Mapped type for combineReducers in index.d.ts

index.d.ts

@@ -43,13 +43,13 @@ export interface Action {
  *
  * @template S State object type.
  */
-export type Reducer<S> = <A extends Action>(state: S, action: A) => S;
+export type Reducer<S> = <A extends Action>(state: S | undefined, action: A) => S;
 
 /**
  * Object whose values correspond to different reducer functions.
  */
-export interface ReducersMapObject {
-  [key: string]: Reducer<any>;
+export type ReducersMapObject<S> = {
+  [K in keyof S]: Reducer<S[K]>;
 }
 
 /**
@@ -70,7 +70,7 @@ export interface ReducersMapObject {
  * @returns A reducer function that invokes every reducer inside the passed
  *   object, and builds a state object with the same shape.
  */
-export function combineReducers<S>(reducers: ReducersMapObject): Reducer<S>;
+export function combineReducers<S>(reducers: ReducersMapObject<S>): Reducer<S>;
 
 
 /* store */
@@ -93,7 +93,9 @@ export function combineReducers<S>(reducers: ReducersMapObject): Reducer<S>;
  * transform, delay, ignore, or otherwise interpret actions or async actions
  * before passing them to the next middleware.
  */
-export type Dispatch = (action: any) => any;
+export interface Dispatch<S> {
+    <A extends Action>(action: A): A;
+}
 
 /**
  * Function to remove listener added by `Store.subscribe()`.
@@ -136,7 +138,7 @@ export interface Store<S> {
    * Note that, if you use a custom middleware, it may wrap `dispatch()` to
    * return something else (for example, a Promise you can await).
    */
-  dispatch: Dispatch;
+  dispatch: Dispatch<S>;
 
   /**
    * Reads the state tree managed by the store.
@@ -251,7 +253,7 @@ export const createStore: StoreCreator;
 /* middleware */
 
 export interface MiddlewareAPI<S> {
-  dispatch: Dispatch;
+  dispatch: Dispatch<S>;
   getState(): S;
 }
 
@@ -265,7 +267,7 @@ export interface MiddlewareAPI<S> {
  * asynchronous API call into a series of synchronous actions.
  */
 export interface Middleware {
-  <S>(api: MiddlewareAPI<S>): (next: Dispatch) => (action: any) => any;
+  <S>(api: MiddlewareAPI<S>): (next: Dispatch<S>) => Dispatch<S>;
 }
 
 /**
@@ -337,19 +339,19 @@ export interface ActionCreatorsMapObject {
  *   creator wrapped into the `dispatch` call. If you passed a function as
  *   `actionCreator`, the return value will also be a single function.
  */
-export function bindActionCreators<A extends ActionCreator<any>>(actionCreator: A, dispatch: Dispatch): A;
+export function bindActionCreators<A extends ActionCreator<any>>(actionCreator: A, dispatch: Dispatch<any>): A;
 
 export function bindActionCreators<
   A extends ActionCreator<any>,
   B extends ActionCreator<any>
-  >(actionCreator: A, dispatch: Dispatch): B;
+  >(actionCreator: A, dispatch: Dispatch<any>): B;
 
-export function bindActionCreators<M extends ActionCreatorsMapObject>(actionCreators: M, dispatch: Dispatch): M;
+export function bindActionCreators<M extends ActionCreatorsMapObject>(actionCreators: M, dispatch: Dispatch<any>): M;
 
 export function bindActionCreators<
   M extends ActionCreatorsMapObject,
   N extends ActionCreatorsMapObject
-  >(actionCreators: M, dispatch: Dispatch): N;
+  >(actionCreators: M, dispatch: Dispatch<any>): N;
 
 
 /* compose */

package.json

@@ -100,8 +100,8 @@
     "isparta": "^4.0.0",
     "mocha": "^2.2.5",
     "rimraf": "^2.3.4",
-    "typescript": "^1.8.0",
-    "typescript-definition-tester": "0.0.4",
+    "typescript": "^2.1.0",
+    "typescript-definition-tester": "0.0.5",
     "webpack": "^1.9.6"
   },
   "npmName": "redux",

test/typescript.spec.js

@@ -8,6 +8,9 @@ describe('TypeScript definitions', function () {
     tt.compileDirectory(
       __dirname + '/typescript',
       fileName => fileName.match(/\.ts$/),
+      {
+        strictNullChecks: true
+      },
       () => done()
     )
   })

test/typescript/actionCreators.ts

@@ -1,7 +1,7 @@
 import {
   ActionCreator, Action, Dispatch,
   bindActionCreators, ActionCreatorsMapObject
-} from "../../index.d.ts";
+} from "../../";
 
 
 interface AddTodoAction extends Action {
@@ -15,15 +15,15 @@ const addTodo: ActionCreator<AddTodoAction> = (text: string) => ({
 
 const addTodoAction: AddTodoAction = addTodo('test');
 
