localstack · simonrw · Aug 15, 2025 · Aug 9, 2025 · Aug 9, 2025 · Aug 9, 2025
@@ -257,10 +257,11 @@ def execute_macro(
     formatted_stack_parameters = {}
     for key, value in stack_parameters.items():
         # TODO: we want to support other types of parameters
-        if value.get("ParameterType") == "CommaDelimitedList":
-            formatted_stack_parameters[key] = value.get("ParameterValue").split(",")
+        parameter_value = value.get("ParameterValue")
+        if value.get("ParameterType") == "CommaDelimitedList" and isinstance(parameter_value, str):
+            formatted_stack_parameters[key] = parameter_value.split(",")
         else:
-            formatted_stack_parameters[key] = value.get("ParameterValue")
+            formatted_stack_parameters[key] = parameter_value
 
     transformation_id = f"{account_id}::{macro['Name']}"
     event = {

@@ -660,6 +660,10 @@ def _visit_intrinsic_function(
         arguments = self._visit_value(
             scope=arguments_scope, before_value=before_arguments, after_value=after_arguments
         )
+
+        if intrinsic_function == "Ref" and arguments.value == "AWS::NoValue":
+            arguments.value = Nothing
+
         if is_created(before=before_arguments, after=after_arguments):
             change_type = ChangeType.CREATED
         elif is_removed(before=before_arguments, after=after_arguments):

@@ -924,7 +924,7 @@ def visit_node_parameter(self, node_parameter: NodeParameter) -> PreprocEntityDe
 
         def _resolve_parameter_type(value: str, type_: str) -> Any:
             match type_:
-                case "List<String>":
+                case "List<String>" | "CommaDelimitedList":
                     return [item.strip() for item in value.split(",")]
             return value
 
@@ -965,6 +965,9 @@ def visit_node_intrinsic_function_ref(
         self, node_intrinsic_function: NodeIntrinsicFunction
     ) -> PreprocEntityDelta:
         def _compute_fn_ref(logical_id: str) -> PreprocEntityDelta:
+            if logical_id == "AWS::NoValue":
+                return Nothing
+
             reference_delta: PreprocEntityDelta = self._resolve_reference(logical_id=logical_id)
             if isinstance(before := reference_delta.before, PreprocResource):
                 reference_delta.before = before.physical_resource_id

@@ -1,6 +1,7 @@
 import copy
 import json
 import logging
+import re
 from collections import defaultdict
 from datetime import UTC, datetime
 
@@ -122,6 +123,10 @@
 
 LOG = logging.getLogger(__name__)
 
+SSM_PARAMETER_TYPE_RE = re.compile(
+    r"^AWS::SSM::Parameter::Value<(?P<listtype>List<)?(?P<innertype>[^>]+)>?>$"
+)
+
 
 def is_stack_arn(stack_name_or_id: str) -> bool:
     return ARN_STACK_REGEX.match(stack_name_or_id) is not None
@@ -224,16 +229,30 @@ def _resolve_parameters(
                 type_=parameter["Type"], given_value=given_value, default_value=default_value
             )
 
