FIX: Serialize categories for group posts (#26663)

This is necessary when "lazy load categories" feature is enabled to
make sure the categories are rendered for group posts.

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

@@ -8,6 +8,7 @@ import { ajax } from "discourse/lib/ajax";
 import Category from "discourse/models/category";
 import GroupHistory from "discourse/models/group-history";
 import RestModel from "discourse/models/rest";
+import Site from "discourse/models/site";
 import Topic from "discourse/models/topic";
 import User from "discourse/models/user";
 import discourseComputed from "discourse-common/utils/decorators";
@@ -463,15 +464,16 @@ export default class Group extends RestModel {
       data.category_id = parseInt(opts.categoryId, 10);
     }
 
-    const posts = await ajax(`/groups/${this.name}/${type}.json`, { data });
+    const result = await ajax(`/groups/${this.name}/${type}.json`, { data });
-    const categories = await Category.asyncFindByIds(
-      posts.map((p) => p.category_id)
-    );
 
-    return posts.map((p) => {
+    result.categories?.forEach((category) => {
+      Site.current().updateCategory(category);
+    });
+
+    return result.posts.map((p) => {
       p.user = User.create(p.user);
       p.topic = Topic.create(p.topic);
-      p.category = categories[p.category_id];
+      p.category = Category.findById(p.category_id);
       return EmberObject.create(p);
     });
   }

app/controllers/groups_controller.rb

@@ -196,7 +196,16 @@ class GroupsController < ApplicationController
 
     posts =
       group.posts_for(guardian, params.permit(:before_post_id, :before, :category_id)).limit(20)
-    render_serialized posts.to_a, GroupPostSerializer
+
+    response = { posts: serialize_data(posts, GroupPostSerializer) }
+
+    if guardian.can_lazy_load_categories?
+      category_ids = posts.map { |p| p.topic.category_id }.compact.uniq
+      categories = Category.secured(guardian).with_parents(category_ids)
+      response[:categories] = serialize_data(categories, CategoryBadgeSerializer)
+    end
+
+    render json: response
   end
 
   def posts_feed

spec/requests/groups_controller_spec.rb

@@ -551,7 +551,7 @@ RSpec.describe GroupsController do
       get "/groups/#{group.name}/posts.json"
 
       expect(response.status).to eq(200)
-      expect(response.parsed_body.first["id"]).to eq(post.id)
+      expect(response.parsed_body["posts"].first["id"]).to eq(post.id)
     end
 
     it "returns moderator actions" do
@@ -560,7 +560,7 @@ RSpec.describe GroupsController do
       get "/groups/#{group.name}/posts.json"
 
       expect(response.status).to eq(200)
-      expect(response.parsed_body.first["id"]).to eq(post.id)
+      expect(response.parsed_body["posts"].first["id"]).to eq(post.id)
     end
   end