refactor(toolkit-lib): drop the deep clone used to remove one metadata key

packages/@aws-cdk/toolkit-lib/lib/api/refactoring/digest.ts

@@ -143,7 +143,8 @@ function stripConstructPath(resource: any): any {
     return resource;
   }
 
-  const copy = JSON.parse(JSON.stringify(resource));
-  delete copy.Metadata['aws:cdk:path'];
-  return copy;
+  // A shallow copy is enough: the only thing being removed is one key of
+  // `Metadata`, and the caller only reads the result.
+  const { 'aws:cdk:path': _, ...metadata } = resource.Metadata;
+  return { ...resource, Metadata: metadata };
 }

packages/@aws-cdk/toolkit-lib/test/api/refactoring/refactoring.test.ts

@@ -392,6 +392,38 @@ describe(computeResourceDigests, () => {
     expect(result['Stack1.Q1']).toBe(result['Stack1.Q2']);
   });
 
+  test('other metadata still contributes to the digest, and the input is not modified', () => {
+    const makeTemplate = (assetPath: string) => ({
+      Resources: {
+        Q1: {
+          Type: 'AWS::SQS::Queue',
+          Properties: { Foo: 'Bar' },
+          Metadata: {
+            'aws:cdk:path': 'Stack/Q1/Resource',
+            'aws:asset:path': assetPath,
+          },
+        },
+      },
+    });
+
+    const template = makeTemplate('asset.1234');
+    const stacks = makeStacks([template]);
+    const digest = computeResourceDigests(stacks)['Stack1.Q1'];
+
+    // Metadata other than the construct path is part of the digest
+    const other = computeResourceDigests(makeStacks([makeTemplate('asset.5678')]))['Stack1.Q1'];
+    expect(digest).not.toBe(other);
+
+    // Computing the digest leaves the caller's template alone
+    expect(template.Resources.Q1.Metadata).toEqual({
+      'aws:cdk:path': 'Stack/Q1/Resource',
+      'aws:asset:path': 'asset.1234',
+    });
+
+    // ...and is stable across repeated calls
+    expect(computeResourceDigests(stacks)['Stack1.Q1']).toBe(digest);
+  });
+
   test('different physical IDs lead to different digests', () => {
     mockLoadResourceModel.mockReturnValue({
       primaryIdentifier: ['FooName'],