navSelectors: Remove, after inlining last remaining function.

As mentioned in a previous commit, navSelectors and navActions are
kind of relics from before zulip#3804, and we already have zulip#4417 for
removing most or all of navActions.

Might as well remove navSelectors.

src/nav/__tests__/navSelectors-test.js → src/nav/__tests__/navActions-test.js

@@ -1,10 +1,10 @@
 /* @flow strict-local */
 import deepFreeze from 'deep-freeze';
 
-import { getSameRoutesCount } from '../navSelectors';
+import { navigateBack } from '../navActions';
 import * as NavigationService from '../NavigationService';
 
-describe('getSameRoutesCount', () => {
+describe('navigateBack', () => {
   test('if no routes the count of same routes is 0', () => {
     // $FlowFixMe[cannot-write] Make Flow understand about mocking.
     NavigationService.getState = jest.fn().mockReturnValue(
@@ -13,9 +13,9 @@ describe('getSameRoutesCount', () => {
       }),
     );
 
-    const count = getSameRoutesCount();
+    const action = navigateBack();
 
-    expect(count).toEqual(0);
+    expect(action.payload.count).toEqual(0);
   });
 
   test('if last route differs from  routes the count of same routes is 0', () => {
@@ -26,9 +26,9 @@ describe('getSameRoutesCount', () => {
       }),
     );
 
-    const count = getSameRoutesCount();
+    const action = navigateBack();
 
-    expect(count).toEqual(1);
+    expect(action.payload.count).toEqual(1);
   });
 
   test('if several of the routes are the same ignore the params and return their count', () => {
@@ -45,8 +45,8 @@ describe('getSameRoutesCount', () => {
       }),
     );
 
-    const count = getSameRoutesCount();
+    const action = navigateBack();
 
-    expect(count).toEqual(3);
+    expect(action.payload.count).toEqual(3);
   });
 });

src/nav/navActions.js

@@ -6,11 +6,22 @@ import {
   type GenericNavigationAction,
 } from '@react-navigation/native';
 
+import * as NavigationService from './NavigationService';
 import type { Message, Narrow, SharedData, UserId } from '../types';
 import type { ApiResponseServerSettings } from '../api/settings/getServerSettings';
-import { getSameRoutesCount } from '../selectors';
 
-export const navigateBack = (): PopAction => StackActions.pop(getSameRoutesCount());
+export const navigateBack = (): PopAction => {
+  const routes = NavigationService.getState().routes;
+  let i = routes.length - 1;
+  while (i >= 0) {
+    if (routes[i].name !== routes[routes.length - 1].name) {
+      break;
+    }
+    i--;
+  }
+  const sameRoutesCount = routes.length - i - 1;
+  return StackActions.pop(sameRoutesCount);
+};
 
 /*
  * "Reset" actions, to explicitly prohibit back navigation.

src/selectors.js

@@ -7,7 +7,6 @@ export * from './chat/fetchingSelectors';
 export * from './directSelectors';
 export * from './emoji/emojiSelectors';
 export * from './message/messageSelectors';
-export * from './nav/navSelectors';
 export * from './subscriptions/subscriptionSelectors';
 export * from './topics/topicSelectors';
 export * from './typing/typingSelectors';