Add getRelation helper

This adds a `getRelation` helper to ensure we always read relation info from the
wire content as required in E2E rooms.

src/models/event-timeline-set.js

@@ -719,9 +719,8 @@ EventTimelineSet.prototype._aggregateRelations = function(event) {
         return;
     }
 
-    const content = event.getContent();
+    const relation = event.getRelation();
-    const relation = content && content["m.relates_to"];
+    if (!relation) {
-    if (!relation || !relation.rel_type || !relation.event_id) {
         return;
     }
 

src/models/event.js

@@ -735,20 +735,34 @@ utils.extend(module.exports.MatrixEvent.prototype, {
     },
 
     /**
-     * Get whether the event is a relation event, and of a given type if `relType` is passed in.
+     * Get whether the event is a relation event, and of a given type if
+     * `relType` is passed in.
      *
-     * @param {string?} relType if given, checks that the relation is of the given type
+     * @param {string?} relType if given, checks that the relation is of the
+     * given type
      * @return {boolean}
      */
     isRelation(relType = undefined) {
-        // must use event.content as m.relates_to is not encrypted
+        // Relation info is lifted out of the encrypted content when sent to
-        // and _clearEvent doesn't have it.
+        // encrypted rooms, so we have to check `getWireContent` for this.
-        const content = this.event.content;
+        const content = this.getWireContent();
         const relation = content && content["m.relates_to"];
         return relation && relation.rel_type && relation.event_id &&
             ((relType && relation.rel_type === relType) || !relType);
     },
 
+    /**
+     * Get relation info for the event, if any.
+     *
+     * @return {Object}
+     */
+    getRelation() {
+        if (!this.isRelation()) {
+            return null;
+        }
+        return this.getWireContent()["m.relates_to"];
+    },
+
     /**
      * Set an event that replaces the content of this event, through an m.replace relation.
      *
@@ -768,11 +782,7 @@ utils.extend(module.exports.MatrixEvent.prototype, {
         }
         const oldContent = this.getContent();
         const newContent = newEvent.getContent()["m.new_content"];
-        // need to always replace m.relates_to with the old one,
+        Object.assign(oldContent, newContent);
-        // even if there is none, as the m.replace relation should
-        // not be exposed on the target event m.relates_to (that's what the server does).
-        Object.assign(oldContent, newContent,
-            {"m.relates_to": oldContent["m.relates_to"]});
         this._replacingEvent = newEvent;
     },
 

src/models/relations.js

@@ -52,9 +52,8 @@ export default class Relations extends EventEmitter {
      * The new relation event to be aggregated.
      */
     addEvent(event) {
-        const content = event.getContent();
+        const relation = event.getRelation();
-        const relation = content && content["m.relates_to"];
+        if (!relation) {
-        if (!relation || !relation.rel_type || !relation.event_id) {
             console.error("Event must have relation info");
             return;
         }
@@ -139,8 +138,7 @@ export default class Relations extends EventEmitter {
 
         if (this.relationType === "m.annotation") {
             // Remove the redacted annotation from aggregation by key
-            const content = redactedEvent.getContent();
+            const relation = redactedEvent.getRelation();
-            const relation = content && content["m.relates_to"];
             if (!relation) {
                 return;
             }

src/models/room.js

@@ -1034,7 +1034,7 @@ Room.prototype._addLiveEvent = function(event, duplicateStrategy) {
 
 
     if (this._opts.unstableClientRelationReplacements && event.isRelation("m.replace")) {
-        const relatesTo = event.getContent()["m.relates_to"];
+        const relatesTo = event.getRelation();
         const replacedId = relatesTo && relatesTo.event_id;
         const replacedEvent = this.getUnfilteredTimelineSet().findEventById(replacedId);
         if (replacedEvent) {