Preserve nullable store state type by avoiding intersection with {}

packages/toolkit/package.json

@@ -112,7 +112,7 @@
   ],
   "dependencies": {
     "immer": "^10.0.3",
-    "redux": "^5.0.0",
+    "redux": "^5.0.1",
     "redux-thunk": "^3.1.0",
     "reselect": "^5.0.1"
   },

packages/toolkit/src/configureStore.ts

@@ -26,6 +26,7 @@ import type {
   ExtractDispatchExtensions,
   ExtractStoreExtensions,
   ExtractStateExtensions,
+  UnknownIfNonSpecific,
 } from './tsHelpers'
 import type { Tuple } from './utils'
 import type { GetDefaultEnhancers } from './getDefaultEnhancers'
@@ -103,7 +104,8 @@ export type EnhancedStore<
   S = any,
   A extends Action = UnknownAction,
   E extends Enhancers = Enhancers
-> = ExtractStoreExtensions<E> & Store<S & ExtractStateExtensions<E>, A>
+> = ExtractStoreExtensions<E> &
+  Store<S, A, UnknownIfNonSpecific<ExtractStateExtensions<E>>>
 
 /**
  * A friendly abstraction over the standard Redux `createStore()` function.

packages/toolkit/src/tests/configureStore.typetest.ts

@@ -13,7 +13,7 @@ import type { PayloadAction, ConfigureStoreOptions } from '@reduxjs/toolkit'
 import { configureStore, createSlice, Tuple } from '@reduxjs/toolkit'
 import type { ThunkMiddleware, ThunkAction, ThunkDispatch } from 'redux-thunk'
 import { thunk } from 'redux-thunk'
-import { expectNotAny, expectType } from './helpers'
+import { expectExactType, expectNotAny, expectType } from './helpers'
 
 const _anyMiddleware: any = () => () => () => {}
 
@@ -138,6 +138,17 @@ const _anyMiddleware: any = () => () => () => {}
   })
 }
 
+/**
+ * Test: nullable state is preserved
+ */
+
+{
+  const store = configureStore({
+    reducer: (): string | null => null,
+  })
+  expectExactType<string | null>(null)(store.getState())
+}
+
 /*
  * Test: configureStore() accepts store Tuple, but not plain array
  */

packages/toolkit/src/tsHelpers.ts

@@ -205,3 +205,5 @@ export type Id<T> = { [K in keyof T]: T[K] } & {}
 export type Tail<T extends any[]> = T extends [any, ...infer Tail]
   ? Tail
   : never
+
+export type UnknownIfNonSpecific<T> = {} extends T ? unknown : T

yarn.lock

@@ -7075,7 +7075,7 @@ __metadata:
     node-fetch: ^2.6.1
     prettier: ^2.2.1
     query-string: ^7.0.1
-    redux: ^5.0.0
+    redux: ^5.0.1
     redux-thunk: ^3.1.0
     reselect: ^5.0.1
     rimraf: ^3.0.2
@@ -25152,10 +25152,10 @@ fsevents@^1.2.7:
   languageName: node
   linkType: hard
 
-"redux@npm:^5.0.0":
-  version: 5.0.0
-  resolution: "redux@npm:5.0.0"
-  checksum: be49160d4bd01e10108c425ade999f1b456204895c4bdd0c7825ab09efffded51955c5c242847406a7b3f273e9011a9c102848c512a099a75617b97b13d2cca8
+"redux@npm:^5.0.1":
+  version: 5.0.1
+  resolution: "redux@npm:5.0.1"
+  checksum: e74affa9009dd5d994878b9a1ce30d6569d986117175056edb003de2651c05b10fe7819d6fa94aea1a94de9a82f252f986547f007a2fbeb35c317a2e5f5ecf2c
   languageName: node
   linkType: hard