Fix not correct AWS::StackId value

Add call of method _set_param_stackid() to method update_task() in class
parser.Stack. This ensures that an updated stack still has the right
AWS::StackId param.
Add a unit test for this case.

Change-Id: I0d28346631546577a85735292a24c2512476d4b4
Closes-Bug: #1240888

heat/engine/parser.py

@@ -486,6 +486,7 @@ def update_task(self, newstack, action=UPDATE):
 
             self.env = newstack.env
             self.parameters = newstack.parameters
+            self._set_param_stackid()
 
             try:
                 updater.start(timeout=self.timeout_secs())

heat/tests/test_parser.py

@@ -763,6 +763,37 @@ def test_set_param_id(self):
                          identifier.arn())
         self.m.VerifyAll()
 
+    @utils.stack_delete_after
+    def test_set_param_id_update(self):
+        tmpl = {'Resources': {
+                'AResource': {'Type': 'ResourceWithPropsType',
+                              'Metadata': {'Bar': {'Ref': 'AWS::StackId'}},
+                              'Properties': {'Foo': 'abc'}}}}
+
+        self.stack = parser.Stack(self.ctx, 'update_stack_arn_test',
+                                  template.Template(tmpl))
+        self.stack.store()
+        self.stack.create()
+        self.assertEqual(self.stack.state,
+                         (parser.Stack.CREATE, parser.Stack.COMPLETE))
+
+        stack_arn = self.stack.parameters['AWS::StackId']
+
+        tmpl2 = {'Resources': {
+                 'AResource': {'Type': 'ResourceWithPropsType',
+                               'Metadata': {'Bar': {'Ref': 'AWS::StackId'}},
+                               'Properties': {'Foo': 'xyz'}}}}
+
+        updated_stack = parser.Stack(self.ctx, 'updated_stack',
+                                     template.Template(tmpl2))
+
+        self.stack.update(updated_stack)
+        self.assertEqual(self.stack.state,
+                         (parser.Stack.UPDATE, parser.Stack.COMPLETE))
+        self.assertEqual(self.stack['AResource'].properties['Foo'], 'xyz')
+
+        self.assertEqual(self.stack['AResource'].metadata['Bar'], stack_arn)
+
     @utils.stack_delete_after
     def test_load_param_id(self):
         self.stack = parser.Stack(self.ctx, 'param_load_arn_test',