MM-14800 Fix missing messages when switching to a team not previously…

… loaded (mattermost#2562)

* Check that this.props.posts is not null when loading more posts

* Fix isChannelLoading to prevent race condition while switching teams

* Remove unnecesary variable

components/post_view/index.js

@@ -8,7 +8,7 @@ import {withRouter} from 'react-router-dom';
 import {getPosts, getPostsAfter, getPostsBefore, getPostThread} from 'mattermost-redux/actions/posts';
 import {getChannel} from 'mattermost-redux/selectors/entities/channels';
 import {makeGetPostsAroundPost, makeGetPostsInChannel} from 'mattermost-redux/selectors/entities/posts';
-import {getCurrentUserId} from 'mattermost-redux/selectors/entities/users';
+import {getCurrentUserId, getUser} from 'mattermost-redux/selectors/entities/users';
 import {getTeamByName} from 'mattermost-redux/selectors/entities/teams';
 
 import {increasePostVisibility} from 'actions/post_actions.jsx';
@@ -21,17 +21,18 @@ import PostList from './post_list.jsx';
 // This function is added as a fail safe for the channel sync issue we have.
 // When the user switches to a team for the first time we show the channel of previous team and then settle for the right channel after that
 // This causes the scroll correction etc an issue because post_list is not mounted for new channel instead it is updated
-const isChannelLoading = (params, channel, team) => {
+const isChannelLoading = (params, channel, team, teammate) => {
  if (params.postid) {
  return false;
  }
 
  if (channel && team) {
- if (channel.type !== Constants.DM_CHANNEL && channel.type !== Constants.GM_CHANNEL) {
- if (channel.name !== params.identifier) {
-  return true;
- }
+ if (channel.type !== Constants.DM_CHANNEL && channel.name !== params.identifier) {
+ return true;
+ } else if (channel.type === Constants.DM_CHANNEL && teammate && params.identifier !== `@${teammate.username}`) {
+ return true;
  }
+
  if (channel.team_id && channel.team_id !== team.id) {
  return true;
  }
@@ -59,8 +60,12 @@ function makeMapStateToProps() {
 
  const channel = getChannel(state, ownProps.channelId);
  const team = getTeamByName(state, ownProps.match.params.team);
+ let teammate;
+ if (channel.type === Constants.DM_CHANNEL && channel.teammate_id) {
+ teammate = getUser(state, channel.teammate_id);
+ }
 
- const channelLoading = isChannelLoading(ownProps.match.params, channel, team);
+ const channelLoading = isChannelLoading(ownProps.match.params, channel, team, teammate);
  const lastViewedAt = state.views.channel.lastChannelViewTime[ownProps.channelId];
  const {postIds, postsObjById} = preparePostIdsForPostList(state, {posts, lastViewedAt, indicateNewMessages: true});
 

components/post_view/post_list.jsx

@@ -112,6 +112,7 @@ export default class PostList extends React.PureComponent {
 
  this.loadingPosts = false;
  this.extraPagesLoaded = 0;
+
  const channelIntroMessage = PostListRowListIds.CHANNEL_INTRO_MESSAGE;
  const isMobile = Utils.isMobile();
  this.state = {
@@ -260,7 +261,7 @@ export default class PostList extends React.PureComponent {
  }
  } else {
  this.loadingPosts = false;
- if (this.mounted) {
+ if (this.mounted && this.props.posts) {
  const atEnd = !moreToLoad && this.props.posts.length < this.props.postVisibility;
  const newState = {
  atEnd,