watch usage unclear or broken

[tcurdt]

This works:

$ sass -v
Sass 3.4.20 (Selective Steve)
$ sass index.scss index.css

Watching does not:

$ sass -h
    --watch                      Watch files or directories for changes.
                                 The location of the generated CSS can be set using a colon:
                                   sass --watch input.sass:output.css

$ sass --watch index.scss:index.css
>>> Sass is watching for changes. Press Ctrl-C to stop.
I, [2016-01-06T18:21:57.699128 #61495]  INFO -- : Celluloid 0.17.2 is running in BACKPORTED mode. [ http://git.io/vJf3J ]
ArgumentError: wrong number of arguments (2 for 1)
Use --trace for backtrace.

Here is the backtrace:

/Users/user/.gem/ruby/2.2.3/gems/celluloid-0.17.2/lib/celluloid/calls.rb:48:in `check': wrong number of arguments (2 for 1) (ArgumentError)
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-0.17.2/lib/celluloid/calls.rb:26:in `dispatch'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-0.17.2/lib/celluloid/call/sync.rb:16:in `dispatch'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-0.17.2/lib/celluloid/cell.rb:50:in `block in dispatch'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-0.17.2/lib/celluloid/cell.rb:76:in `block in task'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-0.17.2/lib/celluloid/actor.rb:339:in `block in task'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-0.17.2/lib/celluloid/task.rb:44:in `block in initialize'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-0.17.2/lib/celluloid/task/fibered.rb:14:in `block in create'
  from (celluloid):0:in `remote procedure call'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-0.17.2/lib/celluloid/call/sync.rb:45:in `value'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-0.17.2/lib/celluloid/proxy/sync.rb:38:in `method_missing'
  from /Users/user/.gem/ruby/2.2.3/gems/listen-2.7.12/lib/listen/listener.rb:206:in `_init_actors'
  from /Users/user/.gem/ruby/2.2.3/gems/listen-2.7.12/lib/listen/listener.rb:87:in `block in <class:Listener>'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-fsm-0.20.5/lib/celluloid/fsm.rb:176:in `instance_eval'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-fsm-0.20.5/lib/celluloid/fsm.rb:176:in `call'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-fsm-0.20.5/lib/celluloid/fsm.rb:129:in `transition_with_callbacks!'
  from /Users/user/.gem/ruby/2.2.3/gems/celluloid-fsm-0.20.5/lib/celluloid/fsm.rb:97:in `transition'
  from /Users/user/.gem/ruby/2.2.3/gems/listen-2.7.12/lib/listen/listener.rb:100:in `start'
  from /Users/user/.gem/ruby/2.2.3/gems/sass-3.4.20/lib/sass/plugin/compiler.rb:402:in `block in listen_to'
  from /Users/user/.gem/ruby/2.2.3/gems/sass-3.4.20/lib/sass/plugin/compiler.rb:402:in `map'
  from /Users/user/.gem/ruby/2.2.3/gems/sass-3.4.20/lib/sass/plugin/compiler.rb:402:in `listen_to'
  from /Users/user/.gem/ruby/2.2.3/gems/sass-3.4.20/lib/sass/plugin/compiler.rb:338:in `watch'
  from /Users/user/.gem/ruby/2.2.3/gems/sass-3.4.20/lib/sass/plugin.rb:108:in `method_missing'
  from /Users/user/.gem/ruby/2.2.3/gems/sass-3.4.20/lib/sass/exec/sass_scss.rb:381:in `watch_or_update'
  from /Users/user/.gem/ruby/2.2.3/gems/sass-3.4.20/lib/sass/exec/sass_scss.rb:51:in `process_result'
  from /Users/user/.gem/ruby/2.2.3/gems/sass-3.4.20/lib/sass/exec/base.rb:52:in `parse'
  from /Users/user/.gem/ruby/2.2.3/gems/sass-3.4.20/lib/sass/exec/base.rb:19:in `parse!'
  from /Users/user/.gem/ruby/2.2.3/gems/sass-3.4.20/bin/sass:13:in `<top (required)>'
  from /Users/user/.gem/ruby/2.2.3/bin/sass:23:in `load'
  from /Users/user/.gem/ruby/2.2.3/bin/sass:23:in `<main>'

[chriseppstein]

Please update your listen gem. Using version 2.10.1 it works fine.

[tcurdt]

@chriseppstein not here

$ gem install listen
Successfully installed listen-3.0.5
1 gem installed
$ sass --watch index.scss:index.css
>>> Sass is watching for changes. Press Ctrl-C to stop.
I, [2016-01-06T21:50:26.011129 #61745]  INFO -- : Celluloid 0.17.2 is running in BACKPORTED mode. [ http://git.io/vJf3J ]
ArgumentError: wrong number of arguments (2 for 1)
  Use --trace for backtrace.

[tcurdt]

Does it require a listen 2.x then?

[tcurdt]

Hm. I had a version 2.7.x - that didn't work. 3.x doesn't work either. 2.10.1 is rather old - what am I missing?

[tcurdt]

This is what I was missing https://github.com/sass/sass/tree/stable/vendor
Removing the installed (and newer) gem versions let it fall back to the vendored version.
Wow - that sucks. But at least it works now.

[chriseppstein]

We will happily support as many versions of the listen gem as we can, I was trying to give you a work around in the short term. Please file a new issue with steps to reproduce the issue with a particular version of listen.

[tcurdt]

@chriseppstein looks like all from 2.7.x on upwords should be broken
Just installing the latest listen gem should be enough to reproduce it.

Maybe the easier way would be to have sass really be a script that calls bundle exec? Obviously there are many incompatibilities between the listen versions. So supporting all does not really sound like the best path forward.

[chriseppstein]

If people are using bundler then they should call bundle exec sass.

We don't have a hard dependency on listen because there are lots of dependencies in the newer versions and we don't want people to have to install those especially since they are not necessarily using the command line.

Ideally, we'd break the CLI into it's own gem with it's own dependencies and keep it separate from the core compiler. Then we'd make the cli gem have a strong dependency on the listen gem and things would Just Work™.

[tcurdt]

bundle exec sass does not really work for CLI commands out of the box. Bundler needs to find the Gemfile. You would have to wrap it in shell script to make it convenient. And you also don't want to leave users with dependency hell by not using bundler either.

Bundler or not - the CLI gem path certainly is a good idea.