DEV: lint & add tests for assigns_reminder_assigned_topics_query

Linted and added tests for `assigns_reminder_assigned_topics_query` modifier.

app/lib/plugin_initializer.rb

@@ -14,16 +14,15 @@ def apply_plugin_api
     end
   end
 
-  class AssignsRemainderForTopicsQuery < PluginInitializer
+  class AssignsReminderForTopicsQuery < PluginInitializer
     def apply_plugin_api
       plugin.register_modifier(:assigns_reminder_assigned_topics_query) do |query|
         next query if !SiteSetting.ignore_solved_topics_in_assigned_reminder
-        query.where(
-          "topics.id NOT IN (
-            SELECT topic_id
-            FROM topic_custom_fields
-            WHERE name = 'accepted_answer_post_id'
-          )",
+        query.where.not(
+          id:
+            TopicCustomField.where(
+              name: ::DiscourseSolved::ACCEPTED_ANSWER_POST_ID_CUSTOM_FIELD,
+            ).pluck(:topic_id),
         )
       end
     end

plugin.rb

@@ -47,6 +47,8 @@ class Engine < ::Rails::Engine
   require_relative "app/lib/web_hook_extension"
   require_relative "app/serializers/concerns/topic_answer_mixin"
 
+  require_relative "app/lib/plugin_initializer"
+  DiscourseSolved::AssignsReminderForTopicsQuery.new(self).apply_plugin_api
   module ::DiscourseSolved
     def self.accept_answer!(post, acting_user, topic: nil)
       topic ||= post.topic

spec/integration/solved_spec.rb

@@ -397,4 +397,30 @@
       expect(p1.topic.assignment.reload.status).to eq("Done")
     end
   end
+
+  context "with using assigns_reminder_assigned_topics_query modifier" do
+    class DummyClass
+      def test
+        DiscoursePluginRegistry.apply_modifier(:assigns_reminder_assigned_topics_query, Topic.all)
+      end
+    end
+
+    before { SiteSetting.ignore_solved_topics_in_assigned_reminder = true }
+
+    it "should not include solved topics in the query" do
+      topic = Fabricate(:topic)
+      topic2 = Fabricate(:topic)
+      topic3 = Fabricate(:topic)
+      post = Fabricate(:post, topic: topic)
+
+      DiscourseSolved.accept_answer!(post, Discourse.system_user)
+
+      topics = DummyClass.new.test.to_a
+
+      expect(topics).not_to include(topic)
+
+      expect(topics).to include(topic2)
+      expect(topics).to include(topic3)
+    end
+  end
 end