DEV: Asyncify loadTopicView (#18585)

See https://github.com/discourse/discourse/pull/14838#issuecomment-1271935405 for details about `controllerReady` logic.

Co-authored-by: David Taylor <david@taylorhq.com>

app/assets/javascripts/discourse/app/models/topic.js

@@ -24,7 +24,7 @@ import DiscourseURL, { userPath } from "discourse/lib/url";
 import deprecated from "discourse-common/lib/deprecated";
 import { applyModelTransformations } from "discourse/lib/model-transformers";
 
-export function loadTopicView(topic, args) {
+export async function loadTopicView(topic, args) {
   const data = deepMerge({}, args);
   const url = `${getURL("/t/")}${topic.id}`;
   const jsonUrl = (data.nearPost ? `${url}/${data.nearPost}` : url) + ".json";
@@ -33,12 +33,12 @@ export function loadTopicView(topic, args) {
   delete data.__type;
   delete data.store;
 
-  return PreloadStore.getAndRemove(`topic_${topic.id}`, () =>
+  const json = await PreloadStore.getAndRemove(`topic_${topic.id}`, () =>
     ajax(jsonUrl, { data })
-  ).then((json) => {
-    topic.updateFromJson(json);
-    return json;
-  });
+  );
+
+  topic.updateFromJson(json);
+  return json;
 }
 
 export const ID_CONSTRAINT = /^\d+$/;

app/assets/javascripts/discourse/app/routes/topic-from-params.js

@@ -80,6 +80,7 @@ export default DiscourseRoute.extend({
       enteredAt: Date.now().toString(),
       userLastReadPostNumber: topic.last_read_post_number,
       highestPostNumber: topic.highest_post_number,
+      controllerReady: true,
     });
 
     this.appEvents.trigger("page:topic-loaded", topic);

app/assets/javascripts/discourse/app/routes/topic.js

@@ -23,6 +23,7 @@ const TopicRoute = DiscourseRoute.extend({
       isTransitioning: false,
       scheduledReplace: null,
       lastScrollPos: null,
+      controllerReady: true,
     });
   },
 

app/assets/javascripts/discourse/app/templates/topic.hbs

@@ -13,7 +13,7 @@
 
   <PluginOutlet @name="topic-above-post-stream" @tagName="span" @connectorTagName="div" @args={{hash model=this.model editFirstPost=(action "editFirstPost")}} />
 
-  {{#if this.model.postStream.loaded}}
+  {{#if (and this.controllerReady this.model.postStream.loaded)}}
     {{#if this.model.postStream.firstPostPresent}}
       <TopicTitle @cancelled={{action "cancelEditingTopic"}} @save={{action "finishedEditingTopic"}} @model={{this.model}}>
         {{#if this.editingTopic}}