nav: Stop using react-navigation-redux-helpers.

We've long used Redux to manage our navigation state, with a helper
package called react-navigation-redux-helpers. React Navigation has
recommended against this for quite some time.

In this commit:

- Stop using r-n-r-h's `createReduxContainer`, and use React
  Navigation's own `createAppContainer` instead.

  - Rename `AppWithNavigation` (arguably better named
    `ReduxContainer` before this commit) to `AppContainer`

  - Rename `NavigationService.reduxContainerRef` to
    `NavigationService.appContainerRef` and change some of
    `NavigationService`'s implementation details to handle the new
    shape.

- Remove use of `createReactNavigationReduxMiddleware`.

- Remove `state.nav`.

  - Remove `navReducer`.

  - Adjust types as necessary.

  - Remove 'nav' from `discardKeys` in src/boot/store.js

Fixes: zulip#3804

src/ZulipMobile.js

@@ -11,7 +11,7 @@ import AppEventHandlers from './boot/AppEventHandlers';
 import AppDataFetcher from './boot/AppDataFetcher';
 import BackNavigationHandler from './nav/BackNavigationHandler';
 import InitialNavigationDispatcher from './nav/InitialNavigationDispatcher';
-import AppWithNavigation from './nav/AppWithNavigation';
+import AppContainer from './nav/AppContainer';
 import NavigationService from './nav/NavigationService';
 
 import './i18n/locale';
@@ -31,7 +31,12 @@ export default (): React$Node => (
             <ThemeProvider>
               <InitialNavigationDispatcher>
                 <BackNavigationHandler>
-                  <AppWithNavigation ref={NavigationService.reduxContainerRef} />
+                  <AppContainer
+                    // `static navigationOptions` and `static router` not
+                    // being handled properly
+                    // $FlowFixMe
+                    ref={NavigationService.appContainerRef}
+                  />
                 </BackNavigationHandler>
               </InitialNavigationDispatcher>
             </ThemeProvider>

src/boot/reducers.js

@@ -17,7 +17,6 @@ import flags from '../chat/flagsReducer';
 import narrows from '../chat/narrowsReducer';
 import messages from '../message/messagesReducer';
 import mute from '../mute/muteReducer';
-import nav from '../nav/navReducer';
 import outbox from '../outbox/outboxReducer';
 import presence from '../presence/presenceReducer';
 import realm from '../realm/realmReducer';
@@ -46,7 +45,6 @@ const reducers = {
   messages,
   narrows,
   mute,
-  nav,
   outbox,
   presence,
   realm,

src/boot/store.js

@@ -4,7 +4,6 @@ import type { Store } from 'redux';
 import thunkMiddleware from 'redux-thunk';
 import { createLogger } from 'redux-logger';
 import createActionBuffer from 'redux-action-buffer';
-import { createReactNavigationReduxMiddleware } from 'react-navigation-redux-helpers';
 import Immutable from 'immutable';
 import * as Serialize from 'remotedev-serialize';
 import { persistStore, autoRehydrate } from '../third/redux-persist';
@@ -29,7 +28,7 @@ import createMigration from '../redux-persist-migrate/index';
 // prettier-ignore
 export const discardKeys: Array<$Keys<GlobalState>> = [
   'alertWords', 'caughtUp', 'fetching',
-  'nav', 'presence', 'session', 'topics', 'typing', 'userStatus',
+  'presence', 'session', 'topics', 'typing', 'userStatus',
 ];
 
 /**
@@ -209,10 +208,6 @@ const migrations: { [string]: (GlobalState) => GlobalState } = {
  */
 function listMiddleware() {
   const result = [
-    // Allow us to cause navigation by dispatching Redux actions.
-    // See docs: https://github.com/react-navigation/redux-helpers
-    createReactNavigationReduxMiddleware((state: GlobalState) => state.nav, 'root'),
-
     // Delay ("buffer") actions until a REHYDRATE action comes through.
     // After dispatching the latter, this will go back and dispatch
     // all the buffered actions.  See docs:

src/nav/AppContainer.js

@@ -0,0 +1,7 @@
+/* @flow strict-local */
+import { createAppContainer } from 'react-navigation';
+import type { NavigationState } from 'react-navigation';
+
+import AppNavigator from './AppNavigator';
+
+export default createAppContainer<NavigationState, { ... }>(AppNavigator);

src/nav/NavigationService.js

@@ -2,53 +2,38 @@
 import React from 'react';
 import type {
   NavigationAction,
-  NavigationNavigatorProps,
   NavigationState,
-  NavigationDispatch,
-  SupportedThemes,
+  NavigationContainer,
+  NavigationContainerProps,
 } from 'react-navigation';
 
-type ReduxContainerProps = {
-  ...$Diff<NavigationNavigatorProps<{ ... }, NavigationState>, { navigation: mixed }>,
-  state: NavigationState,
-  dispatch: NavigationDispatch,
-  theme: SupportedThemes | 'no-preference',
-};
-
-// Should mimic return type of react-navigation-redux-helpers's
-// `createReduxContainer`.
-type ReduxContainer = React$Component<ReduxContainerProps>;
-
-// TODO: This will eventually be a ref to the component instance
-// created by React Navigation's `createAppContainer`, not
-// react-navigation-redux-helpers's `createReduxContainer`.
-const reduxContainerRef = React.createRef<ReduxContainer>();
+const appContainerRef = React.createRef<
+  NavigationContainer<NavigationState, { ... }, NavigationContainerProps<{ ... }, NavigationState>>,
+>();
 
 const getState = (): NavigationState => {
-  if (reduxContainerRef.current === null) {
-    throw new Error('Tried to use NavigationService before reduxContainerRef was set.');
+  if (appContainerRef.current === null) {
+    throw new Error('Tried to use NavigationService before appContainerRef was set.');
   }
   return (
-    reduxContainerRef.current
-      // $FlowFixMe - how to tell Flow about this method?
-      .getCurrentNavigation().state
+    // $FlowFixMe - how to tell Flow about `.state`?
+    appContainerRef.current.state.nav
   );
 };
 
 const dispatch = (navigationAction: NavigationAction): boolean => {
-  if (reduxContainerRef.current === null) {
-    throw new Error('Tried to use NavigationService before reduxContainerRef was set.');
+  if (appContainerRef.current === null) {
+    throw new Error('Tried to use NavigationService before appContainerRef was set.');
   }
   return (
-    reduxContainerRef.current
+    appContainerRef.current
       // $FlowFixMe - how to tell Flow about this method?
-      .getCurrentNavigation()
       .dispatch(navigationAction)
   );
 };
 
 export default {
   getState,
   dispatch,
-  reduxContainerRef,
+  appContainerRef,
 };

src/reduxTypes.js

@@ -196,13 +196,6 @@ export type NavigationRouteState = {
   },
 };
 
-export type NavigationState = {|
-  index: number,
-  isTransitioning: boolean,
-  key: string,
-  routes: NavigationRouteState[],
-|};
-
 export type OutboxState = Outbox[];
 
 /**
@@ -358,7 +351,6 @@ export type GlobalState = {|
   migrations: MigrationsState,
   mute: MuteState,
   narrows: NarrowsState,
-  nav: NavigationState,
   outbox: OutboxState,
   presence: PresenceState,
   realm: RealmState,