-type AddTodoThunk = (dispatch: Dispatch) => AddTodoAction;
+type AddTodoThunk = (dispatch: Dispatch<any>) => AddTodoAction;
 
 const addTodoViaThunk: ActionCreator<AddTodoThunk> = (text: string) =>
-  (dispatch: Dispatch) => ({
+  (dispatch: Dispatch<any>) => ({
     type: 'ADD_TODO',
     text
   })
 
-declare const dispatch: Dispatch;
+declare const dispatch: Dispatch<any>;
 
 const boundAddTodo = bindActionCreators(addTodo, dispatch);
 

test/typescript/actions.ts

@@ -1,4 +1,4 @@
-import {Action as ReduxAction} from "../../index.d.ts";
+import {Action as ReduxAction} from "../../";
 
 
 namespace FSA {

test/typescript/compose.ts

@@ -1,4 +1,4 @@
-import {compose} from "../../index.d.ts";
+import {compose} from "../../";
 
 // copied from DefinitelyTyped/compose-function
 

test/typescript/dispatch.ts

@@ -1,12 +1,15 @@
-import {Dispatch, Action} from "../../index.d.ts";
+import {Dispatch, Action} from "../../";
 
 
-declare const dispatch: Dispatch;
+declare const dispatch: Dispatch<any>;
 
 
 const dispatchResult: Action = dispatch({type: 'TYPE'});
 
-
-type Thunk<O> = () => O;
+declare module "../../" {
+    export interface Dispatch<S> {
+        <R>(asyncAction: (dispatch: Dispatch<S>, getState: () => S) => R): R;
+    }
+}
 
 const dispatchThunkResult: number = dispatch(() => 42);

test/typescript/middleware.ts

@@ -1,23 +1,28 @@
 import {
   Middleware, MiddlewareAPI,
   applyMiddleware, createStore, Dispatch, Reducer, Action
-} from "../../index.d.ts";
+} from "../../";
 
+declare module "../../" {
+    export interface Dispatch<S> {
+        <R>(asyncAction: (dispatch: Dispatch<S>, getState: () => S) => R): R;
+    }
+}
 
-type Thunk<S, O> = (dispatch: Dispatch, getState?: () => S) => O;
+type Thunk<S, O> = (dispatch: Dispatch<S>, getState?: () => S) => O;
 
 const thunkMiddleware: Middleware =
   <S>({dispatch, getState}: MiddlewareAPI<S>) =>
-    (next: Dispatch) =>
-      <A, B>(action: A | Thunk<S, B>): B =>
+    (next: Dispatch<S>) =>
+      <A extends Action, B>(action: A | Thunk<S, B>): B|Action =>
         typeof action === 'function' ?
           (<Thunk<S, B>>action)(dispatch, getState) :
-          <B>next(<A>action)
+          next(<A>action)
 
 
 const loggerMiddleware: Middleware =
   <S>({getState}: MiddlewareAPI<S>) =>
-    (next: Dispatch) =>
+    (next: Dispatch<S>) =>
       (action: any): any => {
         console.log('will dispatch', action)
 
@@ -47,7 +52,7 @@ const storeWithThunkMiddleware = createStore(
 );
 
 storeWithThunkMiddleware.dispatch(
-  (dispatch: Dispatch, getState: () => State) => {
+  (dispatch: Dispatch<State>, getState: () => State) => {
     const todos: string[] = getState().todos;
     dispatch({type: 'ADD_TODO'})
   }

test/typescript/reducers.ts

@@ -1,7 +1,7 @@
 import {
   Reducer, Action, combineReducers,
   ReducersMapObject
-} from "../../index.d.ts";
+} from "../../";
 
 
 type TodosState = string[];
@@ -47,8 +47,7 @@ type RootState = {
   counter: CounterState;
 }
 
-
-const rootReducer: Reducer<RootState> = combineReducers<RootState>({
+const rootReducer: Reducer<RootState> = combineReducers({
   todos: todosReducer,
   counter: counterReducer,
 })

test/typescript/store.ts

@@ -1,7 +1,7 @@
 import {
   Store, createStore, Reducer, Action, StoreEnhancer,
   StoreCreator, Unsubscribe
-} from "../../index.d.ts";
+} from "../../";
 
 
 type State = {