From f9defd5afb171870aa015fd9c40e91adfa8ffe3b Mon Sep 17 00:00:00 2001
From: Harry Yu <hy.harry.yu@gmail.com>
Date: Thu, 12 Dec 2019 17:08:41 -0800
Subject: [PATCH] fix: avoid error when updateNextStateHistory called with
 state

---
 packages/core/src/routers/SwitchRouter.js           |  6 +++++-
 .../core/src/routers/__tests__/SwitchRouter-test.js | 13 +++++++++++++
 .../core/src/routers/__tests__/routerTestHelper.js  | 11 +++++++----
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/packages/core/src/routers/SwitchRouter.js b/packages/core/src/routers/SwitchRouter.js
index a0c406b7..294e3139 100644
--- a/packages/core/src/routers/SwitchRouter.js
+++ b/packages/core/src/routers/SwitchRouter.js
@@ -82,7 +82,10 @@ export default (routeConfigs, config = {}) => {
 
   function getNextState(action, prevState, possibleNextState) {
     function updateNextStateHistory(prevState, nextState) {
-      if (backBehavior !== 'history' || nextState.index === prevState.index) {
+      if (
+        backBehavior !== 'history' ||
+        (prevState && nextState && nextState.index === prevState.index)
+      ) {
         return nextState;
       }
       let nextRouteKeyHistory = prevState ? prevState.routeKeyHistory : [];
@@ -104,6 +107,7 @@ export default (routeConfigs, config = {}) => {
     let nextState = possibleNextState;
     if (
       prevState &&
+      possibleNextState &&
       prevState.index !== possibleNextState.index &&
       resetOnBlur
     ) {
diff --git a/packages/core/src/routers/__tests__/SwitchRouter-test.js b/packages/core/src/routers/__tests__/SwitchRouter-test.js
index 5b0606bf..91423858 100644
--- a/packages/core/src/routers/__tests__/SwitchRouter-test.js
+++ b/packages/core/src/routers/__tests__/SwitchRouter-test.js
@@ -231,6 +231,19 @@ describe('SwitchRouter', () => {
     navigateTo('Home');
     expect(getSubState(1).routeName).toEqual('Home');
   });
+
+  it('does not error for a nested navigate action in an uninitialized history router', () => {
+    const { navigateTo, getSubState } = getRouterTestHelper(
+      getExampleRouter({ backBehavior: 'history' }),
+      { skipInitializeState: true }
+    );
+
+    navigateTo('B', {
+      action: NavigationActions.navigate({ routeName: 'B2' }),
+    });
+    expect(getSubState(1).routeName).toEqual('B');
+    expect(getSubState(2).routeName).toEqual('B2');
+  });
 });
 
 const getExampleRouter = (config = {}) => {
diff --git a/packages/core/src/routers/__tests__/routerTestHelper.js b/packages/core/src/routers/__tests__/routerTestHelper.js
index 3ac1eb57..c4f766c4 100644
--- a/packages/core/src/routers/__tests__/routerTestHelper.js
+++ b/packages/core/src/routers/__tests__/routerTestHelper.js
@@ -6,12 +6,15 @@ import * as SwitchActions from '../../routers/SwitchActions';
 // it's often convenient to manipulate a structure that keeps the router state to avoid
 // creating many state1, state2, state3 local variables which are prone to typos...
 
-const defaultInitAction = {
-  type: NavigationActions.INIT,
+const defaultOptions = {
+  skipInitializeState: false,
 };
 
-export const getRouterTestHelper = (router, initAction = defaultInitAction) => {
-  let state = router.getStateForAction(initAction);
+export const getRouterTestHelper = (router, options = defaultOptions) => {
+  let state =
+    options && options.skipInitializeState
+      ? undefined
+      : router.getStateForAction({ type: NavigationActions.INIT });
 
   const applyAction = action => {
     state = router.getStateForAction(action, state);