack/heat/heat/engine/stack_resource.py\\", line 102, in preview\\n template = parser.Template(self.child_template())\\n", " File \\"/\
opt/stack/heat/heat/engine/template.py\\", line 121, in __new__\\n TemplateClass = get_template_class(cls._plugins, template)\\n", " File \\"/opt/stack/heat/heat/engine/template.py\\", line 90, in ge\
t_template_class\\n version = get_version(template_data, available_versions)\\n", " File \\"/opt/stack/heat/heat/engine/template.py\\", line 73, in get_version\\n explanation = _(\'Template versio\
n was not provided\')\\n", "InvalidTemplateVersion: The template version is invalid: Template version was not provided\\n"], "class": "InvalidTemplateVersion"}', u'result': None}

The immediate cause appears to be that heat/engine/template.py, method get_version(template_data, available_versions):
when operating on the the nested stack, is being passed a heat.engine.cfn.template.CfnTemplate for template_data when it expect a dict.

[William C. Arnold (barnold-8)]

The following (crude) patch works and causes no obvious problems. Will submit as a patch to gerrit.
diff --git a/heat/engine/template.py b/heat/engine/template.py
index c26bebe..e1d26a1 100644
--- a/heat/engine/template.py
+++ b/heat/engine/template.py
@@ -56,6 +56,8 @@ class TemplatePluginManager(object):

 def get_version(template_data, available_versions):
+ if isinstance(template_data, Template):
+ template_data = template_data.t
     version_keys = set(key for key, version in available_versions)
     candidate_keys = set(k for k, v in template_data.iteritems() if
                          isinstance(v, basestring))

[William C. Arnold (barnold-8)]

To replicate using a template found in heat-templates
[x]:~/heat-templates$ heat stack-preview -f cfn/F17/InstanceGroup.template IG -P KeyName=mykey
ERROR: The template version is invalid: Template version was not provided

(With a 2014/08/01 devstack install.)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/111348

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/111348
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=0fc185a962cbde1f5cb0de0fda8c4b15c2ba5eac
Submitter: Jenkins
Branch: master

commit 0fc185a962cbde1f5cb0de0fda8c4b15c2ba5eac
Author: Bill Arnold <email address hidden>
Date: Tue Aug 12 09:12:12 2014 -0400

    Template get_version breaks with Template object

    The get_version method on template expects a dict, breaking
    stack preview. This patch modifies StackResource preview
    to always call the Template constructor with a dict

    Change-Id: I6e75a78b4d496e235f11ec3d94ee58a069ab5336
    Closes-bug: #1351005