Fix join/part collapsing regressions (#553)

* Fix join/part collapsing regressions

* Simplify loop

* Explain e,e

* Explain return null in _renderSummary

* Kill it properly

* Move . to _renderSummary

* Only use the first and last events to decide whether a net change has occured

* Do not sort events by TS before summarising

* fix loop and comment

* remove data-number-events

* Better explanation comment in _renderSummary

* Less tortuous comment

src/components/structures/MessagePanel.js

@@ -229,6 +229,7 @@ module.exports = React.createClass({
 
     _getEventTiles: function() {
         var EventTile = sdk.getComponent('rooms.EventTile');
+        var DateSeparator = sdk.getComponent('messages.DateSeparator');
         const MemberEventListSummary = sdk.getComponent('views.elements.MemberEventListSummary');
 
         this.eventNodes = {};
@@ -278,8 +279,8 @@ module.exports = React.createClass({
 
         var isMembershipChange = (e) =>
             e.getType() === 'm.room.member'
-            && ['join', 'leave'].indexOf(e.event.content.membership) !== -1
+            && ['join', 'leave'].indexOf(e.getContent().membership) !== -1
-            && (!e.event.prev_content || e.event.content.membership  !== e.event.prev_content.membership);
+            && (!e.getPrevContent() || e.getContent().membership  !== e.getPrevContent().membership);
 
         for (i = 0; i < this.props.events.length; i++) {
             var mxEv = this.props.events[i];
@@ -294,23 +295,32 @@ module.exports = React.createClass({
 
             // Wrap consecutive member events in a ListSummary
             if (isMembershipChange(mxEv)) {
-                let summarisedEvents = [mxEv];
+                let ts1 = mxEv.getTs();
-                i++;
-                for (;i < this.props.events.length; i++) {
-                    let collapsedMxEv = this.props.events[i];
 
-                    if (!isMembershipChange(collapsedMxEv)) {
+                if (this._wantsDateSeparator(prevEvent, ts1)) {
-                        i--;
+                    let dateSeparator = <li key={ts1+'~'}><DateSeparator key={ts1+'~'} ts={ts1}/></li>;
+                    ret.push(dateSeparator);
+                }
+
+                let summarisedEvents = [mxEv];
+                for (;i + 1 < this.props.events.length; i++) {
+                    let collapsedMxEv = this.props.events[i + 1];
+
+                    if (!isMembershipChange(collapsedMxEv) ||
+                        this._wantsDateSeparator(this.props.events[i], collapsedMxEv.getTs())) {
                         break;
                     }
                     summarisedEvents.push(collapsedMxEv);
                 }
-                // At this point, i = this.props.events.length OR i = the index of the last
+                // At this point, i = the index of the last event in the summary sequence
-                // MembershipChange in a sequence of MembershipChanges
 
                 let eventTiles = summarisedEvents.map(
                     (e) => {
-                        let ret = this._getTilesForEvent(prevEvent, e);
+                        // In order to prevent DateSeparators from appearing in the expanded form
+                        // of MemberEventListSummary, render each member event as if the previous
+                        // one was itself. This way, the timestamp of the previous event === the
+                        // timestamp of the current event, and no DateSeperator is inserted.
+                        let ret = this._getTilesForEvent(e, e);
                         prevEvent = e;
                         return ret;
                     }

src/components/views/avatars/MemberAvatar.js

@@ -69,9 +69,9 @@ module.exports = React.createClass({
     render: function() {
         var BaseAvatar = sdk.getComponent("avatars.BaseAvatar");
 
-        var {member, onClick, ...otherProps} = this.props;
+        var {member, onClick, viewUserOnClick, ...otherProps} = this.props;
 
-        if (this.props.viewUserOnClick) {
+        if (viewUserOnClick) {
             onClick = () => {
                 dispatcher.dispatch({
                     action: 'view_user',

src/components/views/elements/MemberEventListSummary.js

@@ -107,10 +107,20 @@ module.exports = React.createClass({
                 </span>
             );
         }
+
+        // The joinEvents and leaveEvents are representative of the net movement
+        // per-user, and so it is possible that the total net movement is nil,
+        // whilst there are some events in the expanded list. If the total net
+        // movement is nil, then neither joinSummary nor leaveSummary will be
+        // truthy, so return null.
+        if (!joinSummary && !leaveSummary) {
+            return null;
+        }
+
         return (
             <span>
                 {joinSummary}{joinSummary && leaveSummary?'; ':''}
-                {leaveSummary}
+                {leaveSummary}.&nbsp;
             </span>
         );
     },
@@ -140,15 +150,24 @@ module.exports = React.createClass({
         // Reorder events so that joins come before leaves
         let eventsToRender = this.props.events;
 
-        // Filter out those who joined, then left
+        // Create an array of events that are not "cancelled-out" by another
-        let filteredEvents = eventsToRender.filter(
+        // A join of sender S is cancelled out by a leave of sender S etc.
-            (e) => {
+        let filteredEvents = [];
-                return eventsToRender.filter(
+        let senders = new Set(eventsToRender.map((e) => e.getSender()));
-                    (e2) => {
+        senders.forEach(
-                        return e.getSender() === e2.getSender()
+            (userId) => {
-                            && e.event.content.membership !== e2.event.content.membership;
+                // Only push the last event if it isn't the same membership as the first
-                    }
+
-                ).length === 0;
+                let userEvents = eventsToRender.filter((e) => {
+                    return e.getSender() === userId;
+                });
+
+                let firstEvent = userEvents[0];
+                let lastEvent = userEvents[userEvents.length - 1];
+
+                if (firstEvent.getContent().membership !== lastEvent.getContent().membership) {
+                    filteredEvents.push(lastEvent);
+                }
             }
         );
 
@@ -194,7 +213,7 @@ module.exports = React.createClass({
                             {avatars}
                         </span>
                         <span className="mx_TextualEvent mx_MemberEventListSummary_summary">
-                            {summary}{joinAndLeft? '. ' + joinAndLeft + ' ' + noun + ' joined and left' : ''}
+                            {summary}{joinAndLeft ? joinAndLeft + ' ' + noun + ' joined and left' : ''}
                         </span>&nbsp;
                         {toggleButton}
                     </div>