localstack · MEPalma · May 19, 2025 · May 7, 2025 · May 7, 2025 · May 7, 2025
@@ -7,7 +7,6 @@
 from localstack.services.cloudformation.engine.v2.change_set_model import (
     NodeIntrinsicFunction,
     NodeResource,
-    NodeTemplate,
     PropertiesKey,
 )
 from localstack.services.cloudformation.engine.v2.change_set_model_preproc import (
@@ -16,6 +15,7 @@
     PreprocProperties,
     PreprocResource,
 )
+from localstack.services.cloudformation.v2.entities import ChangeSet
 
 CHANGESET_KNOWN_AFTER_APPLY: Final[str] = "{{changeSet:KNOWN_AFTER_APPLY}}"
 
@@ -26,13 +26,10 @@ class ChangeSetModelDescriber(ChangeSetModelPreproc):
 
     def __init__(
         self,
-        node_template: NodeTemplate,
-        before_resolved_resources: dict,
+        change_set: ChangeSet,
         include_property_values: bool,
     ):
-        super().__init__(
-            node_template=node_template, before_resolved_resources=before_resolved_resources
-        )
+        super().__init__(change_set=change_set)
         self._include_property_values = include_property_values
         self._changes = list()
 

@@ -38,18 +38,13 @@ class ChangeSetModelExecutorResult:
 
 
 class ChangeSetModelExecutor(ChangeSetModelPreproc):
-    _change_set: Final[ChangeSet]
     # TODO: add typing for resolved resources and parameters.
     resources: Final[dict]
     outputs: Final[dict]
     resolved_parameters: Final[dict]
 
     def __init__(self, change_set: ChangeSet):
-        super().__init__(
-            node_template=change_set.update_graph,
-            before_resolved_resources=change_set.stack.resolved_resources,
-        )
-        self._change_set = change_set
+        super().__init__(change_set=change_set)
         self.resources = dict()
         self.outputs = dict()
         self.resolved_parameters = dict()

@@ -28,6 +28,22 @@
 from localstack.services.cloudformation.engine.v2.change_set_model_visitor import (
     ChangeSetModelVisitor,
 )
+from localstack.services.cloudformation.v2.entities import ChangeSet
+from localstack.utils.aws.arns import get_partition
+from localstack.utils.urls import localstack_host
+
+_AWS_URL_SUFFIX = localstack_host().host  # The value in AWS is "amazonaws.com"
+
+_PSEUDO_PARAMETERS: Final[set[str]] = {
+    "AWS::Partition",
+    "AWS::AccountId",
+    "AWS::Region",
+    "AWS::StackName",
+    "AWS::StackId",
+    "AWS::URLSuffix",
+    "AWS::NoValue",
+    "AWS::NotificationARNs",
+}
 
 TBefore = TypeVar("TBefore")
 TAfter = TypeVar("TAfter")
@@ -126,13 +142,15 @@ def __eq__(self, other):
 
 
 class ChangeSetModelPreproc(ChangeSetModelVisitor):
+    _change_set: Final[ChangeSet]
     _node_template: Final[NodeTemplate]
     _before_resolved_resources: Final[dict]
     _processed: dict[Scope, Any]
 
-    def __init__(self, node_template: NodeTemplate, before_resolved_resources: dict):
-        self._node_template = node_template
-        self._before_resolved_resources = before_resolved_resources
+    def __init__(self, change_set: ChangeSet):
+        self._change_set = change_set
+        self._node_template = change_set.update_graph
+        self._before_resolved_resources = change_set.stack.resolved_resources
         self._processed = dict()
 
     def process(self) -> None:
@@ -157,11 +175,20 @@ def _get_node_property_for(
                 return node_property
         return None
 
-    @staticmethod
     def _deployed_property_value_of(
-        resource_logical_id: str, property_name: str, resolved_resources: dict
+        self, resource_logical_id: str, property_name: str, resolved_resources: dict
     ) -> Any:
         # TODO: typing around resolved resources is needed and should be reflected here.
+
+        # Before we can obtain deployed value for a resource, we need to first ensure to
+        # process the resource if this wasn't processed already. Ideally, values should only
+        # be accessible through delta objects, to ensure computation is always complete at
+        # every level.
+        node_resource = self._get_node_resource_for(
+            resource_name=resource_logical_id, node_template=self._node_template
+        )
+        self.visit(node_resource)
+
         resolved_resource = resolved_resources.get(resource_logical_id)
         if resolved_resource is None:
             raise RuntimeError(
@@ -223,7 +250,38 @@ def _resolve_condition(self, logical_id: str) -> PreprocEntityDelta:
             return condition_delta
         raise RuntimeError(f"No condition '{logical_id}' was found.")
 
