Task assets:clean is executed without checking whether it exists

[j15e]

Context

Using Rails 6 without Sprocket, with Webpacker only.

What happen

This exception happen after assets compilation :

   Done in 5.16s.
   Asset precompilation completed (64.17s)
   Cleaning assets
   Running: rake assets:clean
   I, [2019-11-25T17:07:47.298404 #605]  INFO -- sentry: ** [Raven] Sending event 5db44a5151c44a8a8699a7ccaa2edf71 to Sentry
   rake aborted!
   Don't know how to build task 'assets:clean' (See the list of available tasks with `rake --tasks`)
   /tmp/build_400672b08b175a998e4d7f78b88ee830/vendor/bundle/ruby/2.6.0/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
   (See full trace by running task with --trace)

Why

The task assets:precompile is defined when using webpacker or sprocket, but the assets:clean is not defined when using only webpacker.

The rails buidpack check the assets:precompile exist before calling it :

heroku-buildpack-ruby/lib/language_pack/rails4.rb

Lines 84 to 85 in 1a30c5a

	precompile = rake.task("assets:precompile")
	return true unless precompile.is_defined?

So I think a simple fix could be to check wether the assets:clean exist too before calling it :

heroku-buildpack-ruby/lib/language_pack/rails4.rb

Lines 98 to 99 in 1a30c5a

	puts "Cleaning assets"
	rake.task("assets:clean").invoke(env: rake_env)

And /or check also for webpacker:clean task and invoke that one when required.

What do you think?

Other stuff I found :

• Webpacker "enhance" the assets:clean task, but only if it exist because sprocket is also used (https://github.com/rails/webpacker/pull/1744/files)
• Related PR Rails 5.1 Webpacker Cache Support #892

[SampsonCrowley]

this is a major issue, how is there not a single reply yet?

[schneems]

this is a major issue, how is there not a single reply yet?

I missed the original issue when it came in. I can queue this up. It's an easy fix