add cfn transformation function with key skip (#12976)

baermat · web-flow · commit 18c73b01bd3c · 2025-08-12T10:49:32.000+02:00
diff --git a/localstack-core/localstack/services/cloudformation/provider_utils.py b/localstack-core/localstack/services/cloudformation/provider_utils.py
@@ -73,9 +73,12 @@ def recurse_properties(properties: dict, fn: Callable) -> dict:
     return _recurse_properties(deepcopy(properties), fn)
 
 
-def keys_pascalcase_to_lower_camelcase(model: dict) -> dict:
+def keys_pascalcase_to_lower_camelcase(model: dict, skip_keys: set = None) -> dict:
     """Recursively change any dicts keys to lower camelcase"""
 
+    if skip_keys:
+        return _pascal_to_camel_keys_preserve_values(model, skip_keys)
+
     def _keys_pascalcase_to_lower_camelcase(obj):
         if isinstance(obj, dict):
             return {convert_pascalcase_to_lower_camelcase(k): v for k, v in obj.items()}
@@ -85,6 +88,33 @@ def _keys_pascalcase_to_lower_camelcase(obj):
     return _recurse_properties(model, _keys_pascalcase_to_lower_camelcase)
 
 
+def _pascal_to_camel_keys_preserve_values(model: dict, skip_keys: set = None) -> dict:
+    """
+    Variant of keys_pascalcase_to_lower_camelcase
+    All VALUES of provided keys are skipped and not transformed to lower camelcase.
+    The keys themselves will be transformed.
+    The function simply stops recursion if a key matches, so make sure no lower level values are ignored.
+    """
+    skip_keys = skip_keys or set()
+
+    def _transform(obj):
+        if isinstance(obj, dict):
+            new_dict = {}
+            for k, v in obj.items():
+                new_key = convert_pascalcase_to_lower_camelcase(k)
+                if k in skip_keys:
+                    new_dict[new_key] = v
+                else:
+                    new_dict[new_key] = _transform(v)
+            return new_dict
+        elif isinstance(obj, list):
+            return [_transform(i) for i in obj]
+        else:
+            return obj
+
+    return _transform(model)
+
+
 def keys_lower_camelcase_to_pascalcase(model: dict) -> dict:
     """Recursively change any dicts keys to PascalCase"""
 
diff --git a/tests/unit/services/cloudformation/test_provider_utils.py b/tests/unit/services/cloudformation/test_provider_utils.py
@@ -135,3 +135,68 @@ def test_lower_camelcase_to_pascalcase(self):
                 }
             ],
         }
+
+    def test_lower_camelcase_to_pascalcase_skip_keys(self):
+        original_dict = {
+            "Stages": [
+                {
+                    "Actions": [
+                        {
+                            "Actiontypeid": {
+                                "Category": "Source",
+                                "Owner": "AWS",
+                                "Provider": "S3",
+                                "Version": "1",
+                            },
+                            "Configuration": {
+                                "S3bucket": "localstack-codepipeline-source-86a13a88",
+                                "S3objectkey": "source-key",
+                                "Subconfig": {"Subconfig1": "Foo", "Subconfig2": "bar"},
+                            },
+                            "Inputartifacts": [],
+                            "Name": "S3Source",
+                            "Namespace": "S3SourceVariables",
+                            "Outputartifacts": [{"Name": "Artifact_Source_S3Source"}],
+                            "Rolearn": "arn:aws:iam::096845016391:role/EcrPipelineStack-MyPipelineSourceS3SourceCodePipeli-YOoRQUZQe6WU",
+                            "Runorder": 1,
+                        }
+                    ],
+                    "Name": "Source",
+                }
+            ]
+        }
+        target_dict = {
+            "stages": [
+                {
+                    "actions": [
+                        {
+                            "actiontypeid": {
+                                "category": "Source",
+                                "owner": "AWS",
+                                "provider": "S3",
+                                "version": "1",
+                            },
+                            # The excluded key itself is transformed
+                            # Its values are not
+                            # Recursion stops, items at lower levels are not transformed as well
+                            "configuration": {
+                                "S3bucket": "localstack-codepipeline-source-86a13a88",
+                                "S3objectkey": "source-key",
+                                "Subconfig": {"Subconfig1": "Foo", "Subconfig2": "bar"},
+                            },
+                            "inputartifacts": [],
+                            "name": "S3Source",
+                            "namespace": "S3SourceVariables",
+                            "outputartifacts": [{"name": "Artifact_Source_S3Source"}],
+                            "rolearn": "arn:aws:iam::096845016391:role/EcrPipelineStack-MyPipelineSourceS3SourceCodePipeli-YOoRQUZQe6WU",
+                            "runorder": 1,
+                        }
+                    ],
+                    "name": "Source",
+                }
+            ]
+        }
+        converted_dict = utils.keys_pascalcase_to_lower_camelcase(
+            original_dict, skip_keys={"Configuration"}
+        )
+        assert converted_dict == target_dict
