From f753643cb10d7eeacc49ba204b95caa6edaa1a8b Mon Sep 17 00:00:00 2001
From: Martin Brennan <martin@discourse.org>
Date: Fri, 1 Nov 2019 09:19:43 +1000
Subject: [PATCH] FIX: Unread topics not clearing when whisper is last post
 (#8271)

Meta thread: https://meta.discourse.org/t/cant-dismiss-unread-if-last-post-is-an-assign-or-whisper/131823/7

* when sending a whisper, the highest_staff_post_number is set
in the next_post_number method for a Topic, but the
highest_post_number is left alone. this leaves a situation
where highest_staff_post_number is > highest_post_number
* when TopicsBulkAction#dismiss_posts was run, it was only setting the topic_user
highest_seen_post_number using the highest_post_number from the topic, so if
the user was staff and the last post in a topic was a whisper
their highest seen number was not set, and the topic stayed unread

Found through testing that the bug wasn't to do with Assign/Unassign as they do not affect the post numbers, only whispering does.
---
 lib/topics_bulk_action.rb                  |  3 ++-
 spec/components/topics_bulk_action_spec.rb | 26 ++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/lib/topics_bulk_action.rb b/lib/topics_bulk_action.rb
index a26dc0eb0a..5c45a01c9b 100644
--- a/lib/topics_bulk_action.rb
+++ b/lib/topics_bulk_action.rb
@@ -68,9 +68,10 @@ class TopicsBulkAction
   end
 
   def dismiss_posts
+    highest_number_source_column = @user.staff? ? 'highest_staff_post_number' : 'highest_post_number'
     sql = <<~SQL
       UPDATE topic_users tu
-      SET highest_seen_post_number = t.highest_post_number , last_read_post_number = highest_post_number
+      SET highest_seen_post_number = t.#{highest_number_source_column} , last_read_post_number = t.#{highest_number_source_column}
       FROM topics t
       WHERE t.id = tu.topic_id AND tu.user_id = :user_id AND t.id IN (:topic_ids)
     SQL
diff --git a/spec/components/topics_bulk_action_spec.rb b/spec/components/topics_bulk_action_spec.rb
index b0788c8b78..58cc96283c 100644
--- a/spec/components/topics_bulk_action_spec.rb
+++ b/spec/components/topics_bulk_action_spec.rb
@@ -20,6 +20,32 @@ describe TopicsBulkAction do
       expect(tu.last_read_post_number).to eq(3)
       expect(tu.highest_seen_post_number).to eq(3)
     end
+
+    context "when the user is staff" do
+      fab!(:user) { Fabricate(:admin) }
+
+      context "when the highest_staff_post_number is > highest_post_number for a topic (e.g. whisper is last post)" do
+        it "dismisses posts" do
+          post1 = create_post(user: user)
+          p = create_post(topic_id: post1.topic_id)
+          create_post(topic_id: post1.topic_id)
+
+          whisper = PostCreator.new(
+            user,
+            topic_id: post1.topic.id,
+            post_type: Post.types[:whisper],
+            raw: 'this is a whispered reply'
+          ).create
+
+          TopicsBulkAction.new(user, [post1.topic_id], type: 'dismiss_posts').perform!
+
+          tu = TopicUser.find_by(user_id: user.id, topic_id: post1.topic_id)
+
+          expect(tu.last_read_post_number).to eq(4)
+          expect(tu.highest_seen_post_number).to eq(4)
+        end
+      end
+    end
   end
 
   describe "invalid operation" do