DEV: add support for adding custom status filter

Those can be used in the /filter routes.

lib/plugin/instance.rb

@@ -236,6 +236,14 @@ class Plugin::Instance
     DiscoursePluginRegistry.register_editable_group_custom_field(field, self)
   end
 
+  # Allows to define custom "status:" filter. Example usage:
+  #   register_custom_filter_by_status("foobar") do |scope|
+  #     scope.where("word_count = 42")
+  #   end
+  def register_custom_filter_by_status(status, &block)
+    TopicsFilter.add_filter_by_status(status, &block)
+  end
+
   # Allows to define custom search order. Example usage:
   #   Search.advanced_order(:chars) do |posts|
   #     posts.reorder("(SELECT LENGTH(raw) FROM posts WHERE posts.topic_id = subquery.topic_id) DESC")

lib/topics_filter.rb

@@ -86,6 +86,14 @@ class TopicsFilter
     @scope
   end
 
+  def self.add_filter_by_status(status, &blk)
+    (@custom_status_filters ||= {})[status] = blk
+  end
+
+  def self.custom_status_filters
+    @custom_status_filters || {}
+  end
+
   def filter_status(status:, category_id: nil)
     case status
     when "open"
@@ -106,6 +114,10 @@ class TopicsFilter
       end
     when "public"
       @scope = @scope.joins(:category).where("NOT categories.read_restricted")
+    else
+      if custom_filter = TopicsFilter.custom_status_filters[status]
+        @scope = custom_filter.call(@scope)
+      end
     end
 
     @scope

spec/lib/topics_filter_spec.rb

@@ -617,6 +617,18 @@ RSpec.describe TopicsFilter do
       fab!(:closed_topic) { Fabricate(:topic, closed: true) }
       fab!(:archived_topic) { Fabricate(:topic, archived: true) }
       fab!(:deleted_topic_id) { Fabricate(:topic, deleted_at: Time.zone.now).id }
+      fab!(:foobar_topic) { Fabricate(:topic, closed: true, word_count: 42) }
+
+      it "supports custom status filters" do
+        TopicsFilter.add_filter_by_status("foobar") { |scope| scope.where("word_count = 42") }
+
+        expect(
+          TopicsFilter
+            .new(guardian: Guardian.new)
+            .filter_from_query_string("status:foobar")
+            .pluck(:id),
+        ).to contain_exactly(foobar_topic.id)
+      end
 
       it "should only return topics that have not been closed or archived when query string is `status:open`" do
         expect(
@@ -642,7 +654,7 @@ RSpec.describe TopicsFilter do
             .new(guardian: Guardian.new)
             .filter_from_query_string("status:deleted")
             .pluck(:id),
-        ).to contain_exactly(topic.id, closed_topic.id, archived_topic.id)
+        ).to contain_exactly(topic.id, closed_topic.id, archived_topic.id, foobar_topic.id)
       end
 
       it "should only return topics that have been archived when query string is `status:archived`" do