fix(core): CHECKOUT-2450 Fix Reducer and Action type definition

Author: davidchin

src/action.ts

@@ -1,5 +1,5 @@
-export default interface Action<TPayload = any, TMeta = any> {
-    type: string;
+export default interface Action<TPayload = any, TMeta = any, TType extends string = string> {
+    type: TType;
     error?: boolean;
     meta?: TMeta;
     payload?: TPayload;

src/combine-reducers.spec.ts

@@ -7,7 +7,7 @@ describe('combineReducers()', () => {
         const state = { foo: 'FOO', bar: 'BAR' };
         const action = { type: 'ACTION' };
 
-        const reducer = combineReducers({
+        const reducer = combineReducers<{ foo: string, bar: string }>({
             foo: fooReducer,
             bar: barReducer,
         });

src/combine-reducers.ts

@@ -2,11 +2,11 @@ import { assign } from 'lodash';
 import Action from './action';
 import Reducer from './reducer';
 
-export default function combineReducers<TState, TAction extends Action>(
+export default function combineReducers<TState, TAction extends Action = Action>(
     reducers: ReducerMap<TState, TAction>
 ): Reducer<TState, TAction> {
     return (state, action) =>
-        Object.keys(reducers).reduce((result: TState, key) => {
+        Object.keys(reducers).reduce((result, key) => {
             const reducer = reducers[key as keyof TState];
             const currentState = state ? state[key as keyof TState] : undefined;
             const newState = reducer(currentState, action);
@@ -16,9 +16,9 @@ export default function combineReducers<TState, TAction extends Action>(
             }
 
             return assign({}, result, { [key]: newState });
-        }, state);
+        }, state || {} as TState);
 }
 
-export type ReducerMap<TState, TAction extends Action> = {
-    [Key in keyof TState]: Reducer<TState[Key] | undefined, TAction>;
+export type ReducerMap<TState, TAction extends Action = Action> = {
+    [Key in keyof TState]: Reducer<TState[Key], TAction>;
 };

src/compose-reducers.ts

@@ -2,7 +2,7 @@ import { curryRight, flowRight } from 'lodash';
 import Action from './action';
 import Reducer from './reducer';
 
-export default function composeReducers<TState, TAction extends Action>(
+export default function composeReducers<TState, TAction extends Action = Action>(
     ...reducers: Array<Reducer<Partial<TState>, TAction>>
 ): Reducer<TState, TAction> {
     return (state, action) =>

src/create-action.ts

@@ -1,11 +1,11 @@
 import { omitBy } from 'lodash';
 import Action from './action';
 
-export default function createAction<TPayload, TMeta>(
-    type: string,
+export default function createAction<TPayload, TMeta, TType extends string>(
+    type: TType,
     payload?: TPayload,
     meta?: TMeta
-): Action<TPayload, TMeta> {
+): Action<TPayload, TMeta, TType> {
     if (typeof type !== 'string' || type === '') {
         throw new Error('`type` must be a string');
     }

src/create-data-store.ts

@@ -3,8 +3,8 @@ import combineReducers, { ReducerMap } from './combine-reducers';
 import DataStore, { DataStoreOptions } from './data-store';
 import Reducer from './reducer';
 
-export default function createDataStore<TState, TAction extends Action, TTransformedState = TState>(
-    reducer: Reducer<Partial<TState>, TAction> | ReducerMap<Partial<TState>, TAction>,
+export default function createDataStore<TState, TAction extends Action = Action, TTransformedState = TState>(
+    reducer: Reducer<TState, TAction> | ReducerMap<TState, TAction>,
     initialState?: Partial<TState>,
     options?: Partial<DataStoreOptions<TState, TAction, TTransformedState>>
 ): DataStore<TState, TAction, TTransformedState> {

src/create-error-action.ts

@@ -1,11 +1,11 @@
 import Action from './action';
 import createAction from './create-action';
 
