Allow app to opt out of precompiling activestorage js assets

[jlestavel]

Summary

Since PR #42895, Active Storage adds 2 JS assets to precompile:

rails/activestorage/lib/active_storage/engine.rb

Lines 169 to 173 in a8d088f

	initializer "active_storage.asset" do
	if Rails.application.config.respond_to?(:assets)
	Rails.application.config.assets.precompile += %w( activestorage activestorage.esm )
	end
	end

It's currently not possible to opt out. Our app does not use this Active Storage JS and it causes some issues with Sprockets and Uglifier. It would be helpful if we could disable this assets addition in the config.

Other Information

Action Cable has the same behavior of adding assets to precompile (introduced in #42856), but as you can see below it can be disabled:

rails/actioncable/lib/action_cable/engine.rb

Lines 26 to 32 in a8d088f

	initializer "action_cable.asset" do
	config.after_initialize do |app|
	if Rails.application.config.respond_to?(:assets) && app.config.action_cable.precompile_assets
	Rails.application.config.assets.precompile += %w( actioncable.js actioncable.esm.js )
	end
	end
	end

Specifically, this opt-out option was introduced by DHH in 3fd4185 so basically I mimicked this commit.

[jlestavel]

@dhh I am taking the liberty of pinging you, as you're the one who introduced those new assets (and also the one who added the optout option for Action Cable ones). And @rafaelfranca because you were tagged in 3fd4185 (which is basically the same as this PR) so I guess you may be interested by this one

[ghiculescu]

It looks good. Could you rebase?

[jlestavel]

It looks good. Could you rebase?

Done ✔️

[ghiculescu]

Sorry, could you also squash to a single commit? (https://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html#squashing-commits)

[jlestavel]

Sorry, could you also squash to a single commit?

Done ✔️

[jlestavel]

@ghiculescu is there anything missing to approve this PR ?

[ghiculescu]

It just needs review from the core team :)

[jlestavel]

Ok thanks for your answer. No need to add them as reviewers ?

For people who would look for a temporary fix, here's what we added in our config/application.rb to remove the 2 JS assets:

initializer "active_storage.remove_assets", after: "active_storage.asset" do |app|
  app.config.assets.precompile -= %w[activestorage activestorage.esm]
end

[dhh]

Can't we just refer to app.config here, rather than the two Rails.application.config?

[jlestavel]

✔️ right, that's done.

I wrote it like this to be consistent with what you did in 3fd4185 but it's better like that. For consistency again, I changed the code in Action Cable too.

[dhh]

Looking good. I know it's a little awkward with tests for this. So just want to confirm that you've verified this working in your local app?

[jlestavel]

Yes, I tested it locally using

gem 'rails', '~> 7.0', github: 'wecasa/rails', branch: 'activestorage_assets_precompile_optout'

in my Gemfile. And I could be able to use this new config.active_storage.precompile_assets option