FIX: topic link reflections deleted on second save

app/models/topic_link.rb

@@ -178,6 +178,16 @@ class TopicLink < ActiveRecord::Base
               prefix = Discourse.base_url_no_prefix
 
               reflected_url = "#{prefix}#{post.topic.relative_url(post.post_number)}"
+
+              tl = TopicLink.find_by(topic_id: topic_id,
+                                     post_id: reflected_post.try(:id),
+                                     url: reflected_url)
+
+              if tl
+                tl.update_columns(domain: Discourse.current_hostname,
+                                  link_topic_id: post.topic.id,
+                                  link_post_id: post.id)
+              else
                 tl = TopicLink.create(user_id: post.user_id,
                                     topic_id: topic_id,
                                     post_id: reflected_post.try(:id),
@@ -188,6 +198,8 @@ class TopicLink < ActiveRecord::Base
                                     link_topic_id: post.topic_id,
                                     link_post_id: post.id)
 
+              end
+
               reflected_ids << tl.try(:id)
             end
           end

spec/models/topic_link_spec.rb

@@ -92,6 +92,10 @@ http://b.com/#{'a'*500}
         topic.posts.create(user: user, raw: 'initial post')
         linked_post = topic.posts.create(user: user, raw: "Link to another topic: #{url}")
 
+        # this is subtle, but we had a bug were second time
+        # TopicLink.extract_from was called a reflection was nuked
+        2.times do
+          topic.reload
           TopicLink.extract_from(linked_post)
 
           link = topic.topic_links.first
@@ -113,6 +117,7 @@ http://b.com/#{'a'*500}
           expect(reflection.link_post_id).to eq(linked_post.id)
 
           expect(reflection.user_id).to eq(link.user_id)
+        end
 
         linked_post.revise(post.user, { raw: "no more linkies https://eviltrout.com" })
         expect(other_topic.topic_links.where(link_post_id: linked_post.id)).to be_blank