test(server-node): adding additional tests for initialization fix

this commit also changes the initialization callback funciton to `initializedCallback` from `basisRecieved` to be more clear on what the callback is for.

Author: joker23

packages/shared/sdk-server/__tests__/data_sources/createPayloadListenersFDv2.test.ts

@@ -104,23 +104,23 @@ const changesTransferNone = {
 
 describe('createPayloadListenerFDv2', () => {
   let dataSourceUpdates: LDTransactionalDataSourceUpdates;
-  let basisReceived: jest.Mock;
+  let initializedCallback: jest.Mock;
 
   beforeEach(() => {
     dataSourceUpdates = {
       init: jest.fn(),
       upsert: jest.fn(),
       applyChanges: jest.fn(),
     };
-    basisReceived = jest.fn();
+    initializedCallback = jest.fn();
   });
 
   afterEach(() => {
     jest.resetAllMocks();
   });
 
   test('data source updates called with basis true', async () => {
-    const listener = createPayloadListener(dataSourceUpdates, logger, basisReceived);
+    const listener = createPayloadListener(dataSourceUpdates, logger, initializedCallback);
     listener(fullTransferPayload);
 
     expect(logger.debug).toHaveBeenCalledWith(expect.stringMatching(/initializing/i));
@@ -141,7 +141,7 @@ describe('createPayloadListenerFDv2', () => {
   });
 
   test('data source updates called with basis false', async () => {
-    const listener = createPayloadListener(dataSourceUpdates, logger, basisReceived);
+    const listener = createPayloadListener(dataSourceUpdates, logger, initializedCallback);
     listener(changesTransferPayload);
 
     expect(logger.debug).toHaveBeenCalledWith(expect.stringMatching(/updating/i));
@@ -175,10 +175,72 @@ describe('createPayloadListenerFDv2', () => {
   });
 
   test('data source updates not called when basis is false and changes are empty', async () => {
-    const listener = createPayloadListener(dataSourceUpdates, logger, basisReceived);
+    const listener = createPayloadListener(dataSourceUpdates, logger, initializedCallback);
     listener(changesTransferNone);
 
     expect(logger.debug).toBeCalledWith(expect.stringMatching(/ignoring/i));
     expect(dataSourceUpdates.applyChanges).toHaveBeenCalledTimes(0);
   });
+
+  test('calls initializedCallback when state is non-empty (initial)', () => {
+    const listener = createPayloadListener(dataSourceUpdates, logger, initializedCallback);
+    let capturedCallback: (() => void) | undefined;
+
+    dataSourceUpdates.applyChanges = jest.fn((_basis, _data, callback) => {
+      capturedCallback = callback;
+    });
+
+    listener(fullTransferPayload);
+
+    expect(capturedCallback).toBeDefined();
+    expect(initializedCallback).not.toHaveBeenCalled();
+
+    // Simulate applyChanges calling the callback
+    capturedCallback?.();
+
+    expect(initializedCallback).toHaveBeenCalledTimes(1);
+  });
+
+  test('does not call initializedCallback when state is empty (file data initializer)', () => {
+    const fileDataPayload = {
+      initMetadata: {
+        environmentId: 'envId',
+      },
+      payload: {
+        id: 'payloadID',
+        version: 99,
+        state: '',
+        basis: true,
+        updates: [
+          {
+            kind: 'flag',
+            key: 'flagkey',
+            version: 1,
+            object: {
+              key: 'flagkey',
+              version: 1,
+            },
+          },
+        ],
+      },
+    };
+
+    const listener = createPayloadListener(dataSourceUpdates, logger, initializedCallback);
+    let capturedCallback: (() => void) | undefined;
+
+    dataSourceUpdates.applyChanges = jest.fn((_basis, _data, callback) => {
+      capturedCallback = callback;
+    });
+
+    listener(fileDataPayload);
+
+    expect(capturedCallback).toBeDefined();
+    expect(initializedCallback).not.toHaveBeenCalled();
+
+    // Simulate applyChanges calling the callback
+    capturedCallback?.();
+
+    // Should still not be called because state is empty
+    expect(initializedCallback).not.toHaveBeenCalled();
+  });
 });

packages/shared/sdk-server/src/data_sources/createPayloadListenerFDv2.ts

@@ -22,7 +22,7 @@ export const createPayloadListener =
   (
     dataSourceUpdates: LDTransactionalDataSourceUpdates,
     logger?: LDLogger,
-    basisReceived: VoidFunction = () => {},
+    initializedCallback: VoidFunction = () => {},
   ) =>
   (dataContainer: DataCallbackContainer) => {
     const { initMetadata, payload } = dataContainer;
@@ -70,10 +70,10 @@ export const createPayloadListener =
       converted,
       () => {
         if (payload.state !== '') {
-          // NOTE: this is a workaround for now. The only condition that we will consider a valid basis
+          // NOTE: The only condition that we will consider a valid basis
           // is when there is a valid selector. Currently, the only data source that does not have a
           // valid selector is the file data initializer, which will have a blank selector.
-          basisReceived();
+          initializedCallback();
         }
       },
       initMetadata,