Fix editing issues and MRs with NULL lock_version

1 files changed, 41 insertions, 0 deletions

diff --git a/config/initializers/config_initializers_active_record_locking.rb b/config/initializers/config_initializers_active_record_locking.rb
new file mode 100644
index 00000000000..1c4352b135d
--- /dev/null
+++ b/config/initializers/config_initializers_active_record_locking.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+# rubocop:disable Lint/RescueException
+module ActiveRecord
+  module Locking
+    module Optimistic
+      private
+
+      def _update_row(attribute_names, attempted_action = "update")
+        return super unless locking_enabled?
+
+        begin
+          locking_column = self.class.locking_column
+          previous_lock_value = read_attribute_before_type_cast(locking_column)
+          attribute_names << locking_column
+
+          self[locking_column] += 1
+
+          # Patched because when `lock_version` is read as `0`, it may actually be `NULL` in the DB.
+          possible_previous_lock_value = previous_lock_value == 0 ? [nil, 0] : previous_lock_value
+
+          affected_rows = self.class.unscoped._update_record(
+            arel_attributes_with_values(attribute_names),
+            self.class.primary_key => id_in_database,
+            locking_column => possible_previous_lock_value
+          )
+
+          if affected_rows != 1
+            raise ActiveRecord::StaleObjectError.new(self, attempted_action)
+          end
+
+          affected_rows
+
+        # If something went wrong, revert the locking_column value.
+        rescue Exception
+          self[locking_column] = previous_lock_value.to_i
+          raise
+        end
+      end
+    end
+  end
+end