FIX: Avoid duplicate topic-list requests (#18073)

When preloading topic_list data we were giving it a 'preload key' which was loosely based on the parameters of the list. However, it did not include all parameters, and mismatches between client/server-side logic would cause the preloaded data to be ignored.

This commit simplifies things by using a single key for all topic_list preloading. This works on the assumption that "The first topic_list the JS app will load is the one which was preloaded". That assumption also existed to some extent in the old design, so we don't expect any regressions here.

app/assets/javascripts/discourse/app/adapters/topic-list.js

@@ -32,7 +32,7 @@ export default RestAdapter.extend({
     const params = findArgs.params;
 
     return PreloadStore.getAndRemove(
-      "topic_list_" + filter,
+      "topic_list",
       finderFor(filter, params)
     ).then(function (result) {
       result.filter = filter;

app/models/topic_list.rb

@@ -76,17 +76,7 @@ class TopicList
   end
 
   def preload_key
-    if @category
-      if @opts[:no_subcategories]
-        "topic_list_#{@category.url.sub(/^\//, '')}/none/l/#{@filter}"
-      else
-        "topic_list_#{@category.url.sub(/^\//, '')}/l/#{@filter}"
-      end
-    elsif @tags && @tags.first.present?
-      "topic_list_tag/#{@tags.first.name}/l/#{@filter}"
-    else
-      "topic_list_#{@filter}"
-    end
+    "topic_list"
   end
 
   # Lazy initialization

spec/lib/topic_query_spec.rb

@@ -273,7 +273,7 @@ RSpec.describe TopicQuery do
 
       list = TopicQuery.new(moderator, category: diff_category.slug).list_latest
       expect(list.topics.size).to eq(1)
-      expect(list.preload_key).to eq("topic_list_c/different-category/#{diff_category.id}/l/latest")
+      expect(list.preload_key).to eq("topic_list")
 
       # Defaults to no category filter when slug does not exist
       expect(TopicQuery.new(moderator, category: 'made up slug').list_latest.topics.size).to eq(2)

spec/models/topic_list_spec.rb

@@ -97,24 +97,9 @@ RSpec.describe TopicList do
     let(:category) { Fabricate(:category) }
     let(:tag) { Fabricate(:tag) }
 
-    it "generates correct key for categories" do
+    it "returns topic_list" do
       topic_list = TopicList.new('latest', nil, nil, category: category, category_id: category.id)
-      expect(topic_list.preload_key).to eq("topic_list_c/#{category.slug}/#{category.id}/l/latest")
-    end
-
-    it "generates correct key for 'no subcategories' option" do
-      topic_list = TopicList.new('latest', nil, nil, category: category, category_id: category.id, no_subcategories: true)
-      expect(topic_list.preload_key).to eq("topic_list_c/#{category.slug}/#{category.id}/none/l/latest")
-    end
-
-    it "generates correct key for tag" do
-      topic_list = TopicList.new('latest', nil, nil, tags: [tag])
-      expect(topic_list.preload_key).to eq("topic_list_tag/#{tag.name}/l/latest")
-    end
-
-    it "generates correct key when both category and tags are missing" do
-      topic_list = TopicList.new('latest', nil, nil, tags: Tag.none)
-      expect(topic_list.preload_key).to eq("topic_list_latest")
+      expect(topic_list.preload_key).to eq("topic_list")
     end
   end
 end

spec/requests/categories_controller_spec.rb

@@ -21,7 +21,7 @@ RSpec.describe CategoriesController do
 
       expect(response.body).to have_tag("div#data-preloaded") do |element|
         json = JSON.parse(element.current_scope.attribute('data-preloaded').value)
-        expect(json['topic_list_latest']).to include(%{"more_topics_url":"/latest"})
+        expect(json['topic_list']).to include(%{"more_topics_url":"/latest"})
       end
     end