model: Make REGISTER_COMPLETE reset some state we forgot about

This addresses the second item in the list at zulip#5605:

> - [ ] `REGISTER_COMPLETE` should reset or replace all server data
>       and server-data metadata, but it isn't in some cases:
>       - server data: `topics`, `typing` (should reset)
>       - server-data metadata: `fetching` (should reset)

Although, I've left a comment on `fetchingReducer`, where doing so
felt a bit funny because morally it shouldn't be necessary.

Fixes-partly: zulip#5605

Author: chrisbobbe

src/chat/__tests__/fetchingReducer-test.js

@@ -23,6 +23,15 @@ describe('fetchingReducer', () => {
     expect(fetchingReducer(prevState, eg.action.reset_account_data)).toEqual(initialState);
   });
 
+  test('REGISTER_COMPLETE', () => {
+    const initialState = eg.baseReduxState.fetching;
+    const action1 = { type: MESSAGE_FETCH_START, narrow: HOME_NARROW, numBefore: 10, numAfter: 10 };
+    const prevState = fetchingReducer(initialState, action1);
+    expect(prevState).not.toEqual(initialState);
+
+    expect(fetchingReducer(prevState, eg.action.register_complete)).toEqual(initialState);
+  });
+
   describe('MESSAGE_FETCH_START', () => {
     test('if messages are fetched before or after the corresponding flag is set', () => {
       const prevState = deepFreeze({ [HOME_NARROW_STR]: { older: false, newer: false } });

src/chat/fetchingReducer.js

@@ -5,6 +5,7 @@ import {
   MESSAGE_FETCH_ERROR,
   MESSAGE_FETCH_COMPLETE,
   RESET_ACCOUNT_DATA,
+  REGISTER_COMPLETE,
 } from '../actionConstants';
 import { NULL_OBJECT } from '../nullObjects';
 import { DEFAULT_FETCHING } from './fetchingSelectors';
@@ -69,6 +70,15 @@ export default (
     case RESET_ACCOUNT_DATA:
       return initialState;
 
+    // Reset just because `fetching` is server-data metadata, and we're
+    // resetting the server data it's supposed to apply to… But really, we
+    // should have canceled any in-progress message fetches by now; that's
+    // #5623. Still, even if there is an in-progress fetch, we probably
+    // don't want to show loading indicators for it in the UI.
+    // TODO(#5623): Remove reference to #5623.
+    case REGISTER_COMPLETE:
+      return initialState;
+
     case MESSAGE_FETCH_START:
       return messageFetchStart(state, action);
 

src/topics/__tests__/topicsReducer-test.js

@@ -8,6 +8,14 @@ import { INIT_TOPICS } from '../../actionConstants';
 import { NULL_OBJECT } from '../../nullObjects';
 
 describe('topicsReducer', () => {
+  describe('REGISTER_COMPLETE', () => {
+    test('resets state to initial state', () => {
+      const prevState = deepFreeze({ [eg.stream.stream_id]: [{ max_id: 1, name: 'some topic' }] });
+      const action = eg.action.register_complete;
+      expect(topicsReducer(prevState, action)).toEqual(eg.baseReduxState.topics);
+    });
+  });
+
   describe('RESET_ACCOUNT_DATA', () => {
     test('resets state to initial state', () => {
       const prevState = deepFreeze({ [eg.stream.stream_id]: [{ max_id: 1, name: 'some topic' }] });

src/topics/topicsReducer.js

@@ -1,6 +1,11 @@
 /* @flow strict-local */
 import type { TopicsState, PerAccountApplicableAction } from '../types';
-import { INIT_TOPICS, EVENT_NEW_MESSAGE, RESET_ACCOUNT_DATA } from '../actionConstants';
+import {
+  INIT_TOPICS,
+  EVENT_NEW_MESSAGE,
+  REGISTER_COMPLETE,
+  RESET_ACCOUNT_DATA,
+} from '../actionConstants';
 import { NULL_OBJECT } from '../nullObjects';
 import { replaceItemInArray } from '../utils/immutability';
 
@@ -44,6 +49,10 @@ export default (
     case RESET_ACCOUNT_DATA:
       return initialState;
 
+    // Reset to clear stale data; payload has no initial data for this model
+    case REGISTER_COMPLETE:
+      return initialState;
+
     case INIT_TOPICS:
       return {
         ...state,

src/typing/__tests__/typingReducer-test.js

@@ -46,6 +46,23 @@ describe('typingReducer', () => {
     expect(typingReducer(prevState, eg.action.reset_account_data)).toEqual(initialState);
   });
 
+  describe('REGISTER_COMPLETE', () => {
+    test('resets state to initial state', () => {
+      const initialState = eg.baseReduxState.typing;
+      const action1 = egTypingAction({
+        op: 'start',
+        sender: user1,
+        recipients: [user1, eg.selfUser],
+        time: 123456889,
+      });
+      const prevState = typingReducer(initialState, action1);
+      expect(prevState).not.toEqual(initialState);
+
+      const action2 = eg.action.register_complete;
+      expect(typingReducer(prevState, action2)).toEqual(eg.baseReduxState.typing);
+    });
+  });
+
   describe('EVENT_TYPING_START', () => {
     test('adds sender as currently typing user', () => {
       const prevState = NULL_OBJECT;

src/typing/typingReducer.js

@@ -6,6 +6,7 @@ import {
   CLEAR_TYPING,
   DEAD_QUEUE,
   RESET_ACCOUNT_DATA,
+  REGISTER_COMPLETE,
 } from '../actionConstants';
 import { pmTypingKeyFromRecipients } from '../utils/recipient';
 import { NULL_OBJECT } from '../nullObjects';
@@ -99,6 +100,10 @@ export default (
     case RESET_ACCOUNT_DATA:
       return initialState;
 
+    // Reset to clear stale data; payload has no initial data for this model
+    case REGISTER_COMPLETE:
+      return initialState;
+
     default:
       return state;
   }