Use the most highest priority exception handler when cause is set

There was some subtle breakage caused by #18774, when we removed
`#original_exception` in favor of `#cause`. However, `#cause` is
automatically set by Ruby when raising an exception from a rescue block.
With this change, we will use whichever handler has the highest priority
(whichever call to `rescue_from` came last). In cases where the outer
has lower precidence than the cause, but the outer is what should be
handled, cause will need to be explicitly unset.

Fixes #23925

1 files changed, 10 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/rescuable.rb b/activesupport/lib/active_support/rescuable.rb
index fcf5553061..73bc52b56f 100644
--- a/activesupport/lib/active_support/rescuable.rb
+++ b/activesupport/lib/active_support/rescuable.rb
@@ -115,5 +115,15 @@ module ActiveSupport
         end
       end
     end
+
+    def index_of_handler_for_rescue(exception)
+      handlers = self.class.rescue_handlers.reverse_each.with_index
+      _, index = handlers.detect do |(klass_name, _), _|
+        klass = self.class.const_get(klass_name) rescue nil
+        klass ||= (klass_name.constantize rescue nil)
+        klass === exception if klass
+      end
+      index
+    end
   end
 end