fix(stepfunctions): repeated object references not allowed even if no…

…t a circular reference (#14628)

Popping the current node from `visited` array after finishing visiting it in `recurseObject` method. This allows another reference to the same object to happen on a different object path (currently being swallowed).

Created unit test before making any code changes to verify the failure scenario on the expected behavior before fixing it.

fixes #14596 

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-stepfunctions/lib/json-path.ts

@@ -83,11 +83,12 @@ interface FieldHandlers {
 
 export function recurseObject(obj: object | undefined, handlers: FieldHandlers, visited: object[] = []): object | undefined {
   if (obj === undefined) { return undefined; }
-  if (visited.includes(obj)) {
-    return {};
-  } else {
-    visited.push(obj);
-  }
+
+  // Avoiding infinite recursion
+  if (visited.includes(obj)) { return {}; }
+
+  // Marking current object as visited for the current recursion path
+  visited.push(obj);
 
   const ret: any = {};
   for (const [key, value] of Object.entries(obj)) {
@@ -106,6 +107,10 @@ export function recurseObject(obj: object | undefined, handlers: FieldHandlers,
     }
   }
 
+  // Removing from visited after leaving the current recursion path
+  // Allowing it to be visited again if it's not causing a recursion (circular reference)
+  visited.pop();
+
   return ret;
 }
 

packages/@aws-cdk/aws-stepfunctions/test/fields.test.ts

@@ -152,4 +152,26 @@ describe('Fields', () => {
     expect(FieldUtils.findReferencedPaths(paths))
       .toStrictEqual(['$.listField', '$.numField', '$.stringField']);
   });
+
+  test('repeated object references at different tree paths should not be considered as recursions', () => {
+    const repeatedObject = {
+      field: JsonPath.stringAt('$.stringField'),
+      numField: JsonPath.numberAt('$.numField'),
+    };
+    expect(FieldUtils.renderObject(
+      {
+        reference1: repeatedObject,
+        reference2: repeatedObject,
+      },
+    )).toStrictEqual({
+      reference1: {
+        'field.$': '$.stringField',
+        'numField.$': '$.numField',
+      },
+      reference2: {
+        'field.$': '$.stringField',
+        'numField.$': '$.numField',
+      },
+    });
+  });
 });