+    def _resolve_pseudo_parameter(self, pseudo_parameter_name: str) -> PreprocEntityDelta:
+        match pseudo_parameter_name:
+            case "AWS::Partition":
+                after = get_partition(self._change_set.region_name)
+            case "AWS::AccountId":
+                after = self._change_set.stack.account_id
+            case "AWS::Region":
+                after = self._change_set.stack.region_name
+            case "AWS::StackName":
+                after = self._change_set.stack.stack_name
+            case "AWS::StackId":
+                after = self._change_set.stack.stack_id
+            case "AWS::URLSuffix":
+                after = _AWS_URL_SUFFIX
+            case "AWS::NoValue":
+                # TODO: add support for NoValue, None cannot be used to communicate a Null value in preproc classes.
+                raise NotImplementedError("The use of AWS:NoValue is currently unsupported")
+            case "AWS::NotificationARNs":
+                raise NotImplementedError(
+                    "The use of AWS::NotificationARNs is currently unsupported"
+                )
+            case _:
+                raise RuntimeError(f"Unknown pseudo parameter value '{pseudo_parameter_name}'")
+        return PreprocEntityDelta(before=after, after=after)
+
     def _resolve_reference(self, logical_id: str) -> PreprocEntityDelta:
+        if logical_id in _PSEUDO_PARAMETERS:
+            pseudo_parameter_delta = self._resolve_pseudo_parameter(
+                pseudo_parameter_name=logical_id
+            )
+            return pseudo_parameter_delta
+
         node_parameter = self._get_node_parameter_if_exists(parameter_name=logical_id)
         if isinstance(node_parameter, NodeParameter):
             parameter_delta = self.visit(node_parameter)

@@ -2,11 +2,9 @@
 from typing import TypedDict
 
 from localstack.aws.api.cloudformation import (
-    Changes,
     ChangeSetStatus,
     ChangeSetType,
     CreateChangeSetInput,
-    DescribeChangeSetOutput,
     ExecutionStatus,
     Output,
     Parameter,
@@ -26,9 +24,6 @@
     ChangeSetModel,
     NodeTemplate,
 )
-from localstack.services.cloudformation.engine.v2.change_set_model_describer import (
-    ChangeSetModelDescriber,
-)
 from localstack.utils.aws import arns
 from localstack.utils.strings import short_uid
 
@@ -187,35 +182,3 @@ def populate_update_graph(
             after_parameters=after_parameters,
         )
         self.update_graph = change_set_model.get_update_model()
-
-    def describe_details(self, include_property_values: bool) -> DescribeChangeSetOutput:
-        change_set_describer = ChangeSetModelDescriber(
-            node_template=self.update_graph,
-            before_resolved_resources=self.stack.resolved_resources,
-            include_property_values=include_property_values,
-        )
-        changes: Changes = change_set_describer.get_changes()
-
-        result = {
-            "Status": self.status,
-            "ChangeSetType": self.change_set_type,
-            "ChangeSetId": self.change_set_id,
-            "ChangeSetName": self.change_set_name,
-            "ExecutionStatus": self.execution_status,
-            "RollbackConfiguration": {},
-            "StackId": self.stack.stack_id,
-            "StackName": self.stack.stack_name,
-            "StackStatus": self.stack.status,
-            "CreationTime": self.creation_time,
-            "LastUpdatedTime": "",
-            "DisableRollback": "",
-            "EnableTerminationProtection": "",
-            "Transform": "",
-            # TODO: mask no echo
-            "Parameters": [
-                Parameter(ParameterKey=key, ParameterValue=value)
-                for (key, value) in self.stack.resolved_parameters.items()
-            ],
-            "Changes": changes,
-        }
-        return result
@@ -3,6 +3,7 @@
 
 from localstack.aws.api import RequestContext, handler
 from localstack.aws.api.cloudformation import (
+    Changes,
     ChangeSetNameOrId,
     ChangeSetNotFoundException,
     ChangeSetStatus,
@@ -24,12 +25,16 @@
     RetainExceptOnCreate,
     RetainResources,
     RoleARN,
+    RollbackConfiguration,
     StackName,
     StackNameOrId,
     StackStatus,
 )
 from localstack.services.cloudformation import api_utils
 from localstack.services.cloudformation.engine import template_preparer
+from localstack.services.cloudformation.engine.v2.change_set_model_describer import (
+    ChangeSetModelDescriber,
+)
 from localstack.services.cloudformation.engine.v2.change_set_model_executor import (
     ChangeSetModelExecutor,
 )
@@ -296,6 +301,32 @@ def _run(*args):
 
         return ExecuteChangeSetOutput()
 
