feat(idempotency): return existing record in IdempotencyValidationError

packages/idempotency/src/errors.ts

@@ -30,7 +30,14 @@ class IdempotencyInvalidStatusError extends Error {}
 /**
  * Payload does not match stored idempotency record
  */
-class IdempotencyValidationError extends Error {}
+class IdempotencyValidationError extends Error {
+  public existingRecord?: IdempotencyRecord;
+
+  public constructor(message?: string, existingRecord?: IdempotencyRecord) {
+    super(message);
+    this.existingRecord = existingRecord;
+  }
+}
 
 /**
  * State is inconsistent across multiple requests to persistence store

packages/idempotency/src/persistence/BasePersistenceLayer.ts

@@ -319,7 +319,8 @@ abstract class BasePersistenceLayer implements BasePersistenceLayerInterface {
       const hashedPayload: string = this.getHashedPayload(data);
       if (hashedPayload !== record.payloadHash) {
         throw new IdempotencyValidationError(
-          'Payload does not match stored record for this event key'
+          'Payload does not match stored record for this event key',
+          record
         );
       }
     }

packages/idempotency/tests/unit/persistence/BasePersistenceLayer.test.ts

@@ -243,18 +243,20 @@ describe('Class: BasePersistenceLayer', () => {
           payloadValidationJmesPath: 'foo',
         }),
       });
-      jest.spyOn(persistenceLayer, '_getRecord').mockReturnValue(
-        new IdempotencyRecord({
-          idempotencyKey: 'my-lambda-function#mocked-hash',
-          status: IdempotencyRecordStatus.INPROGRESS,
-          payloadHash: 'different-hash',
-        })
-      );
+      const existingRecord = new IdempotencyRecord({
+        idempotencyKey: 'my-lambda-function#mocked-hash',
+        status: IdempotencyRecordStatus.INPROGRESS,
+        payloadHash: 'different-hash',
+      });
+      jest
+        .spyOn(persistenceLayer, '_getRecord')
+        .mockReturnValue(existingRecord);
 
       // Act & Assess
       await expect(persistenceLayer.getRecord({ foo: 'bar' })).rejects.toThrow(
         new IdempotencyValidationError(
-          'Payload does not match stored record for this event key'
+          'Payload does not match stored record for this event key',
+          existingRecord
         )
       );
     });