FEATURE: Add `solved_topics_auto_close_hours` site setting.

https://meta.discourse.org/t/automatically-close-solved-topics-after-n-hours/58383

config/locales/server.en.yml

@@ -5,6 +5,7 @@ en:
     accept_all_solutions_trust_level: "Minimum trust level required to accept solutions on any topic (even when not OP)"
     empty_box_on_unsolved: "Display an empty box next to unsolved topics"
     solved_quote_length: "Number of characters to quote when displaying the solution under the first post"
+    solved_topics_auto_close_hours: "Auto close topic (n) hours after the last reply once the topic has been marked as solved"
   reports:
     accepted_solutions:
       title: "Accepted solutions"

config/settings.yml

@@ -14,4 +14,5 @@ plugins:
   solved_quote_length:
     default: 300
     client: false
-
+  solved_topics_auto_close_hours:
+    default: 0

plugin.rb

@@ -65,10 +65,11 @@ SQL
       limit_accepts
 
       post = Post.find(params[:id].to_i)
+      topic = post.topic
 
-      guardian.ensure_can_accept_answer!(post.topic)
+      guardian.ensure_can_accept_answer!(topic)
 
-      accepted_id = post.topic.custom_fields["accepted_answer_post_id"].to_i
+      accepted_id = topic.custom_fields["accepted_answer_post_id"].to_i
       if accepted_id > 0
         if p2 = Post.find_by(id: accepted_id)
           p2.custom_fields["is_accepted_answer"] = nil
@@ -81,8 +82,8 @@ SQL
       end
 
       post.custom_fields["is_accepted_answer"] = "true"
-      post.topic.custom_fields["accepted_answer_post_id"] = post.id
-      post.topic.save!
+      topic.custom_fields["accepted_answer_post_id"] = post.id
+      topic.save!
       post.save!
 
       if defined?(UserAction::SOLVED)
@@ -102,13 +103,22 @@ SQL
                            data: {
                              message: 'solved.accepted_notification',
                              display_username: current_user.username,
-                             topic_title: post.topic.title
+                             topic_title: topic.title
                            }.to_json
                           )
       end
 
-      DiscourseEvent.trigger(:accepted_solution, post)
+      if (auto_close_hours = SiteSetting.solved_topics_auto_close_hours) > 0
+        topic.set_or_create_timer(
+          TopicTimer.types[:close],
+          auto_close_hours,
+          based_on_last_post: true
+        )
 
+        MessageBus.publish("/topic/#{topic.id}", reload_topic: true)
+      end
+
+      DiscourseEvent.trigger(:accepted_solution, post)
       render json: success_json
     end
 
@@ -236,7 +246,7 @@ SQL
                  .joins(:user)
                  .pluck('post_number', 'username', 'cooked')
                  .first
-      
+
       if postInfo
         postInfo[2] = PrettyText.excerpt(postInfo[2], SiteSetting.solved_quote_length)
         return postInfo

spec/integration/solved_spec.rb

@@ -0,0 +1,31 @@
+require 'rails_helper'
+
+RSpec.describe "Managing Posts solved status" do
+  let(:topic) { Fabricate(:topic) }
+  let(:user) { Fabricate(:trust_level_4) }
+  let(:p1) { Fabricate(:post, topic: topic) }
+
+  before do
+    SiteSetting.allow_solved_on_all_topics = true
+  end
+
+  describe 'accepting a post as the answer' do
+    before do
+      sign_in(user)
+      SiteSetting.solved_topics_auto_close_hours = 2
+    end
+
+    it 'can mark a post as the accepted answer correctly' do
+      xhr :post, "/solution/accept", id: p1.id
+
+      expect(p1.reload.custom_fields["is_accepted_answer"]).to eq("true")
+
+      expect(topic.public_topic_timer.status_type).to eq(TopicTimer.types[:close])
+
+      expect(topic.public_topic_timer.execute_at)
+        .to be_within(1.second).of(Time.zone.now + 2.hours)
+
+      expect(topic.public_topic_timer.based_on_last_post).to eq(true)
+    end
+  end
+end