Refactor Status._insert_record slightly and tighten the test around reblogs of discarded statuses (#24516)

app/models/status.rb

@@ -391,9 +391,20 @@ class Status < ApplicationRecord
     super || build_status_stat
   end
 
-  # Hack to use a "INSERT INTO ... SELECT ..." query instead of "INSERT INTO ... VALUES ..." query
+  # This is a hack to ensure that no reblogs of discarded statuses are created,
+  # as this cannot be enforced through database constraints the same way we do
+  # for reblogs of deleted statuses.
+  #
+  # To achieve this, we redefine the internal method responsible for issuing
+  # the "INSERT" statement and replace the "INSERT INTO ... VALUES ..." query
+  # with an "INSERT INTO ... SELECT ..." query with a "WHERE deleted_at IS NULL"
+  # clause on the reblogged status to ensure consistency at the database level.
+  #
+  # Otherwise, the code is kept as close as possible to ActiveRecord::Persistence
+  # code, and actually calls it if we are not handling a reblog.
   def self._insert_record(values)
-    if values.is_a?(Hash) && values['reblog_of_id'].present?
+    return super unless values.is_a?(Hash) && values['reblog_of_id'].present?
+
     primary_key = self.primary_key
     primary_key_value = nil
 
@@ -415,9 +426,6 @@ class Status < ApplicationRecord
     raise ActiveRecord::InvalidForeignKey, "(reblog_of_id)=(#{values['reblog_of_id']}) is not present in table \"statuses\"" if result.nil?
 
     result
-    else
-      super
-    end
   end
 
   def self._compile_reblog_insert(values)

spec/services/reblog_service_spec.rb

@@ -38,7 +38,10 @@ RSpec.describe ReblogService, type: :service do
     let(:status) { Fabricate(:status, account: alice, visibility: :public) }
 
     before do
-      status.discard
+      # Update the in-database attribute without reflecting the change in
+      # the object. This cannot simulate all race conditions, but it is
+      # pretty close.
+      Status.where(id: status.id).update_all(deleted_at: Time.now.utc) # rubocop:disable Rails/SkipsModelValidations
     end
 
     it 'raises an exception' do