+    def _describe_change_set(
+        self, change_set: ChangeSet, include_property_values: bool
+    ) -> DescribeChangeSetOutput:
+        change_set_describer = ChangeSetModelDescriber(
+            change_set=change_set, include_property_values=include_property_values
+        )
+        changes: Changes = change_set_describer.get_changes()
+
+        result = DescribeChangeSetOutput(
+            Status=change_set.status,
+            ChangeSetId=change_set.change_set_id,
+            ChangeSetName=change_set.change_set_name,
+            ExecutionStatus=change_set.execution_status,
+            RollbackConfiguration=RollbackConfiguration(),
+            StackId=change_set.stack.stack_id,
+            StackName=change_set.stack.stack_name,
+            CreationTime=change_set.creation_time,
+            Parameters=[
+                # TODO: add masking support.
+                Parameter(ParameterKey=key, ParameterValue=value)
+                for (key, value) in change_set.stack.resolved_parameters.items()
+            ],
+            Changes=changes,
+        )
+        return result
+
     @handler("DescribeChangeSet")
     def describe_change_set(
         self,
@@ -312,9 +343,8 @@ def describe_change_set(
         change_set = find_change_set_v2(state, change_set_name, stack_name)
         if not change_set:
             raise ChangeSetNotFoundException(f"ChangeSet [{change_set_name}] does not exist")
-
-        result = change_set.describe_details(
-            include_property_values=include_property_values or False
+        result = self._describe_change_set(
+            change_set=change_set, include_property_values=include_property_values or False
         )
         return result
 

@@ -59,8 +59,8 @@
 """
 
 
+@pytest.mark.skip(reason="no support for DependsOn")
 # this is an `only_localstack` test because it makes use of _custom_id_ tag
-@pytest.mark.skip(reason="no support for pseudo-parameters")
 @markers.aws.only_localstack
 def test_cfn_apigateway_aws_integration(deploy_cfn_template, aws_client):
     api_name = f"rest-api-{short_uid()}"
@@ -143,7 +143,7 @@ def test_cfn_apigateway_swagger_import(deploy_cfn_template, echo_http_server_pos
     assert content["url"].endswith("/post")
 
 
-@pytest.mark.skip(reason="No support for pseudo-parameters")
+@pytest.mark.skip(reason="No support for DependsOn")
 @markers.aws.only_localstack
 def test_url_output(httpserver, deploy_cfn_template):
     httpserver.expect_request("").respond_with_data(b"", 200)
@@ -396,7 +396,6 @@ def test_cfn_apigateway_rest_api(deploy_cfn_template, aws_client):
     # assert not apis
 
 
-@pytest.mark.skip(reason="no support for pseudo-parameters")
 @markers.aws.validated
 def test_account(deploy_cfn_template, aws_client):
     stack = deploy_cfn_template(

@@ -309,3 +309,40 @@ def test_immutable_property_update_causes_resource_replacement(
             }
         }
         capture_update_process(snapshot, template_1, template_2)
+
+    @markers.aws.validated
+    def test_supported_pseudo_parameter(
+        self,
+        snapshot,
+        capture_update_process,
+    ):
+        topic_name_1 = f"topic-name-1-{long_uid()}"
+        snapshot.add_transformer(RegexTransformer(topic_name_1, "topic_name_1"))
+        topic_name_2 = f"topic-name-2-{long_uid()}"
+        snapshot.add_transformer(RegexTransformer(topic_name_2, "topic_name_2"))
+        snapshot.add_transformer(RegexTransformer("amazonaws.com", "url_suffix"))
+        snapshot.add_transformer(RegexTransformer("localhost.localstack.cloud", "url_suffix"))
+        template_1 = {
+            "Resources": {
+                "Topic1": {"Type": "AWS::SNS::Topic", "Properties": {"TopicName": topic_name_1}},
+            }
+        }
+        template_2 = {
+            "Resources": {
+                "Topic2": {
+                    "Type": "AWS::SNS::Topic",
+                    "Properties": {
+                        "TopicName": topic_name_2,
+                        "Tags": [
+                            {"Key": "Partition", "Value": {"Ref": "AWS::Partition"}},
+                            {"Key": "AccountId", "Value": {"Ref": "AWS::AccountId"}},
+                            {"Key": "Region", "Value": {"Ref": "AWS::Region"}},
+                            {"Key": "StackName", "Value": {"Ref": "AWS::StackName"}},
+                            {"Key": "StackId", "Value": {"Ref": "AWS::StackId"}},
+                            {"Key": "URLSuffix", "Value": {"Ref": "AWS::URLSuffix"}},
+                        ],
+                    },
+                },
+            }
+        }
+        capture_update_process(snapshot, template_1, template_2)