fix: improve typings for deps/inject and action payload

Author: Temzasse

example/typed/src/components/order/order.model.ts

@@ -43,7 +43,7 @@ const model = createModel<State, Actions, Deps>({
   },
   actions: ({ initialState }) => ({
     // Basic actions
-    fooAction: (state, action: { payload: number }) => ({
+    fooAction: (state, action) => ({
       ...state,
       foo: action.payload,
     }),

example/typed/typings/reducktion/index.d.ts

@@ -1,67 +1,77 @@
 declare module 'reducktion' {
+  // Helper
+  type ArgumentType<F extends Function> = F extends (arg: infer A) => any
+    ? A
+    : never;
+
+  // TODO: do we need this?
   interface RootState<StatePart> {
     [statePart: string]: StatePart;
   }
-  
+
   type Selector<State> = (state: RootState<State>, ...args: any[]) => any;
-  
+
   // Provide action keys for auto-complete but allow custom types
   // that are eg. auto-generated by fetchable action
   type ActionTypes<Actions> = { [K in keyof Actions]: string } & {
     [x: string]: string;
   };
-  
-  interface ActionCreator<Payload = any> {
+
+  interface ActionCreator<Payload> {
     type: string;
     payload: Payload;
     [x: string]: any; // Allow additional meta fields
   }
-  
+
   type ActionFunc<Payload = any> = (
     payload?: Payload
   ) => ActionCreator<Payload>;
-  
+
   type Thunk<Deps> = (
     arg: any,
     deps: Deps
   ) => (dispatch: any, getState: () => any, ...args: any[]) => Promise<void>;
-  
+
   type Reducer<State, Payload = any> = (
     state: State,
     action: ActionCreator<Payload>
   ) => State;
-  
+
   interface FetchableReducers<State> {
     loading: Reducer<State>;
     success: Reducer<State>;
     failure: Reducer<State>;
   }
-  
+
   interface Fetchable {
-    value: <T>(val: T) => FetchableValue<T>,
+    value: <T>(val: T) => FetchableValue<T>;
     action: <State, K extends keyof State>(
       // Only allow state fields for fetchable values
       stateField: FetchableValue extends State[K] ? K : never,
       customReducers?: Partial<FetchableReducers<State>>
-    ) => FetchableReducers<State>,
+    ) => FetchableReducers<State>;
   }
-  
+
   interface Dependencies {
     [depName: string]: Model<any, any>;
   }
-  
+
   // TODO:
   // Figure out how to show proper error
   // if given action is not in keyof Actions
   interface ModelDefinition<State, Actions, Deps> {
     name: string;
-    inject?: string[];
+    inject?: [keyof Deps];
     state: State;
     actions: (
       { initialState }: { initialState: State }
     ) => {
       // Only include those keys that are present in the action's interface
-      [K in keyof Actions]: Reducer<State> | FetchableReducers<State>
+      [K in keyof Actions]: Actions[K] extends FetchableAction<any>
+        ? FetchableReducers<State>
+        : Actions[K] extends Function
+        ? Reducer<State, ArgumentType<Actions[K]>>
+        : never
     };
     reactions?: (
       { initialState, deps }: { initialState: State; deps: Deps }
@@ -81,7 +91,7 @@ declare module 'reducktion' {
       [thunkName: string]: Thunk<Deps>;
     };
   }
-  
+
   interface Model<State, Actions> {
     name: string;
     initialState: State;
@@ -95,34 +105,34 @@ declare module 'reducktion' {
     getSagas: () => [];
     getReducer: () => Reducer<any>;
   }
-  
+
   // EXPORTS ********************************************************************
-  
+
   export enum FetchableStatus {
     INITIAL,
     LOADING,
     SUCCESS,
     FAILURE,
   }
-  
+
   export interface FetchableValue<Data = any> {
     data: Data;
     error: any;
     status: FetchableStatus;
   }
-  
+
   export interface FetchableAction<SuccessData> extends ActionFunc {
     init: ActionFunc;
     fail: ActionFunc;
     success: ActionFunc<SuccessData>;
   }
-  
+
   export const fetchable: Fetchable;
-  
+
   export function createModel<State, Actions, Deps = Dependencies>(
     df: ModelDefinition<State, Actions, Deps>
   ): Model<State, Actions>;
-  
+
   export function initModels(
     models: Model<any, any>[]
   ): {
@@ -132,5 +142,5 @@ declare module 'reducktion' {
     allSagas: any[];
   } & {
     [modelName: string]: Model<any, any>;
-  };  
+  };
 }

src/reducktion.d.ts

@@ -1,3 +1,9 @@
+// Helper
+type ArgumentType<F extends Function> = F extends (arg: infer A) => any
+  ? A
+  : never;
+
+// TODO: do we need this?
 interface RootState<StatePart> {
   [statePart: string]: StatePart;
 }
@@ -10,7 +16,7 @@ type ActionTypes<Actions> = { [K in keyof Actions]: string } & {
   [x: string]: string;
 };
 
-interface ActionCreator<Payload = any> {
+interface ActionCreator<Payload> {
   type: string;
   payload: Payload;
   [x: string]: any; // Allow additional meta fields
@@ -37,12 +43,12 @@ interface FetchableReducers<State> {
 }
 
 interface Fetchable {
-  value: <T>(val: T) => FetchableValue<T>,
+  value: <T>(val: T) => FetchableValue<T>;
   action: <State, K extends keyof State>(
     // Only allow state fields for fetchable values
     stateField: FetchableValue extends State[K] ? K : never,
     customReducers?: Partial<FetchableReducers<State>>
-  ) => FetchableReducers<State>,
+  ) => FetchableReducers<State>;
 }
 
 interface Dependencies {
@@ -54,13 +60,17 @@ interface Dependencies {
 // if given action is not in keyof Actions
 interface ModelDefinition<State, Actions, Deps> {
   name: string;
-  inject?: string[];
+  inject?: [keyof Deps];
   state: State;
   actions: (
     { initialState }: { initialState: State }
   ) => {
     // Only include those keys that are present in the action's interface
-    [K in keyof Actions]: Reducer<State> | FetchableReducers<State>
+    [K in keyof Actions]: Actions[K] extends FetchableAction<any>
+      ? FetchableReducers<State>
+      : Actions[K] extends Function
+      ? Reducer<State, ArgumentType<Actions[K]>>
+      : never
   };
   reactions?: (
     { initialState, deps }: { initialState: State; deps: Deps }