localstack · simonrw · Oct 8, 2025 · Oct 6, 2025 · Oct 6, 2025 · Oct 6, 2025
@@ -20,6 +20,7 @@
     PreprocResource,
 )
 from localstack.services.cloudformation.v2.entities import ChangeSet
+from localstack.utils.numbers import is_number
 
 CHANGESET_KNOWN_AFTER_APPLY: Final[str] = "{{changeSet:KNOWN_AFTER_APPLY}}"
 
@@ -96,6 +97,19 @@ def _resolve_attribute(self, arguments: str | list[str], select_before: bool) ->
 
         return value
 
+    def visit_node_intrinsic_function(self, node_intrinsic_function: NodeIntrinsicFunction):
+        """
+        Intrinsic function results are always strings when referring to the describe output
+        """
+        # TODO: what about other places?
+        # TODO: should this be put in the preproc?
+        delta = super().visit_node_intrinsic_function(node_intrinsic_function)
+        if is_number(delta.before):
+            delta.before = str(delta.before)
+        if is_number(delta.after):
+            delta.after = str(delta.after)
+        return delta
+
     def visit_node_intrinsic_function_fn_join(
         self, node_intrinsic_function: NodeIntrinsicFunction
     ) -> PreprocEntityDelta:

@@ -56,6 +56,7 @@
 from localstack.services.cloudformation.v2.entities import ChangeSet
 from localstack.services.cloudformation.v2.types import ResolvedResource
 from localstack.utils.aws.arns import get_partition
+from localstack.utils.numbers import to_number
 from localstack.utils.objects import get_value_from_path
 from localstack.utils.run import to_str
 from localstack.utils.strings import to_bytes
@@ -1029,6 +1030,9 @@ def _resolve_parameter_type(value: str, type_: str) -> Any:
             match type_:
                 case "List<String>" | "CommaDelimitedList":
                     return [item.strip() for item in value.split(",")]
+                case "Number":
+                    # TODO: validate the parameter type at template parse time (or whatever is in parity with AWS) so we know this cannot fail
+                    return to_number(value)
             return value
 
         if not is_nothing(after):

@@ -120,9 +120,10 @@
     StackInstance,
     StackSet,
 )
-from localstack.services.cloudformation.v2.types import EngineParameter
+from localstack.services.cloudformation.v2.types import EngineParameter, engine_parameter_value
 from localstack.services.plugins import ServiceLifecycleHook
 from localstack.utils.collections import select_attributes
+from localstack.utils.numbers import is_number
 from localstack.utils.strings import short_uid
 from localstack.utils.threads import start_worker_thread
 
@@ -262,6 +263,12 @@ def _resolve_parameters(
                 no_echo=parameter.get("NoEcho"),
             )
 
+            # validate the type
+            if parameter["Type"] == "Number" and not is_number(
+                engine_parameter_value(resolved_parameter)
+            ):
+                raise ValidationError(f"Parameter '{name}' must be a number.")
+
             # TODO: support other parameter types
             if match := SSM_PARAMETER_TYPE_RE.match(parameter["Type"]):
                 inner_type = match.group("innertype")

diff --git a/localstack-core/localstack/utils/numbers.py b/localstack-core/localstack/utils/numbers.py
@@ -11,6 +11,13 @@ def format_number(number: float, decimals: int = 2):
 
 
 def is_number(s: Any) -> bool:
+    # booleans inherit from int
+    #
+    # >>> a.__class__.__mro__
+    # (<class 'bool'>, <class 'int'>, <class 'object'>)
+    if s is False or s is True:
+        return False
+
     try:
         float(s)  # for int, long and float
         return True

@@ -1,6 +1,11 @@
 import os.path
 
+import pytest
+from tests.aws.services.cloudformation.conftest import skip_if_legacy_engine
+
 from localstack.testing.pytest import markers
+from localstack.testing.pytest.fixtures import StackDeployError
+from localstack.utils.strings import short_uid
 
