DEV: Fix `order:` filter not working on `/filter` route (#21330)

`TopicQuery#latest_results` which was being used by
`TopicQuery#list_filter` defaults to ordering by `Topic#bumped_at` in
descending order and that was taking precedent over the order scopes
being applied by `TopicsFilter`.

lib/topic_query.rb

@@ -270,7 +270,10 @@ class TopicQuery
 
   def list_filter
     topics_filter =
-      TopicsFilter.new(guardian: @guardian, scope: latest_results(include_muted: false))
+      TopicsFilter.new(
+        guardian: @guardian,
+        scope: latest_results(include_muted: false, skip_ordering: true),
+      )
 
     results = topics_filter.filter_from_query_string(@options[:q])
 
@@ -278,6 +281,8 @@ class TopicQuery
       results = remove_muted_topics(results, @user)
     end
 
+    results = apply_ordering(results) if results.order_values.empty?
+
     create_list(:filter, {}, results)
   end
 
@@ -618,7 +623,7 @@ class TopicQuery
     result.where("topics.category_id != ?", drafts_category_id)
   end
 
-  def apply_ordering(result, options)
+  def apply_ordering(result, options = {})
     sort_column = SORTABLE_MAPPING[options[:order]] || "default"
     sort_dir = (options[:ascending] == "true") ? "ASC" : "DESC"
 
@@ -732,7 +737,7 @@ class TopicQuery
       result = filter_by_tags(result)
     end
 
-    result = apply_ordering(result, options)
+    result = apply_ordering(result, options) if !options[:skip_ordering]
 
     all_listable_topics =
       @guardian.filter_allowed_categories(

spec/requests/list_controller_spec.rb

@@ -1308,6 +1308,36 @@ RSpec.describe ListController do
       end
     end
 
+    describe "when ordering using the `order:` filter" do
+      fab!(:topic2) { Fabricate(:topic, views: 2) }
+      fab!(:topic3) { Fabricate(:topic, views: 3) }
+      fab!(:topic4) { Fabricate(:topic, views: 1) }
+
+      it "return topics ordered by topic bumped at date in descending order when `q` query param is not present" do
+        sign_in(user)
+
+        get "/filter.json"
+
+        expect(response.status).to eq(200)
+
+        expect(response.parsed_body["topic_list"]["topics"].map { |topic| topic["id"] }).to eq(
+          [topic4.id, topic3.id, topic2.id, topic.id],
+        )
+      end
+
+      it "return topics ordered by views when `q` query param is `order:views`" do
+        sign_in(user)
+
+        get "/filter.json", params: { q: "order:views" }
+
+        expect(response.status).to eq(200)
+
+        expect(response.parsed_body["topic_list"]["topics"].map { |topic| topic["id"] }).to eq(
+          [topic3.id, topic2.id, topic4.id, topic.id],
+        )
+      end
+    end
+
     describe "when filtering by status" do
       fab!(:group) { Fabricate(:group) }
       fab!(:private_category) { Fabricate(:private_category, group: group) }