-            if parameter["Type"] == "AWS::SSM::Parameter::Value<String>":
-                # TODO: support other parameter types
-                try:
-                    resolved_parameter["resolved_value"] = resolve_ssm_parameter(
-                        account_id, region_name, given_value or default_value
-                    )
-                except Exception:
-                    raise ValidationError(
-                        f"Parameter {name} should either have input value or default value"
-                    )
+            # TODO: support other parameter types
+            if match := SSM_PARAMETER_TYPE_RE.match(parameter["Type"]):
+                inner_type = match.group("innertype")
+                is_list_type = match.group("listtype") is not None
+                if is_list_type or inner_type == "CommaDelimitedList":
+                    # list types
+                    try:
+                        resolved_value = resolve_ssm_parameter(
+                            account_id, region_name, given_value or default_value
+                        )
+                        resolved_parameter["resolved_value"] = resolved_value.split(",")
+                    except Exception:
+                        raise ValidationError(
+                            f"Parameter {name} should either have input value or default value"
+                        )
+                else:
+                    try:
+                        resolved_parameter["resolved_value"] = resolve_ssm_parameter(
+                            account_id, region_name, given_value or default_value
+                        )
+                    except Exception:
+                        raise ValidationError(
+                            f"Parameter {name} should either have input value or default value"
+                        )
             elif given_value is None and default_value is None:
                 invalid_parameters.append(name)
                 continue
@@ -609,11 +628,24 @@ def _describe_change_set(
             NotificationARNs=[],
         )
         if change_set.resolved_parameters:
-            result["Parameters"] = [
-                # TODO: add masking support.
-                Parameter(ParameterKey=key, ParameterValue=value)
-                for (key, value) in change_set.resolved_parameters.items()
-            ]
+            result["Parameters"] = self._render_resolved_parameters(change_set.resolved_parameters)
+        return result
+
+    @staticmethod
+    def _render_resolved_parameters(
+        resolved_parameters: dict[str, EngineParameter],
+    ) -> list[Parameter]:
+        result = []
+        for name, resolved_parameter in resolved_parameters.items():
+            parameter = Parameter(
+                ParameterKey=name,
+                ParameterValue=resolved_parameter.get("given_value")
+                or resolved_parameter.get("default_value"),
+            )
+            if resolved_value := resolved_parameter.get("resolved_value"):
+                parameter["ResolvedValue"] = resolved_value
+            result.append(parameter)
+
         return result
 
     @handler("DescribeChangeSet")
@@ -818,8 +850,7 @@ def describe_stacks(
 
         return DescribeStacksOutput(Stacks=describe_stack_output)
 
-    @staticmethod
-    def _describe_stack(stack: Stack) -> ApiStack:
+    def _describe_stack(self, stack: Stack) -> ApiStack:
         stack_description = ApiStack(
             Description=stack.description,
             CreationTime=stack.creation_time,
@@ -835,7 +866,6 @@ def _describe_stack(stack: Stack) -> ApiStack:
             RollbackConfiguration=RollbackConfiguration(),
             Tags=[],
             NotificationARNs=[],
-            # "Parameters": stack.resolved_parameters,
         )
         if stack.status != StackStatus.REVIEW_IN_PROGRESS:
             # TODO: actually track updated time
@@ -847,16 +877,9 @@ def _describe_stack(stack: Stack) -> ApiStack:
             stack_description["ChangeSetId"] = change_set_id
 
         if stack.resolved_parameters:
-            stack_description["Parameters"] = []
-            for name, resolved_parameter in stack.resolved_parameters.items():
-                parameter = Parameter(
-                    ParameterKey=name,
-                    ParameterValue=resolved_parameter.get("given_value")
-                    or resolved_parameter.get("default_value"),
-                )
-                if resolved_value := resolved_parameter.get("resolved_value"):
-                    parameter["ResolvedValue"] = resolved_value
-                stack_description["Parameters"].append(parameter)
+            stack_description["Parameters"] = self._render_resolved_parameters(
+                stack.resolved_parameters
+            )
 
         if stack.resolved_outputs:
             stack_description["Outputs"] = stack.resolved_outputs

@@ -386,7 +386,6 @@ def test_create_change_set_missing_stackname(aws_client):
         )
 
 
-@skip_if_v2_provider("Resolve")
 @markers.aws.validated
 def test_create_change_set_with_ssm_parameter(
     cleanup_changesets,

