Refactor to handle the X-Cascade without having to raise an exception

actionpack/lib/action_dispatch/middleware/show_exceptions.rb

@@ -43,20 +43,20 @@ def initialize(app, consider_all_requests_local = false)
     end
 
     def call(env)
-      status, headers, body = @app.call(env)
-
-      # Only this middleware cares about RoutingError. So, let's just raise
-      # it here.
-      # TODO: refactor this middleware to handle the X-Cascade scenario without
-      # having to raise an exception.
-      if headers['X-Cascade'] == 'pass'
-        raise ActionController::RoutingError, "No route matches #{env['PATH_INFO'].inspect}"
+      begin
+        status, headers, body = @app.call(env)
+        exception = nil
+
+        # Only this middleware cares about RoutingError. So, let's just raise
+        # it here.
+        if headers['X-Cascade'] == 'pass'
+           exception = ActionController::RoutingError.new("No route matches #{env['PATH_INFO'].inspect}")
+        end
+      rescue Exception => exception
       end
-
-      [status, headers, body]
-    rescue Exception => exception
       raise exception if env['action_dispatch.show_exceptions'] == false
-      render_exception(env, exception)
+
+      exception ? render_exception(env, exception) : [status, headers, body]
     end
 
     private