Rails hooking a custom generator into scaffold generator

In a new Rails 6.1.3 project, I'm attempting to have bin/rails generate scaffold Thing name:string invoke the typical Rails scaffolding (including active_record and scaffold_controller) as well as invoking my own custom generator to create an additional ThingForm that I want to be a part of my scaffolding.

I created a custom generator for form that works just fine by itself. bin/rails generate form Thing name:string is properly setting up an app/forms/thing_form.rb.

But in attempting to get this generator hooked into the default scaffolding generator, I'm running into different problems with different approaches I've tried.

1. Inspired by active_model_serializers, when I set up a hook_for :form as part of Rails::Generators::ResourceGenerator it ends up no longer invoking active_record. Here's the commit from my example repo: https://github.com/diachini/generator_hook_investigation/commit/8989b8f96b05ac1157d1d3a247bee9f0f2befe5d

   • To confirm I wasn't crazy, I have another branch that just confirmed generating a scaffold with active_model_serializers installed properly keeps the active_record invocation happening.

2. Taking a page out of this Gist explaining custom generators - I similarly attempted a hook_foron the ScaffoldGenerator and the ControllerGenerator

   • Just like my active_model_serializers attempt, this no longer invoked active_record.
   • It also began ignoring config for turning off assets and scaffold_stylesheet.
   • On a separate branch in my example repo: https://github.com/diachini/generator_hook_investigation/commit/86bc7b53ac34ea29d5e32d07486c73d962f86247

3. I saw a similar StackOverflow question with an update regarding copying the whole ScaffoldGenerator, but was hoping to avoid that approach if there's something simple that I'm missing with the hook_for approach that active_model_serializers took.