FIX: Exclude deleted posts and topics from assignments lists in various places (#34564)

This PR adds a check if the post an assignment is attached to is deleted
(by the author or another user) prior to listing it in
`/topics/group-topics-assigned/group_name.json`. This is done via
TopicQuery

Related:
https://meta.discourse.org/t/topic-deletion-should-clear-assignment/271996

plugins/discourse-assign/plugin.rb

@@ -376,18 +376,24 @@ after_initialize do
   add_to_class(:topic_query, :group_topics_assigned_results) do |group|
     list = default_results(include_all_pms: true)
 
-    topic_ids_sql = +<<~SQL
-      SELECT topic_id FROM assignments
-      WHERE (
-        assigned_to_id = :group_id AND assigned_to_type = 'Group' AND active
-      )
-    SQL
+    assignee_condition = "(a.assigned_to_id = :group_id AND a.assigned_to_type = 'Group')"
+    if @options[:filter] != :direct
+      assignee_condition +=
+        " OR (a.assigned_to_id IN (SELECT user_id from group_users where group_id = :group_id) AND a.assigned_to_type = 'User')"
+    end
 
-    topic_ids_sql << <<~SQL if @options[:filter] != :direct
-        OR (
-          assigned_to_id IN (SELECT user_id from group_users where group_id = :group_id) AND assigned_to_type = 'User' AND active
+    topic_ids_sql = <<~SQL
+      SELECT a.topic_id FROM assignments a
+      LEFT JOIN topics t ON t.id = a.topic_id
+      LEFT JOIN posts p ON p.id = a.target_id AND a.target_type = 'Post'
+      WHERE a.active
+        AND t.deleted_at IS NULL
+        AND (
+          a.target_type = 'Topic' OR
+          (a.target_type = 'Post' AND p.deleted_at IS NULL AND p.deleted_by_id IS NULL AND p.user_deleted = false)
         )
-      SQL
+        AND (#{assignee_condition})
+    SQL
 
     sql = "topics.id IN (#{topic_ids_sql})"
 

plugins/discourse-assign/spec/components/topic_query_spec.rb

@@ -103,6 +103,47 @@ describe TopicQuery do
 
       expect(assigned_messages).to contain_exactly(group_topic)
     end
+
+    it "excludes assignments to deleted posts and topics" do
+      # Create a new topic with only a post assignment (no topic assignment)
+      post_only_topic = Fabricate(:post, user: user).topic
+      post_in_topic = Fabricate(:post, topic: post_only_topic)
+      assign_to(post_in_topic, user, user)
+
+      assigned_messages =
+        TopicQuery.new(user, { page: 0 }).list_group_topics_assigned(assign_allowed_group).topics
+      expect(assigned_messages).to contain_exactly(
+        private_message,
+        topic,
+        group_topic,
+        post_only_topic,
+      )
+
+      # delete entire topic (soft deletion)
+      post_only_topic.update!(deleted_at: Time.current)
+      assigned_messages =
+        TopicQuery.new(user, { page: 0 }).list_group_topics_assigned(assign_allowed_group).topics
+      expect(assigned_messages).to contain_exactly(private_message, topic, group_topic)
+
+      # restore topic, but delete the post (moderator deletion)
+      post_only_topic.update!(deleted_at: nil)
+      post_in_topic.update!(deleted_at: Time.current)
+      assigned_messages =
+        TopicQuery.new(user, { page: 0 }).list_group_topics_assigned(assign_allowed_group).topics
+      expect(assigned_messages).to contain_exactly(private_message, topic, group_topic)
+
+      # user deletion of post
+      post_in_topic.update!(deleted_at: nil, user_deleted: true)
+      assigned_messages =
+        TopicQuery.new(user, { page: 0 }).list_group_topics_assigned(assign_allowed_group).topics
+      expect(assigned_messages).to contain_exactly(private_message, topic, group_topic)
+
+      # system deletion of post
+      post_in_topic.update!(user_deleted: false, deleted_by_id: Discourse.system_user.id)
+      assigned_messages =
+        TopicQuery.new(user, { page: 0 }).list_group_topics_assigned(assign_allowed_group).topics
+      expect(assigned_messages).to contain_exactly(private_message, topic, group_topic)
+    end
   end
 
   describe "#list_private_messages_assigned" do