From e7a84948b970284a8a519a4329af17e2ce5a9bbe Mon Sep 17 00:00:00 2001
From: David Taylor <david@taylorhq.com>
Date: Wed, 24 Aug 2022 11:54:01 +0100
Subject: [PATCH] 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.
---
 .../discourse/app/adapters/topic-list.js      |  2 +-
 app/models/topic_list.rb                      | 12 +-----------
 spec/lib/topic_query_spec.rb                  |  2 +-
 spec/models/topic_list_spec.rb                | 19 ++-----------------
 spec/requests/categories_controller_spec.rb   |  2 +-
 5 files changed, 6 insertions(+), 31 deletions(-)

diff --git a/app/assets/javascripts/discourse/app/adapters/topic-list.js b/app/assets/javascripts/discourse/app/adapters/topic-list.js
index 34073796cd8..31fbd179ddf 100644
--- a/app/assets/javascripts/discourse/app/adapters/topic-list.js
+++ b/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;
diff --git a/app/models/topic_list.rb b/app/models/topic_list.rb
index 192687d1779..d13c2ab3ecd 100644
--- a/app/models/topic_list.rb
+++ b/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
diff --git a/spec/lib/topic_query_spec.rb b/spec/lib/topic_query_spec.rb
index b2183f2c980..7ff1fe9bd28 100644
--- a/spec/lib/topic_query_spec.rb
+++ b/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)
diff --git a/spec/models/topic_list_spec.rb b/spec/models/topic_list_spec.rb
index 89401996d18..f2ba6cfee19 100644
--- a/spec/models/topic_list_spec.rb
+++ b/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
diff --git a/spec/requests/categories_controller_spec.rb b/spec/requests/categories_controller_spec.rb
index c7dd184f741..5b927b7d99e 100644
--- a/spec/requests/categories_controller_spec.rb
+++ b/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