FIX: improvements to chat message streaming (#26892)

- prevents re-rendering avatars while updating messages quickly in the thread preview indicator
- ensures the cancel button is shown when you are admin OR when the streamed message is a reply to the current user

plugins/chat/assets/javascripts/discourse/components/chat-message.gjs

@@ -492,7 +492,7 @@ export default class ChatMessage extends Component {
     return (
       this.args.message.streaming &&
       (this.currentUser.admin ||
-        this.args.message.user.id === this.currentUser.id)
+        this.args.message.inReplyTo?.user?.id === this.currentUser.id)
     );
   }
 

plugins/chat/assets/javascripts/discourse/lib/chat-channel-subscription-manager.js

@@ -234,7 +234,11 @@ export default class ChatChannelSubscriptionManager {
   handleThreadOriginalMessageUpdate(data) {
     const message = this.messagesManager.findMessage(data.original_message_id);
     if (message?.thread) {
-      message.thread.preview = ChatThreadPreview.create(data.preview);
+      if (message.thread.preview) {
+        message.thread.preview.update(data.preview);
+      } else {
+        message.thread.preview = ChatThreadPreview.create(data.preview);
+      }
     }
   }
 }

plugins/chat/assets/javascripts/discourse/models/chat-thread-preview.js

@@ -1,5 +1,4 @@
 import { tracked } from "@glimmer/tracking";
-import { TrackedArray } from "@ember-compat/tracked-built-ins";
 
 export default class ChatThreadPreview {
   static create(args = {}) {
@@ -19,21 +18,37 @@ export default class ChatThreadPreview {
       args = {};
     }
 
+    this.update(args);
+  }
+
+  get otherParticipantCount() {
+    return this.participantCount - this.participantUsers.length;
+  }
+
+  update(args = {}) {
     this.replyCount = args.reply_count || args.replyCount || 0;
     this.lastReplyId = args.last_reply_id || args.lastReplyId;
     this.lastReplyCreatedAt = new Date(
       args.last_reply_created_at || args.lastReplyCreatedAt
     );
     this.lastReplyExcerpt = args.last_reply_excerpt || args.lastReplyExcerpt;
-    this.lastReplyUser = args.last_reply_user || args.lastReplyUser;
     this.participantCount =
       args.participant_count || args.participantCount || 0;
-    this.participantUsers = new TrackedArray(
-      args.participant_users || args.participantUsers || []
-    );
-  }
 
-  get otherParticipantCount() {
-    return this.participantCount - this.participantUsers.length;
+    // cheap trick to avoid avatars flickering
+    const lastReplyUser = args.last_reply_user || args.lastReplyUser;
+    if (lastReplyUser?.id !== this.lastReplyUser?.id) {
+      this.lastReplyUser = lastReplyUser;
+    }
+
+    // cheap trick to avoid avatars flickering
+    const participantUsers =
+      args.participant_users || args.participantUsers || [];
+    if (
+      participantUsers?.map((u) => u.id).join(",") !==
+      this.participantUsers?.map((u) => u.id).join(",")
+    ) {
+      this.participantUsers = participantUsers;
+    }
   }
 }

plugins/chat/test/javascripts/components/chat-message-test.js

@@ -1,5 +1,5 @@
 import { getOwner } from "@ember/application";
-import { render } from "@ember/test-helpers";
+import { clearRender, render } from "@ember/test-helpers";
 import hbs from "htmlbars-inline-precompile";
 import { module, test } from "qunit";
 import { setupRenderingTest } from "discourse/tests/helpers/component-test";
@@ -58,4 +58,56 @@ module("Discourse Chat | Component | chat-message", function (hooks) {
       "has the correct css class"
     );
   });
+
+  test("Message with streaming", async function (assert) {
+    // admin
+    this.currentUser.admin = true;
+
+    this.message = new ChatFabricators(getOwner(this)).message({
+      inReplyTo: new ChatFabricators(getOwner(this)).message(),
+      streaming: true,
+    });
+    await this.message.cook();
+    await render(template);
+
+    assert
+      .dom(".stop-streaming-btn")
+      .exists("when admin, it has the stop streaming button");
+
+    await clearRender();
+
+    // not admin - not replying to current user
+    this.currentUser.admin = false;
+
+    this.message = new ChatFabricators(getOwner(this)).message({
+      inReplyTo: new ChatFabricators(getOwner(this)).message(),
+      streaming: true,
+    });
+    await this.message.cook();
+    await render(template);
+
+    assert
+      .dom(".stop-streaming-btn")
+      .doesNotExist("when admin, it doesn't have the stop streaming button");
+
+    await clearRender();
+
+    // not admin - replying to current user
+    this.currentUser.admin = false;
+
+    this.message = new ChatFabricators(getOwner(this)).message({
+      inReplyTo: new ChatFabricators(getOwner(this)).message({
+        user: this.currentUser,
+      }),
+      streaming: true,
+    });
+    await this.message.cook();
+    await render(template);
+
+    assert
+      .dom(".stop-streaming-btn")
+      .exists(
+        "when replying to current user, it has the stop streaming button"
+      );
+  });
 });