Fix welcome user

https://github.com/matrix-org/matrix-react-sdk/pull/3101 meant we
don't get logged straight in after registering if using an email
address, but this was the point at which we made a chat with the
welcome user. Instead, set a flag in memory that we should try &
make a chat with the welcome user for that user ID if we get a
session for them.

Of course, if the user logs in on both tabs, this would mean each
would make a chat with the welcome user (although actually this
was a problem with the old code too). Check our m.direct to see if
we've started a chat with the welcome user before making one (which
also means we have to make sure the cached sync is up to date...
see comments).

src/MatrixClientPeg.js

@@ -51,6 +51,7 @@ interface MatrixClientCreds {
 class MatrixClientPeg {
     constructor() {
         this.matrixClient = null;
+        this._justRegisteredUserId = null;
 
         // These are the default options used when when the
         // client is started in 'start'. These can be altered
@@ -85,6 +86,31 @@ class MatrixClientPeg {
         MatrixActionCreators.stop();
     }
 
+    /*
+     * If we've registered a user ID we set this to the ID of the
+     * user we've just registered. If they then go & log in, we
+     * can send them to the welcome user (obviously this doesn't
+     * guarentee they'll get a chat with the welcome user).
+     *
+     * @param {string} uid The user ID of the user we've just registered
+     */
+    setJustRegisteredUserId(uid) {
+        this._justRegisteredUserId = uid;
+    }
+
+    /*
+     * Returns true if the current user has just been registered by this
+     * client as determined by setJustRegisteredUserId()
+     *
+     * @returns {bool} True if user has just been registered
+     */
+    currentUserIsJustRegistered() {
+        return (
+            this.matrixClient &&
+            this.matrixClient.credentials.userId === this._justRegisteredUserId
+        );
+    }
+
     /**
      * Replace this MatrixClientPeg's client with a client instance that has
      * homeserver / identity server URLs and active credentials

src/components/structures/MatrixChat.js

@@ -53,6 +53,7 @@ import { messageForSyncError } from '../../utils/ErrorUtils';
 import ResizeNotifier from "../../utils/ResizeNotifier";
 import { ValidatedServerConfig } from "../../utils/AutoDiscoveryUtils";
 import AutoDiscoveryUtils from "../../utils/AutoDiscoveryUtils";
+import DMRoomMap from '../../utils/DMRoomMap';
 
 // Disable warnings for now: we use deprecated bluebird functions
 // and need to migrate, but they spam the console with warnings.
@@ -887,6 +888,7 @@ export default React.createClass({
                     }
                     return;
                 }
+                MatrixClientPeg.setJustRegisteredUserId(credentials.user_id);
                 this.onRegistered(credentials);
             },
             onDifferentServerClicked: (ev) => {
@@ -1134,26 +1136,65 @@ export default React.createClass({
     /**
      * Called when a new logged in session has started
      */
-    _onLoggedIn: async function() {
+    _onLoggedIn: function() {
         this.setStateForNewView({ view: VIEWS.LOGGED_IN });
-        if (this._is_registered) {
-            this._is_registered = false;
+        if (MatrixClientPeg.currentUserIsJustRegistered()) {
+            MatrixClientPeg.setJustRegisteredUserId(null);
 
             if (this.props.config.welcomeUserId && getCurrentLanguage().startsWith("en")) {
-                const roomId = await createRoom({
-                    dmUserId: this.props.config.welcomeUserId,
-                    // Only view the welcome user if we're NOT looking at a room
-                    andView: !this.state.currentRoomId,
-                });
-                // if successful, return because we're already
-                // viewing the welcomeUserId room
-                // else, if failed, fall through to view_home_page
-                if (roomId) {
-                    return;
+                // We can end up with multiple tabs post-registration where the user
+                // might then end up with a session and we don't want them all making
+                // a chat with the welcome user: try to de-dupe.
+                // We need to wait for the first sync to complete for this to
+                // work though.
+                let waitFor;
+                if (!this.firstSyncComplete) {
+                    waitFor = this.firstSyncPromise.promise;
+                } else {
+                    waitFor = Promise.resolve();
                 }
+                waitFor.then(async () => {
+                    const welcomeUserRooms = DMRoomMap.shared().getDMRoomsForUserId(
+                        this.props.config.welcomeUserId,
+                    );
+                    if (welcomeUserRooms.length === 0) {
+                        const roomId = await createRoom({
+                            dmUserId: this.props.config.welcomeUserId,
+                            // Only view the welcome user if we're NOT looking at a room
+                            andView: !this.state.currentRoomId,
+                        });
+                        // This is a bit of a hack, but since the deduplication relies
+                        // on m.direct being up to date, we need to force a sync
+                        // of the database, otherwise if the user goes to the other
+                        // tab before the next save happens (a few minutes), the
+                        // saved sync will be restored from the db and this code will
+                        // run without the update to m.direct, making another welcome
+                        // user room.
+                        const saveWelcomeUser = (ev) => {
+                            if (
+                                ev.getType() == 'm.direct' &&
+                                ev.getContent() &&
+                                ev.getContent()[this.props.config.welcomeUserId]
+                            ) {
+                                MatrixClientPeg.get().store.save(true);
+                                MatrixClientPeg.get().removeListener(
+                                    "accountData", saveWelcomeUser,
+                                );
+                            }
+                        };
+                        MatrixClientPeg.get().on("accountData", saveWelcomeUser);
+
+                        // if successful, return because we're already
+                        // viewing the welcomeUserId room
+                        // else, if failed, fall through to view_home_page
+                        if (roomId) {
+                            return;
+                        }
+                    }
+                    // The user has just logged in after registering
+                    dis.dispatch({action: 'view_home_page'});
+                });
             }
-            // The user has just logged in after registering
-            dis.dispatch({action: 'view_home_page'});
         } else {
             this._showScreenAfterLogin();
         }
@@ -1694,9 +1735,6 @@ export default React.createClass({
                 return MatrixClientPeg.get();
             }
         }
-        // XXX: This should be in state or ideally store(s) because we risk not
-        //      rendering the most up-to-date view of state otherwise.
-        this._is_registered = true;
         return Lifecycle.setLoggedIn(credentials);
     },
 

src/components/structures/auth/Registration.js

@@ -29,6 +29,7 @@ import * as ServerType from '../../views/auth/ServerTypeSelector';
 import AutoDiscoveryUtils, {ValidatedServerConfig} from "../../../utils/AutoDiscoveryUtils";
 import classNames from "classnames";
 import * as Lifecycle from '../../../Lifecycle';
+import MatrixClientPeg from "../../../MatrixClientPeg";
 
 // Phases
 // Show controls to configure server details
@@ -287,6 +288,8 @@ module.exports = React.createClass({
             return;
         }
 
+        MatrixClientPeg.setJustRegisteredUserId(response.user_id);
+
         const newState = {
             doingUIAuth: false,
         };