DEV: Support `status:public` in topics filtering query language (#20889)

This commit adds support for the `status:public` filter which only
return topics that belong to public categories.

lib/topics_filter.rb

@@ -51,6 +51,8 @@ class TopicsFilter
       if @guardian.can_see_deleted_topics?(category)
         @scope = @scope.unscope(where: :deleted_at).where("topics.deleted_at IS NOT NULL")
       end
+    when "public"
+      @scope = @scope.joins(:category).where("NOT categories.read_restricted")
     end
 
     @scope

spec/lib/topics_filter_spec.rb

@@ -2,6 +2,7 @@
 
 RSpec.describe TopicsFilter do
   fab!(:admin) { Fabricate(:admin) }
+  fab!(:group) { Fabricate(:group) }
 
   describe "#filter_from_query_string" do
     describe "when filtering with multiple filters" do
@@ -87,6 +88,22 @@ RSpec.describe TopicsFilter do
             .pluck(:id),
         ).to contain_exactly(topic.id)
       end
+
+      it "should only return topics that are not in any read-restricted category when query string is `status:public`" do
+        private_category = Fabricate(:private_category, group: group)
+        topic_in_private_category = Fabricate(:topic, category: private_category)
+
+        expect(
+          TopicsFilter.new(guardian: Guardian.new).filter_from_query_string("").pluck(:id),
+        ).to include(topic_in_private_category.id)
+
+        expect(
+          TopicsFilter
+            .new(guardian: Guardian.new)
+            .filter_from_query_string("status:public")
+            .pluck(:id),
+        ).not_to include(topic_in_private_category.id)
+      end
     end
 
     describe "when filtering by tags" do

spec/requests/list_controller_spec.rb

@@ -1179,5 +1179,25 @@ RSpec.describe ListController do
         expect(parsed["topic_list"]["topics"].first["id"]).to eq(topic_with_tag.id)
       end
     end
+
+    describe "when filtering by status" do
+      fab!(:group) { Fabricate(:group) }
+      fab!(:private_category) { Fabricate(:private_category, group: group) }
+      fab!(:topic_in_private_category) { Fabricate(:topic, category: private_category) }
+
+      it "does not return topics from read restricted categories when `q` query param is `status:public`" do
+        group.add(user)
+
+        sign_in(user)
+
+        get "/filter.json?q=status:public"
+
+        expect(response.status).to eq(200)
+
+        expect(
+          response.parsed_body["topic_list"]["topics"].map { |topic| topic["id"] },
+        ).to contain_exactly(topic.id, topic_with_tag.id, topic2_with_tag.id)
+      end
+    end
   end
 end