Add thread relation in sendEvent if it's missing (#2149)

Author: Germain

src/client.ts

@@ -3593,6 +3593,22 @@ export class MatrixClient extends EventEmitter {
             eventType = threadId;
             threadId = null;
         }
+
+        if (threadId && content["m.relates_to"]?.rel_type !== RelationType.Thread) {
+            content["m.relates_to"] = {
+                ...content["m.relates_to"],
+                "rel_type": RelationType.Thread,
+                "event_id": threadId,
+            };
+
+            const thread = this.getRoom(roomId)?.threads.get(threadId);
+            if (thread) {
+                content["m.relates_to"]["m.in_reply_to"] = {
+                    "event_id": thread.replyToEvent.getId(),
+                };
+            }
+        }
+
         return this.sendCompleteEvent(roomId, threadId, { type: eventType, content }, txnId as string, callback);
     }
 
@@ -4213,17 +4229,6 @@ export class MatrixClient extends EventEmitter {
             body: text,
         };
 
-        const thread = this.getRoom(roomId)?.threads.get(threadId);
-        if (thread) {
-            content["m.relates_to"] = {
-                "rel_type": RelationType.Thread,
-                "event_id": threadId,
-                "m.in_reply_to": {
-                    "event_id": thread.replyToEvent.getId(),
-                },
-            };
-        }
-
         return this.sendEvent(roomId, threadId, EventType.Sticker, content, undefined, callback);
     }