Fix thread depth computation in statuses_controller (#9426)

* Add test that should currently fail

* Fix depth computation (will still fail if statuses have been filtered out)

* Fix handling of broken threads

1 files changed, 13 insertions, 11 deletions

diff --git a/app/controllers/statuses_controller.rb b/app/controllers/statuses_controller.rb
index 0f3fe198f..15d59fd89 100644
--- a/app/controllers/statuses_controller.rb
+++ b/app/controllers/statuses_controller.rb
@@ -65,12 +65,13 @@ class StatusesController < ApplicationController
 
   private
 
-  def create_descendant_thread(depth, statuses)
+  def create_descendant_thread(starting_depth, statuses)
+    depth = starting_depth + statuses.size
     if depth < DESCENDANTS_DEPTH_LIMIT
-      { statuses: statuses }
+      { statuses: statuses, starting_depth: starting_depth }
     else
       next_status = statuses.pop
-      { statuses: statuses, next_status: next_status }
+      { statuses: statuses, starting_depth: starting_depth, next_status: next_status }
     end
   end
 
@@ -101,16 +102,19 @@ class StatusesController < ApplicationController
     @descendant_threads = []
 
     if descendants.present?
-      statuses = [descendants.first]
-      depth    = 1
+      statuses       = [descendants.first]
+      starting_depth = 0
 
       descendants.drop(1).each_with_index do |descendant, index|
         if descendants[index].id == descendant.in_reply_to_id
-          depth += 1
           statuses << descendant
         else
-          @descendant_threads << create_descendant_thread(depth, statuses)
+          @descendant_threads << create_descendant_thread(starting_depth, statuses)
 
+          # The thread is broken, assume it's a reply to the root status
+          starting_depth = 0
+
+          # ... unless we can find its ancestor in one of the already-processed threads
           @descendant_threads.reverse_each do |descendant_thread|
             statuses = descendant_thread[:statuses]
 
@@ -119,18 +123,16 @@ class StatusesController < ApplicationController
             end
 
             if index.present?
-              depth += index - statuses.size
+              starting_depth = descendant_thread[:starting_depth] + index + 1
               break
             end
-
-            depth -= statuses.size
           end
 
           statuses = [descendant]
         end
       end
 
-      @descendant_threads << create_descendant_thread(depth, statuses)
+      @descendant_threads << create_descendant_thread(starting_depth, statuses)
     end
 
     @max_descendant_thread_id = @descendant_threads.pop[:statuses].first.id if descendants.size >= DESCENDANTS_LIMIT