Extract engine_parameter_value

simonrw · simonrw · commit 10bb97b9940d · 2025-08-08T23:08:27.000+01:00
diff --git a/localstack-core/localstack/services/cloudformation/engine/v2/change_set_model.py b/localstack-core/localstack/services/cloudformation/engine/v2/change_set_model.py
@@ -13,7 +13,10 @@
 from localstack.utils.strings import camel_to_snake_case
 
 if TYPE_CHECKING:
-    from localstack.services.cloudformation.v2.entities import EngineParameter
+    from localstack.services.cloudformation.v2.entities import (
+        EngineParameter,
+        engine_parameter_value,
+    )
 
 T = TypeVar("T")
 
@@ -1019,18 +1022,14 @@ def _visit_dynamic_parameter(self, parameter_name: str) -> ChangeSetEntity:
 
         before_parameter = Nothing
         if not is_nothing(before_parameter_dct):
-            before_parameter = (
-                before_parameter_dct.get("resolved_value")
-                or before_parameter_dct["given_value"]
-                or before_parameter_dct.get("default_value")
+            before_parameter = before_parameter_dct.get("resolved_value") or engine_parameter_value(
+                before_parameter_dct
             )
 
         after_parameter = Nothing
         if not is_nothing(after_parameter_dct):
-            after_parameter = (
-                after_parameter_dct.get("resolved_value")
-                or after_parameter_dct["given_value"]
-                or after_parameter_dct.get("default_value")
+            after_parameter = after_parameter_dct.get("resolved_value") or engine_parameter_value(
+                after_parameter_dct
             )
 
         parameter = self._visit_value(
diff --git a/localstack-core/localstack/services/cloudformation/v2/entities.py b/localstack-core/localstack/services/cloudformation/v2/entities.py
@@ -45,6 +45,14 @@ class EngineParameter(TypedDict):
     default_value: NotRequired[str | None]
 
 
+def engine_parameter_value(parameter: EngineParameter) -> str:
+    value = parameter.get("given_value") or parameter.get("default_value")
+    if value is None:
+        raise RuntimeError("Parameter value is None")
+
+    return value
+
+
 class ResolvedResource(TypedDict):
     LogicalResourceId: str
     Type: str
