[Resolve #915] Support ChangeSetType CREATE (#1469)

This adds logic supporting the case of creating change sets for a stack that does not already exist. That is, it adds support for change sets of ChangeSetType CREATE. https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/cloudformation/client/create_change_set.html

To add some context, there is no obvious reason why Sceptre does not already support change sets of type CREATE since the logic for detecting stack status already exists for the launch command. The project's initial commit already has this inconsistency and essentially the same code. It is probably an oversight.

The changes have already been tested by Rohit S in this Slack thread
https://og-aws.slack.com/archives/C01JNN8RGBB/p1716869822031499

In addition, it is necessary to add logic to handle the REVIEW_IN_PROGRESS state, both for the case of the launch and create action.
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-describing-stacks.html

Creation of a change set on a non-existent stack actually creates a stack and places it into the REVIEW_IN_PROGRESS state. If Sceptre is then to launch this stack, it is necessary to firstly delete the stack, just as it already does in the cases of states CREATE_FAILED and ROLLBACK_COMPLETE.

integration-tests/features/create-change-set.feature

@@ -18,8 +18,7 @@ Feature: Create change set
     Given stack "1/A" does not exist
     and the template for stack "1/A" is "valid_template.json"
     When the user creates change set "A" for stack "1/A"
-    Then a "ClientError" is raised
-    and the user is told "stack does not exist"
+    Then stack "1/A" has change set "A" in "CREATE_COMPLETE" state
 
   Scenario: create new change set with updated template and ignore dependencies
     Given stack "1/A" exists in "CREATE_COMPLETE" state

sceptre/plan/actions.py

@@ -212,7 +212,11 @@ def launch(self) -> StackStatus:
 
         if existing_status == "PENDING":
             status = self.create()
-        elif existing_status in ["CREATE_FAILED", "ROLLBACK_COMPLETE"]:
+        elif existing_status in [
+            "CREATE_FAILED",
+            "ROLLBACK_COMPLETE",
+            "REVIEW_IN_PROGRESS",
+        ]:
             self.delete()
             status = self.create()
         elif existing_status.endswith("COMPLETE"):
@@ -431,6 +435,21 @@ def create_change_set(self, change_set_name):
         :param change_set_name: The name of the Change Set.
         :type change_set_name: str
         """
+        try:
+            existing_status = self._get_status()
+        except StackDoesNotExistError:
+            existing_status = "PENDING"
+
+        self.logger.info(
+            "%s - Stack is in the %s state", self.stack.name, existing_status
+        )
+
+        change_set_type = (
+            "CREATE"
+            if existing_status in ["PENDING", "REVIEW_IN_PROGRESS"]
+            else "UPDATE"
+        )
+
         create_change_set_kwargs = {
             "StackName": self.stack.external_name,
             "Parameters": self._format_parameters(self.stack.parameters),
@@ -440,6 +459,7 @@ def create_change_set(self, change_set_name):
                 "CAPABILITY_AUTO_EXPAND",
             ],
             "ChangeSetName": change_set_name,
+            "ChangeSetType": change_set_type,
             "NotificationARNs": self.stack.notifications,
             "Tags": [
                 {"Key": str(k), "Value": str(v)} for k, v in self.stack.tags.items()

tests/test_actions.py

@@ -397,6 +397,19 @@ def test_launch_with_stack_that_failed_to_create(
         mock_create.assert_called_once_with()
         assert response == sentinel.launch_response
 
+    @patch("sceptre.plan.actions.StackActions.create")
+    @patch("sceptre.plan.actions.StackActions.delete")
+    @patch("sceptre.plan.actions.StackActions._get_status")
+    def test_launch_with_stack_in_review_in_progress(
+        self, mock_get_status, mock_delete, mock_create
+    ):
+        mock_get_status.return_value = "REVIEW_IN_PROGRESS"
+        mock_create.return_value = sentinel.launch_response
+        response = self.actions.launch()
+        mock_delete.assert_called_once_with()
+        mock_create.assert_called_once_with()
+        assert response == sentinel.launch_response
+
     @patch("sceptre.plan.actions.StackActions.update")
     @patch("sceptre.plan.actions.StackActions._get_status")
     def test_launch_with_complete_stack_with_updates_to_perform(
@@ -632,6 +645,7 @@ def test_create_change_set_sends_correct_request(self):
                     "CAPABILITY_AUTO_EXPAND",
                 ],
                 "ChangeSetName": sentinel.change_set_name,
+                "ChangeSetType": "UPDATE",
                 "RoleARN": sentinel.cloudformation_service_role,
                 "NotificationARNs": [sentinel.notification],
                 "Tags": [{"Key": "tag1", "Value": "val1"}],
@@ -659,12 +673,38 @@ def test_create_change_set_sends_correct_request_no_notifications(self):
                     "CAPABILITY_AUTO_EXPAND",
                 ],
                 "ChangeSetName": sentinel.change_set_name,
+                "ChangeSetType": "UPDATE",
                 "RoleARN": sentinel.cloudformation_service_role,
                 "NotificationARNs": [],
                 "Tags": [{"Key": "tag1", "Value": "val1"}],
             },
         )
 
+    @patch("sceptre.plan.actions.StackActions._get_status")
+    def test_create_change_set_with_non_existent_stack(self, mock_get_status):
+        mock_get_status.side_effect = StackDoesNotExistError()
+        self.template._body = sentinel.template
+        self.actions.create_change_set(sentinel.change_set_name)
+        self.actions.connection_manager.call.assert_called_with(
+            service="cloudformation",
+            command="create_change_set",
+            kwargs={
+                "StackName": sentinel.external_name,
+                "TemplateBody": sentinel.template,
+                "Parameters": [{"ParameterKey": "key1", "ParameterValue": "val1"}],
+                "Capabilities": [
+                    "CAPABILITY_IAM",
+                    "CAPABILITY_NAMED_IAM",
+                    "CAPABILITY_AUTO_EXPAND",
+                ],
+                "ChangeSetName": sentinel.change_set_name,
+                "ChangeSetType": "CREATE",
+                "RoleARN": sentinel.cloudformation_service_role,
+                "NotificationARNs": [sentinel.notification],
+                "Tags": [{"Key": "tag1", "Value": "val1"}],
+            },
+        )
+
     def test_delete_change_set_sends_correct_request(self):
         self.actions.delete_change_set(sentinel.change_set_name)
         self.actions.connection_manager.call.assert_called_with(