-export default function createErrorAction<TPayload, TMeta>(
-    type: string,
+export default function createErrorAction<TPayload, TMeta, TType extends string>(
+    type: TType,
     payload?: TPayload,
     meta?: TMeta
-): Action<TPayload, TMeta> {
+): Action<TPayload, TMeta, TType> {
     return {
         ...createAction(type, payload, meta),
         error: true,

src/data-store.ts

@@ -26,7 +26,7 @@ import 'rxjs/add/operator/mergeMap';
 import 'rxjs/add/operator/scan';
 
 export default class DataStore<TState, TAction extends Action = Action, TTransformedState = TState> implements ReadableDataStore<TTransformedState>, DispatchableDataStore<TTransformedState, TAction> {
-    private _reducer: Reducer<Partial<TState>, TAction>;
+    private _reducer: Reducer<TState, TAction>;
     private _options: DataStoreOptions<TState, TAction, TTransformedState>;
     private _notification$: Subject<TTransformedState>;
     private _dispatchers: { [key: string]: Dispatcher<TAction> };
@@ -35,7 +35,7 @@ export default class DataStore<TState, TAction extends Action = Action, TTransfo
     private _errors: { [key: string]: Subject<Error> };
 
     constructor(
-        reducer: Reducer<Partial<TState>, TAction>,
+        reducer: Reducer<TState, TAction>,
         initialState: Partial<TState> = {},
         options?: Partial<DataStoreOptions<TState, TAction, TTransformedState>>
     ) {
@@ -46,7 +46,7 @@ export default class DataStore<TState, TAction extends Action = Action, TTransfo
             actionTransformer: noopActionTransformer,
             ...options,
         };
-        this._state$ = new BehaviorSubject(this._options.stateTransformer(initialState));
+        this._state$ = new BehaviorSubject(this._options.stateTransformer(initialState as TState));
         this._notification$ = new Subject();
         this._dispatchers = {};
         this._dispatchQueue$ = new Subject();
@@ -57,7 +57,7 @@ export default class DataStore<TState, TAction extends Action = Action, TTransfo
             .filter((action) => !!action.type)
             .scan(
                 (states, action) => this._transformStates(states, action),
-                { state: initialState, transformedState: this._state$.getValue() }
+                { state: initialState as TState, transformedState: this._state$.getValue() }
             )
             .map(({ transformedState }) => transformedState)
             .distinctUntilChanged(isEqual)
@@ -110,9 +110,9 @@ export default class DataStore<TState, TAction extends Action = Action, TTransfo
     }
 
     private _transformStates(
-        states: StateTuple<Partial<TState>, TTransformedState>,
+        states: StateTuple<TState, TTransformedState>,
         action: TAction
-    ): StateTuple<Partial<TState>, TTransformedState> {
+    ): StateTuple<TState, TTransformedState> {
         const { state, transformedState } = states;
 
         try {
@@ -207,7 +207,7 @@ export default class DataStore<TState, TAction extends Action = Action, TTransfo
 export interface DataStoreOptions<TState, TAction, TTransformedState> {
     shouldWarnMutation: boolean;
     actionTransformer: (action: Observable<TAction>) => Observable<TAction>;
-    stateTransformer: (state: Partial<TState>) => TTransformedState;
+    stateTransformer: (state: TState) => TTransformedState;
 }
 
 interface StateTuple<TState, TTransformedState> {

src/dispatchable-data-store.ts

@@ -3,7 +3,7 @@ import Action from './action';
 import ThunkAction from './thunk-action';
 import ReadableDataStore from './readable-data-store';
 
-export default interface DispatchableDataStore<TTransformedState, TAction extends Action> extends ReadableDataStore<TTransformedState> {
+export default interface DispatchableDataStore<TTransformedState, TAction extends Action = Action> extends ReadableDataStore<TTransformedState> {
     dispatch: <TDispatchAction extends TAction>(
         action: DispatchableAction<TDispatchAction, TTransformedState>,
         options?: DispatchOptions

src/reducer.ts

@@ -1,5 +1,5 @@
 import Action from './action';
 
-type Reducer<TState, TAction extends Action> = (state: TState, action: TAction) => TState;
+type Reducer<TState, TAction extends Action = Action> = (state: TState | undefined, action: TAction) => TState;
 
 export default Reducer;