fix: copy resource metadata before normalizing the information in it

samcli/lib/samlib/resource_metadata_normalizer.py

@@ -5,6 +5,7 @@
 import json
 import logging
 import re
+from copy import deepcopy
 from pathlib import Path
 from typing import Dict
 
@@ -61,10 +62,8 @@ def normalize(template_dict, normalize_parameters=False):
         resources = template_dict.get(RESOURCES_KEY, {})
 
         for logical_id, resource in resources.items():
-            resource_metadata = resource.get(METADATA_KEY)
-            if resource_metadata is None:
-                resource_metadata = {}
-                resource[METADATA_KEY] = resource_metadata
+            # copy metadata to another variable, change its values and assign it back in the end
+            resource_metadata = deepcopy(resource.get(METADATA_KEY)) or {}
 
             is_normalized = resource_metadata.get(SAM_IS_NORMALIZED, False)
             if not is_normalized:
@@ -97,6 +96,7 @@ def normalize(template_dict, normalize_parameters=False):
                 resource_metadata,
                 {SAM_RESOURCE_ID_KEY: ResourceMetadataNormalizer.get_resource_id(resource, logical_id)},
             )
+            resource[METADATA_KEY] = resource_metadata
 
         # This is a work around to allow the customer to use sam deploy or package commands without the need to provide
         # values for the CDK auto generated asset parameters. The suggested solution is to let CDK add some metadata to

tests/unit/lib/samlib/test_resource_metadata_normalizer.py

@@ -3,6 +3,7 @@
 from unittest import TestCase
 
 from samcli.lib.samlib.resource_metadata_normalizer import ResourceMetadataNormalizer
+from samcli.yamlhelper import yaml_parse
 
 
 class TestResourceMetadataNormalizer(TestCase):
@@ -456,6 +457,50 @@ def test_skip_normalizing_already_normalized_resource(self):
         self.assertEqual("new path", template_data["Resources"]["Function1"]["Properties"]["Code"])
         self.assertEqual("Function1", template_data["Resources"]["Function1"]["Metadata"]["SamResourceId"])
 
+    def test_with_referenced_metadata(self):
+        input_template = """
+        Resources:
+          FirstFunction:
+            Type: AWS::Serverless::Function
+            Metadata: &GoFunctionMetadata
+              BuildMethod: go1.x
+              BuildProperties:
+                TrimGoPath: true
+            Properties:
+              CodeUri: dummy
+              Handler: bootstrap
+              Runtime: provided.al2
+          SecondFunction:
+            Type: AWS::Serverless::Function
+            Metadata: *GoFunctionMetadata
+            Properties:
+              CodeUri: dummy
+              Handler: bootstrap
+              Runtime: provided.al2
+          ThirdFunction:
+            Type: AWS::Serverless::Function
+            Metadata: *GoFunctionMetadata
+            Properties:
+              CodeUri: dummy
+              Handler: bootstrap
+              Runtime: provided.al2
+        """
+        template_dict = yaml_parse(input_template)
+        ResourceMetadataNormalizer.normalize(template_dict)
+
+        self.assertEqual(
+            template_dict.get("Resources", {}).get("FirstFunction", {}).get("Metadata", {}).get("SamResourceId"),
+            "FirstFunction",
+        )
+        self.assertEqual(
+            template_dict.get("Resources", {}).get("SecondFunction", {}).get("Metadata", {}).get("SamResourceId"),
+            "SecondFunction",
+        )
+        self.assertEqual(
+            template_dict.get("Resources", {}).get("ThirdFunction", {}).get("Metadata", {}).get("SamResourceId"),
+            "ThirdFunction",
+        )
+
 
 class TestResourceMetadataNormalizerGetResourceId(TestCase):
     @parameterized.expand(