set error to null instead of undefined to enable SSR with Next.js (getServerSideProps)

Author: gfortaine

src/core/buildSlice.ts

@@ -98,7 +98,7 @@ export function buildSlice({
             if (substate.requestId !== meta.requestId) return;
             substate.status = QueryStatus.fulfilled;
             substate.data = copyWithStructuralSharing(substate.data, payload.result);
-            substate.error = undefined;
+            substate.error = null;
             substate.fulfilledTimeStamp = payload.fulfilledTimeStamp;
           });
         })

test/buildHooks.test.tsx

@@ -423,7 +423,7 @@ describe('hooks tests', () => {
     expect(api.endpoints.getUser.select(USER_ID)(storeRef.store.getState())).toEqual({
       data: undefined,
       endpoint: 'getUser',
-      error: undefined,
+      error: null,
       fulfilledTimeStamp: expect.any(Number),
       internalQueryArgs: USER_ID,
       isError: false,
@@ -441,6 +441,7 @@ describe('hooks tests', () => {
     expect(api.endpoints.getUser.select(USER_ID)(storeRef.store.getState())).toEqual({
       data: undefined,
       endpoint: 'getUser',
+      error: null,
       fulfilledTimeStamp: expect.any(Number),
       internalQueryArgs: USER_ID,
       isError: false,
@@ -483,6 +484,7 @@ describe('hooks tests', () => {
     expect(api.endpoints.getUser.select(USER_ID)(storeRef.store.getState())).toEqual({
       data: undefined,
       endpoint: 'getUser',
+      error: null,
       fulfilledTimeStamp: expect.any(Number),
       internalQueryArgs: USER_ID,
       isError: false,
@@ -500,6 +502,7 @@ describe('hooks tests', () => {
     expect(api.endpoints.getUser.select(USER_ID)(storeRef.store.getState())).toEqual({
       data: undefined,
       endpoint: 'getUser',
+      error: null,
       fulfilledTimeStamp: expect.any(Number),
       internalQueryArgs: USER_ID,
       isError: false,
@@ -544,6 +547,7 @@ describe('hooks tests', () => {
     expect(api.endpoints.getUser.select(USER_ID)(storeRef.store.getState())).toEqual({
       data: undefined,
       endpoint: 'getUser',
+      error: null,
       fulfilledTimeStamp: expect.any(Number),
       internalQueryArgs: USER_ID,
       isError: false,
@@ -561,6 +565,7 @@ describe('hooks tests', () => {
     expect(api.endpoints.getUser.select(USER_ID)(storeRef.store.getState())).toEqual({
       data: undefined,
       endpoint: 'getUser',
+      error: null,
       fulfilledTimeStamp: expect.any(Number),
       internalQueryArgs: USER_ID,
       isError: false,

test/buildThunks.test.tsx

@@ -40,6 +40,7 @@ test('handles a non-async baseQuery without error', async () => {
     internalQueryArgs: {
       url: 'user/1',
     },
+    error: null,
     isError: false,
     isLoading: false,
     isSuccess: true,

test/errorHandling.test.tsx

@@ -148,7 +148,7 @@ describe('query error handling', () => {
         isError: false,
         isSuccess: true,
         data: { value: 'success' },
-        error: undefined,
+        error: null,
       })
     );
   });