Build action_cable.js with Blade

[javan]

• Compiles action_cable.js with Blade, which essentially uses the same Sprockets setup we had in the rake task. No need to duplicate.
• Uses sprocket-export's #= export directive to replace the somewhat incomplete implementation

/cc @maclover7 @jeremy

[matthewd]

Does this make blade a runtime requirement for anyone running out of a git clone?

[javan]

No. Unknown Sprockets directives are ignored so without Blade the default behavior applies (setting window.ActionCable).

[javan]

I updated Blade to output the build process and handle cleaning the dist path:

$ bundle exec rake assets:compile
Building assets…
[removed] lib/assets/compiled/action_cable.js
[created] lib/assets/compiled/action_cable.js

[vipulnsward]

@javan I see some downgrades, are they intentional from blade? or the dropping of coffee-script versions, etc.

[javan]

These dependencies were all added recently in 61483b1 when Blade 0.5.1 was introduced. It turns out Thin (a dependency of Blade) doesn't work with event machine 1.2.0 so I backed away from it in javan/blade@62c8cb0. Blade also removed exact dependencies on coffee-script and sprockets to reduce conflicts with apps that have tighter requirements. So if we want specific versions, we should declare them.

[rafaelfranca]

Backported in 45083d8

[javan]

Thanks, @rafaelfranca! Is it possible to release actioncable-5.0.1 independently (to fix #25649) or are the Rails gems always released together?

[rafaelfranca]

They are always released together. If you see the rails.gemspec we ask for the same version of the subgems. https://github.com/rails/rails/blob/master/rails.gemspec#L28.

If it is a critical fix we can do a full release early, but this is more something to @matthewd decide since he is the release manager of the next release.

[javan]

Cool. I don't think it's critical.