fix: don't merge state with existing state during reset. fixes #111

packages/core/src/BaseRouter.tsx

@@ -1,5 +1,5 @@
 import shortid from 'shortid';
-import { CommonAction, NavigationState } from './types';
+import { CommonAction, NavigationState, PartialState } from './types';
 
 /**
  * Base router object that can be used when writing custom routers.
@@ -9,7 +9,7 @@ const BaseRouter = {
   getStateForAction<State extends NavigationState>(
     state: State,
     action: CommonAction
-  ): State | null {
+  ): State | PartialState<State> | null {
     switch (action.type) {
       case 'REPLACE': {
         const index = action.source
@@ -56,12 +56,7 @@ const BaseRouter = {
       }
 
       case 'RESET':
-        return {
-          ...state,
-          ...action.payload,
-          key: state.key,
-          routeNames: state.routeNames,
-        };
+        return action.payload as PartialState<State>;
 
       default:
         return null;

packages/core/src/NavigationContainer.tsx

@@ -24,7 +24,9 @@ const MISSING_CONTEXT_ERROR =
 export const NavigationStateContext = React.createContext<{
   state?: NavigationState | PartialState<NavigationState>;
   getState: () => NavigationState | PartialState<NavigationState> | undefined;
-  setState: (state: NavigationState | undefined) => void;
+  setState: (
+    state: NavigationState | PartialState<NavigationState> | undefined
+  ) => void;
   key?: string;
   performTransaction: (action: () => void) => void;
 }>({

packages/core/src/SceneView.tsx

@@ -47,7 +47,7 @@ export default function SceneView<
   }, [getState, route.key]);
 
   const setCurrentState = React.useCallback(
-    (child: NavigationState | undefined) => {
+    (child: NavigationState | PartialState<NavigationState> | undefined) => {
       const state = getState();
 
       setState({

packages/core/src/__tests__/BaseRouter.test.tsx

@@ -125,15 +125,5 @@ it('resets state to new state with RESET', () => {
     })
   );
 
-  expect(result).toEqual({ ...STATE, index: 0, routes });
-});
-
-it('ignores key and routeNames when resetting with RESET', () => {
-  const result = BaseRouter.getStateForAction(
-    STATE,
-    // @ts-ignore
-    CommonActions.reset({ index: 2, key: 'foo', routeNames: ['test'] })
-  );
-
-  expect(result).toEqual({ ...STATE, index: 2 });
+  expect(result).toEqual({ index: 0, routes });
 });

packages/core/src/types.tsx

@@ -170,7 +170,10 @@ export type Router<
    * @param state State object to apply the action on.
    * @param action Action object to apply.
    */
-  getStateForAction(state: State, action: Action): State | null;
+  getStateForAction(
+    state: State,
+    action: Action
+  ): State | PartialState<State> | null;
 
   /**
    * Whether the action should also change focus in parent navigator

packages/core/src/useOnAction.tsx

@@ -2,13 +2,18 @@ import * as React from 'react';
 import NavigationBuilderContext, {
   ChildActionListener,
 } from './NavigationBuilderContext';
-import { NavigationAction, NavigationState, Router } from './types';
+import {
+  NavigationAction,
+  NavigationState,
+  PartialState,
+  Router,
+} from './types';
 
 type Options = {
   router: Router<NavigationState, NavigationAction>;
   key?: string;
   getState: () => NavigationState;
-  setState: (state: NavigationState) => void;
+  setState: (state: NavigationState | PartialState<NavigationState>) => void;
   listeners: ChildActionListener[];
 };