@@ -122,3 +122,28 @@ def test_resolve_transitive_placeholders_in_strings(deploy_cfn_template, aws_cli
         snapshot.transform.regex(r"/cdk-bootstrap/(\w+)/", "/cdk-bootstrap/.../")
     )
     snapshot.match("tags", tags)
+
+
+@markers.aws.validated
+@pytest.mark.parametrize("parameter_value", ["yes", "no"])
+def test_aws_novalue(deploy_cfn_template, parameter_value):
+    """
+    Test that AWS::NoValue is correctly executed in the CFn engine
+    """
+    fallback_bucket_name = f"my-bucket-{short_uid()}"
+    stack = deploy_cfn_template(
+        template_path=os.path.join(os.path.dirname(__file__), "../../../templates/aws_novalue.yml"),
+        parameters={
+            "SetBucketName": parameter_value,
+            "FallbackBucketName": fallback_bucket_name,
+        },
+    )
+    outputs = stack.outputs
+
+    match parameter_value:
+        case "yes":
+            assert outputs["BucketName"] == fallback_bucket_name
+        case "no":
+            assert outputs["BucketName"] != fallback_bucket_name
+        case other:
+            pytest.fail(f"Test setup error, unexpected parameter value: {other}")
@@ -8,6 +8,24 @@
   "tests/aws/services/cloudformation/engine/test_references.py::TestFnSub::test_non_string_parameter_in_sub": {
     "last_validated_date": "2024-10-17T22:49:56+00:00"
   },
+  "tests/aws/services/cloudformation/engine/test_references.py::test_aws_novalue[no]": {
+    "last_validated_date": "2025-08-12T21:47:08+00:00",
+    "durations_in_seconds": {
+      "setup": 0.0,
+      "call": 22.44,
+      "teardown": 4.36,
+      "total": 26.8
+    }
+  },
+  "tests/aws/services/cloudformation/engine/test_references.py::test_aws_novalue[yes]": {
+    "last_validated_date": "2025-08-12T21:46:41+00:00",
+    "durations_in_seconds": {
+      "setup": 0.0,
+      "call": 23.36,
+      "teardown": 4.36,
+      "total": 27.72
+    }
+  },
   "tests/aws/services/cloudformation/engine/test_references.py::test_resolve_transitive_placeholders_in_strings": {
     "last_validated_date": "2024-06-18T19:55:48+00:00"
   },

@@ -22,7 +22,6 @@ class TestParity:
         - Negative test: missing required properties
     """
 
-    @skip_if_v2_provider("Engine", reason="possible resource dependency issue")
     @markers.aws.validated
     @markers.snapshot.skip_snapshot_verify(
         paths=["$..IsTruncated"]

@@ -2,7 +2,6 @@
 import os
 
 import pytest
-from tests.aws.services.cloudformation.conftest import skip_if_v2_provider
 
 from localstack.services.iam.provider import SERVICE_LINKED_ROLE_PATH_PREFIX
 from localstack.testing.pytest import markers
@@ -202,7 +201,6 @@ def test_update_inline_policy(deploy_cfn_template, snapshot, aws_client):
     snapshot.match("role_updated_inline_policy", role_updated_inline_policy_resource)
 
 
-@skip_if_v2_provider("Engine", reason="Ref: AWS::NoValue")
 @markers.aws.validated
 @markers.snapshot.skip_snapshot_verify(
     paths=[

@@ -350,7 +350,6 @@ def test_create_stack_with_ssm_parameters(
         )
 
     @markers.aws.validated
-    @skip_if_v2_provider("Resolve")
     def test_resolve_ssm(self, create_parameter, deploy_cfn_template):
         parameter_key = f"param-key-{short_uid()}"
         parameter_value = f"param-value-{short_uid()}"
@@ -393,7 +392,6 @@ def test_resolve_ssm_with_version(self, create_parameter, deploy_cfn_template, a
         topic_name = result.outputs["TopicName"]
         assert topic_name == parameter_value_v1
 
-    @skip_if_v2_provider("Resolve")
     @markers.aws.needs_fixing
     def test_resolve_ssm_secure(self, create_parameter, deploy_cfn_template):
         parameter_key = f"param-key-{short_uid()}"
@@ -471,7 +469,6 @@ def test_ssm_nested_with_nested_stack(self, s3_create_bucket, deploy_cfn_templat
 
         assert ssm_parameter == key_value
 
-    @skip_if_v2_provider("Resolve", reason="stringlist type not supported yet")
     @markers.aws.validated
     def test_create_change_set_with_ssm_parameter_list(
         self, deploy_cfn_template, aws_client, region_name, account_id, snapshot

diff --git a/tests/aws/templates/aws_novalue.yml b/tests/aws/templates/aws_novalue.yml
@@ -0,0 +1,22 @@
+Parameters:
+  SetBucketName:
+    Type: String
+  FallbackBucketName:
+    Type: String
+Conditions:
+  ShouldSetBucketName:
+    Fn::Equals:
+      - "yes"
+      - !Ref SetBucketName
+Resources:
+  MyBucket:
+    Type: AWS::S3::Bucket
+    Properties:
+      BucketName:
+        Fn::If:
+          - ShouldSetBucketName
+          - !Ref FallbackBucketName
+          - !Ref AWS::NoValue
+Outputs:
+  BucketName:
+    Value: !Ref MyBucket