 
 @markers.aws.validated
@@ -47,3 +52,26 @@ def test_cfn_handle_log_group_resource(deploy_cfn_template, aws_client, snapshot
     stack.destroy()
     response = aws_client.logs.describe_log_groups(logGroupNamePrefix=log_group_prefix)
     assert len(response["logGroups"]) == 0
+
+
+@markers.aws.validated
+@skip_if_legacy_engine()
+def test_handle_existing_log_group(deploy_cfn_template, aws_client, snapshot, cleanups):
+    snapshot.add_transformer(snapshot.transform.cloudformation_api())
+    snapshot.add_transformer(snapshot.transform.key_value("ParameterValue"))
+
+    log_group_name = f"logs-{short_uid()}"
+
+    # create the log group
+    aws_client.logs.create_log_group(logGroupName=log_group_name)
+    cleanups.append(lambda: aws_client.logs.delete_log_group(logGroupName=log_group_name))
+
+    with pytest.raises(StackDeployError) as exc_info:
+        deploy_cfn_template(
+            template_path=os.path.join(
+                os.path.dirname(__file__), "../../../templates/logs_group.yml"
+            ),
+            parameters={"LogGroupName": log_group_name},
+        )
+
+    snapshot.match("failed-stack-describe", exc_info.value.describe_result)
@@ -38,5 +38,37 @@
         }
       }
     }
+  },
+  "tests/aws/services/cloudformation/resources/test_logs.py::test_handle_existing_log_group": {
+    "recorded-date": "06-10-2025, 16:24:57",
+    "recorded-content": {
+      "failed-stack-describe": {
+        "Capabilities": [
+          "CAPABILITY_AUTO_EXPAND",
+          "CAPABILITY_IAM",
+          "CAPABILITY_NAMED_IAM"
+        ],
+        "CreationTime": "datetime",
+        "DeletionTime": "datetime",
+        "DisableRollback": false,
+        "DriftInformation": {
+          "StackDriftStatus": "NOT_CHECKED"
+        },
+        "EnableTerminationProtection": false,
+        "LastUpdatedTime": "datetime",
+        "NotificationARNs": [],
+        "Parameters": [
+          {
+            "ParameterKey": "LogGroupName",
+            "ParameterValue": "<parameter-value:1>"
+          }
+        ],
+        "RollbackConfiguration": {},
+        "StackId": "arn:<partition>:cloudformation:<region>:111111111111:stack/<stack-name:1>/<resource:1>",
+        "StackName": "<stack-name:1>",
+        "StackStatus": "ROLLBACK_COMPLETE",
+        "Tags": []
+      }
+    }
   }
 }
@@ -2,6 +2,15 @@
   "tests/aws/services/cloudformation/resources/test_logs.py::test_cfn_handle_log_group_resource": {
     "last_validated_date": "2024-06-20T16:15:47+00:00"
   },
+  "tests/aws/services/cloudformation/resources/test_logs.py::test_handle_existing_log_group": {
+    "last_validated_date": "2025-10-06T16:24:57+00:00",
+    "durations_in_seconds": {
+      "setup": 0.81,
+      "call": 10.58,
+      "teardown": 0.22,
+      "total": 11.61
+    }
+  },
   "tests/aws/services/cloudformation/resources/test_logs.py::test_logstream": {
     "last_validated_date": "2022-07-29T11:22:53+00:00"
   }

@@ -1,8 +1,13 @@
+import copy
+import json
+
+import pytest
+from botocore.exceptions import ClientError
 from localstack_snapshot.snapshots.transformer import RegexTransformer
 from tests.aws.services.cloudformation.conftest import skip_if_legacy_engine
 
 from localstack.testing.pytest import markers
-from localstack.utils.strings import long_uid
+from localstack.utils.strings import long_uid, short_uid
 
 
 @skip_if_legacy_engine()
@@ -123,3 +128,64 @@ def test_update_parameter_default_value_with_dynamic_overrides(
         capture_update_process(
             snapshot, template_1, template_2, p1={"TopicName": name1}, p2={"TopicName": name2}
         )
+
+    @markers.aws.validated
+    def test_parameter_type_change(self, snapshot, capture_update_process):
+        snapshot.add_transformer(snapshot.transform.key_value("PhysicalResourceId"))
+
+        template1 = {
+            "Parameters": {
+                "Value": {
+                    "Type": "Number",
+                },
+            },
+            "Resources": {
+                "MyParameter": {
+                    "Type": "AWS::SSM::Parameter",
+                    "Properties": {
+                        "Type": "String",
+                        "Value": {"Ref": "Value"},
+                    },
+                },
+            },
+        }
+        template2 = copy.deepcopy(template1)
+        template2["Parameters"]["Value"]["Type"] = "String"
+
+        capture_update_process(
+            snapshot, template1, template2, p1={"Value": "123"}, p2={"Value": "456"}
+        )
+
+    @markers.aws.validated
+    def test_invalid_parameter_type(self, snapshot, aws_client):
+        template = {
+            "Parameters": {
+                "Value": {
+                    "Type": "Number",
+                },
+            },
+            "Resources": {
+                "MyParameter": {
+                    "Type": "AWS::SSM::Parameter",
+                    "Properties": {
+                        "Type": "String",
+                        "Value": short_uid(),
+                    },
+                },
+            },
+        }
+
+        stack_name = f"stack-{short_uid()}"
+        cs_name = f"cs-{short_uid()}"
+        with pytest.raises(ClientError) as exc_info:
+            aws_client.cloudformation.create_change_set(
+                ChangeSetName=cs_name,
+                StackName=stack_name,
+                ChangeSetType="CREATE",
+                TemplateBody=json.dumps(template),
+                Parameters=[
+                    {"ParameterKey": "Value", "ParameterValue": "not-a-number"},
+                ],
+            )
+
+        snapshot.match("error", exc_info.value.response)