Merge pull request #3772 from Methuselah96/replace-reducer-rebase

resolves #3767
resolves #3482

Author: markerikson

src/createStore.ts

@@ -6,7 +6,6 @@ import {
   StoreEnhancer,
   Dispatch,
   Observer,
-  ExtendState,
   ListenerCallback
 } from './types/store'
 import { Action } from './types/actions'
@@ -43,7 +42,7 @@ import { kindOf } from './utils/kindOf'
 export function createStore<S, A extends Action, Ext = {}, StateExt = never>(
   reducer: Reducer<S, A>,
   enhancer?: StoreEnhancer<Ext, StateExt>
-): Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext
+): Store<S, A, StateExt> & Ext
 /**
  * @deprecated
  *
@@ -73,12 +72,12 @@ export function createStore<S, A extends Action, Ext = {}, StateExt = never>(
   reducer: Reducer<S, A>,
   preloadedState?: PreloadedState<S>,
   enhancer?: StoreEnhancer<Ext, StateExt>
-): Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext
+): Store<S, A, StateExt> & Ext
 export function createStore<S, A extends Action, Ext = {}, StateExt = never>(
   reducer: Reducer<S, A>,
   preloadedState?: PreloadedState<S> | StoreEnhancer<Ext, StateExt>,
   enhancer?: StoreEnhancer<Ext, StateExt>
-): Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext {
+): Store<S, A, StateExt> & Ext {
   if (typeof reducer !== 'function') {
     throw new Error(
       `Expected the root reducer to be a function. Instead, received: '${kindOf(
@@ -115,7 +114,7 @@ export function createStore<S, A extends Action, Ext = {}, StateExt = never>(
     return enhancer(createStore)(
       reducer,
       preloadedState as PreloadedState<S>
-    ) as Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext
+    ) as Store<S, A, StateExt> & Ext
   }
 
   let currentReducer = reducer
@@ -291,11 +290,8 @@ export function createStore<S, A extends Action, Ext = {}, StateExt = never>(
    * implement a hot reloading mechanism for Redux.
    *
    * @param nextReducer The reducer for the store to use instead.
-   * @returns The same store instance with a new reducer in place.
    */
-  function replaceReducer<NewState, NewActions extends A>(
-    nextReducer: Reducer<NewState, NewActions>
-  ): Store<ExtendState<NewState, StateExt>, NewActions, StateExt, Ext> & Ext {
+  function replaceReducer(nextReducer: Reducer<S, A>): void {
     if (typeof nextReducer !== 'function') {
       throw new Error(
         `Expected the nextReducer to be a function. Instead, received: '${kindOf(
@@ -304,22 +300,13 @@ export function createStore<S, A extends Action, Ext = {}, StateExt = never>(
       )
     }
 
-    // TODO: do this more elegantly
-    ;(currentReducer as unknown as Reducer<NewState, NewActions>) = nextReducer
+    currentReducer = nextReducer
 
     // This action has a similar effect to ActionTypes.INIT.
     // Any reducers that existed in both the new and old rootReducer
     // will receive the previous state. This effectively populates
     // the new state tree with any relevant data from the old one.
     dispatch({ type: ActionTypes.REPLACE } as A)
-    // change the type of the store by casting it to the new store
-    return store as unknown as Store<
-      ExtendState<NewState, StateExt>,
-      NewActions,
-      StateExt,
-      Ext
-    > &
-      Ext
   }
 
   /**
@@ -377,7 +364,7 @@ export function createStore<S, A extends Action, Ext = {}, StateExt = never>(
     getState,
     replaceReducer,
     [$$observable]: observable
-  } as unknown as Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext
+  } as unknown as Store<S, A, StateExt> & Ext
   return store
 }
 
@@ -419,7 +406,7 @@ export function legacy_createStore<
 >(
   reducer: Reducer<S, A>,
   enhancer?: StoreEnhancer<Ext, StateExt>
-): Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext
+): Store<S, A, StateExt> & Ext
 /**
  * Creates a Redux store that holds the state tree.
  *
@@ -459,7 +446,7 @@ export function legacy_createStore<
   reducer: Reducer<S, A>,
   preloadedState?: PreloadedState<S>,
   enhancer?: StoreEnhancer<Ext, StateExt>
-): Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext
+): Store<S, A, StateExt> & Ext
 export function legacy_createStore<
   S,
   A extends Action,
@@ -469,6 +456,6 @@ export function legacy_createStore<
   reducer: Reducer<S, A>,
   preloadedState?: PreloadedState<S> | StoreEnhancer<Ext, StateExt>,
   enhancer?: StoreEnhancer<Ext, StateExt>
-): Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext {
+): Store<S, A, StateExt> & Ext {
   return createStore(reducer, preloadedState as any, enhancer)
 }

src/types/store.ts

@@ -133,13 +133,11 @@ export type Observer<T> = {
  * @template S The type of state held by this store.
  * @template A the type of actions which may be dispatched by this store.
  * @template StateExt any extension to state from store enhancers
- * @template Ext any extensions to the store from store enhancers
  */
 export interface Store<
   S = any,
   A extends Action = AnyAction,
-  StateExt = never,
-  Ext = {}
+  StateExt = never
 > {
   /**
    * Dispatches an action. It is the only way to trigger a state change.
@@ -174,7 +172,7 @@ export interface Store<
    *
    * @returns The current state tree of your application.
    */
-  getState(): S
+  getState(): ExtendState<S, StateExt>
 
