Allow a resource to be added to a template

Add a method that allows a ResourceDefinition to be inserted into an
existing template.

Change-Id: Ia418127d72d26a77d731f93cc0eb3a45d983cc82

heat/engine/cfn/template.py

@@ -128,6 +128,25 @@ class CfnTemplate(template.Template):
         resources = self.t.get(self.RESOURCES, {}).items()
         return dict(rsrc_defn_item(name, data) for name, data in resources)
 
+    def add_resource(self, definition, name=None):
+        if name is None:
+            name = definition.name
+        hot_tmpl = definition.render_hot()
+
+        HOT_TO_CFN_ATTRS = {'type': RES_TYPE,
+                            'properties': RES_PROPERTIES,
+                            'metadata': RES_METADATA,
+                            'depends_on': RES_DEPENDS_ON,
+                            'deletion_policy': RES_DELETION_POLICY,
+                            'update_policy': RES_UPDATE_POLICY}
+
+        cfn_tmpl = dict((HOT_TO_CFN_ATTRS[k], v) for k, v in hot_tmpl.items())
+
+        if len(cfn_tmpl.get(RES_DEPENDS_ON, [])) == 1:
+            cfn_tmpl[RES_DEPENDS_ON] = cfn_tmpl[RES_DEPENDS_ON][0]
+
+        self.t.setdefault(self.RESOURCES, {})[name] = cfn_tmpl
+
 
 def template_mapping():
     return {

heat/engine/hot/template.py

@@ -217,6 +217,12 @@ class HOTemplate(template.Template):
         resources = self.t.get(self.RESOURCES, {}).items()
         return dict(rsrc_defn_item(name, data) for name, data in resources)
 
+    def add_resource(self, definition, name=None):
+        if name is None:
+            name = definition.name
+
+        self.t.setdefault(self.RESOURCES, {})[name] = definition.render_hot()
+
 
 def template_mapping():
     return {

heat/engine/template.py

@@ -166,6 +166,15 @@ class Template(collections.Mapping):
         '''Return a dictionary of ResourceDefinition objects.'''
         pass
 
+    @abc.abstractmethod
+    def add_resource(self, definition, name=None):
+        '''Add a resource to the template.
+
+        The resource is passed as a ResourceDefinition object. If no name is
+        specified, the name from the ResourceDefinition should be used.
+        '''
+        pass
+
     def functions(self):
         '''Return a dict of template functions keyed by name.'''
         if self.version not in self._functionmaps:

heat/tests/test_hot.py

@@ -11,6 +11,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import copy
 import six
 
 from heat.common import exception
@@ -616,6 +617,31 @@ class HOTemplateTest(HeatTestCase):
                              parent_resource=parent_resource)
         self.assertEqual('Delete', self.resolve(snippet, stack.t, stack))
 
+    def test_add_resource(self):
+        hot_tpl = template_format.parse('''
+        heat_template_version: 2013-05-23
+        resources:
+          resource1:
+            type: AWS::EC2::Instance
+            properties:
+              property1: value1
+            metadata:
+              foo: bar
+            depends_on:
+              - dummy
+            deletion_policy: Retain
+            update_policy:
+              foo: bar
+        ''')
+        source = parser.Template(hot_tpl)
+        empty = parser.Template(copy.deepcopy(hot_tpl_empty))
+        stack = parser.Stack(utils.dummy_context(), 'test_stack', source)
+
+        for defn in source.resource_definitions(stack).values():
+            empty.add_resource(defn)
+
+        self.assertEqual(hot_tpl['resources'], empty.t['resources'])
+
 
 class StackTest(test_parser.StackTest):
     """Test stack function when stack was created from HOT template."""

heat/tests/test_parser.py

@@ -619,6 +619,30 @@ Mappings:
         self.assertEqual(expected_description, tmpl['Description'])
         self.assertNotIn('Parameters', tmpl.keys())
 
+    def test_add_resource(self):
+        cfn_tpl = template_format.parse('''
+        AWSTemplateFormatVersion: 2010-09-09
+        Resources:
+          resource1:
+            Type: AWS::EC2::Instance
+            Properties:
+              property1: value1
+            Metadata:
+              foo: bar
+            DependsOn: dummy
+            DeletionPolicy: Retain
+            UpdatePolicy:
+              foo: bar
+        ''')
+        source = parser.Template(cfn_tpl)
+        empty = parser.Template(copy.deepcopy(empty_template))
+        stack = parser.Stack(self.ctx, 'test_stack', source)
+
+        for defn in source.resource_definitions(stack).values():
+            empty.add_resource(defn)
+
+        self.assertEqual(cfn_tpl['Resources'], empty.t['Resources'])
+
 
 class TemplateFnErrorTest(HeatTestCase):
     scenarios = [