   /**
    * Adds a change listener. It will be called any time an action is
@@ -211,17 +209,15 @@ export interface Store<
    *
    * @param nextReducer The reducer for the store to use instead.
    */
-  replaceReducer<NewState, NewActions extends Action>(
-    nextReducer: Reducer<NewState, NewActions>
-  ): Store<ExtendState<NewState, StateExt>, NewActions, StateExt, Ext> & Ext
+  replaceReducer(nextReducer: Reducer<S, A>): void
 
   /**
    * Interoperability point for observable/reactive libraries.
    * @returns {observable} A minimal observable of state changes.
    * For more information, see the observable proposal:
    * https://github.com/tc39/proposal-observable
    */
-  [Symbol.observable](): Observable<S>
+  [Symbol.observable](): Observable<ExtendState<S, StateExt>>
 }
 
 /**
@@ -239,12 +235,12 @@ export interface StoreCreator {
   <S, A extends Action, Ext = {}, StateExt = never>(
     reducer: Reducer<S, A>,
     enhancer?: StoreEnhancer<Ext, StateExt>
-  ): Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext
+  ): Store<S, A, StateExt> & Ext
   <S, A extends Action, Ext = {}, StateExt = never>(
     reducer: Reducer<S, A>,
     preloadedState?: PreloadedState<S>,
     enhancer?: StoreEnhancer<Ext>
-  ): Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext
+  ): Store<S, A, StateExt> & Ext
 }
 
 /**
@@ -277,4 +273,4 @@ export type StoreEnhancerStoreCreator<Ext = {}, StateExt = never> = <
 >(
   reducer: Reducer<S, A>,
   preloadedState?: PreloadedState<S>
-) => Store<ExtendState<S, StateExt>, A, StateExt, Ext> & Ext
+) => Store<S, A, StateExt> & Ext

test/combineReducers.spec.ts

@@ -327,31 +327,35 @@ describe('Utils', () => {
       const ACTION = { type: 'ACTION' }
 
       it('should return an updated state when additional reducers are passed to combineReducers', function () {
-        const originalCompositeReducer = combineReducers({ foo })
+        type State = { foo: {}; bar?: {} }
+
+        const originalCompositeReducer = combineReducers<State>({ foo })
         const store = createStore(originalCompositeReducer)
 
         store.dispatch(ACTION)
 
         const initialState = store.getState()
 
-        store.replaceReducer(combineReducers({ foo, bar }))
+        store.replaceReducer(combineReducers<State>({ foo, bar }))
         store.dispatch(ACTION)
 
         const nextState = store.getState()
         expect(nextState).not.toBe(initialState)
       })
 
       it('should return an updated state when reducers passed to combineReducers are changed', function () {
+        type State = { foo?: {}; bar: {}; baz?: {} }
+
         const baz = (state = {}) => state
 
-        const originalCompositeReducer = combineReducers({ foo, bar })
+        const originalCompositeReducer = combineReducers<State>({ foo, bar })
         const store = createStore(originalCompositeReducer)
 
         store.dispatch(ACTION)
 
         const initialState = store.getState()
 
-        store.replaceReducer(combineReducers({ baz, bar }))
+        store.replaceReducer(combineReducers<State>({ baz, bar }))
         store.dispatch(ACTION)
 
         const nextState = store.getState()
@@ -374,7 +378,9 @@ describe('Utils', () => {
       })
 
       it('should return an updated state when one of more reducers passed to the combineReducers are removed', function () {
-        const originalCompositeReducer = combineReducers({ foo, bar })
+        const originalCompositeReducer = combineReducers<{ foo?: {}; bar: {} }>(
+          { foo, bar }
+        )
         const store = createStore(originalCompositeReducer)
 
         store.dispatch(ACTION)

test/createStore.spec.ts

@@ -824,7 +824,7 @@ describe('createStore', () => {
     console.error = jest.fn()
 
     const store = createStore(
-      combineReducers({
+      combineReducers<{ x?: number; y: { z: number; w?: number } }>({
         x: (s = 0, _) => s,
         y: combineReducers({
           z: (s = 0, _) => s,