Babel 7 support

[laurentpayot]

Babel 7 is out!

For transpilation CoffeeScript still looks for a babel-core package instead of the new Babel 7 @babel/core.
More details: http://babeljs.io/blog/2017/12/27/nearing-the-7.0-release#renames-scoped-packages-babel-x

• CoffeeScript version: 2.3.1
• Node.js version: 10.8.0

[bazineta]

So far as I can see, the new version seems to work fine with CS 2.3.1. In a Unix environment, you can do a

ln -s @babel/core babel-core

in your node_modules directory if you'd like to do a quick sanity check with the new babel-core version.

[GeoffreyBooth]

This is probably as easy as updating

coffeescript/src/index.coffee

Lines 10 to 12 in 7f8b36a

	try
	babel = require 'babel-core'
	catch

to also try to require @babel/core. We should keep the check for babel-core as well, for users who haven’t upgraded to Babel 7 yet. CoffeeScript might as well work with both 6 and 7 if they’re both compatible.

Anyone up for an easy PR?

[bazineta]

@GeoffreyBooth There are three files affected; index.coffee, repl.coffee, and command.coffee.

The changes are all straightforward, seemingly along the lines of:

 try
    babel = require '@babel/core'
  catch
    try
      babel = require 'babel-core'
    catch
      # This error is only for Node, as CLI users will see a different error
      # earlier if they don’t have Babel installed.
      throw new Error 'To use the transpile option, you must have the \'@babel/core\' or \'babel-core\' module installed'

Though it gets quite duplicative and therefore might be something that should have a common function for, especially given the nested try blocks. However, it's indeed a quick and easy change to all 3, though I'm not sure what the tests would be, other than 'does not explode in flames', I suppose.

[bazineta]

@GeoffreyBooth PR #5102, though as mentioned, an appropriate test other than does not go bang is unclear to me at present.

[GeoffreyBooth]

Any tests that the old version had would apply to the new one. Though I’m not sure if we wrote tests for the transpile option; we probably should if we haven’t.

I guess if you wanted to abstract this, you could make a getBabel function that returns the babel object, or throws. Then the original locations could be rewritten like:

 try 
   babel = getBabel()
 catch

And you could put the double-try stuff inside getBabel.

[bazineta]

I think that upon further consideration, this is probably not something that'll need to be dual-pathed for an extended period of time, as those who use Babel are, frankly, likely to upgrade quickly, at least in my opinion.

[laurentpayot]

@bazineta thanks for the PR. I'm using the symbolic link workaround (in postinstall script) for months now, as Babel 7 has been in beta/RC for a long time. Babel users also didn't wait for the official v7 release to use it. So I guess it is safe now for CS to use Babel 7.

[Inve1951]

I don't see the need to break old setups.

those who use Babel are, frankly, likely to upgrade quickly

The transpile option is ment for ppl who really don't use babel.

[laurentpayot]

The transpile option is ment for ppl who really don't use babel.

I use Babel a lot, via babel-loader in Webpack. Still I have to run scripts in CS with the transpile option…

[bazineta]

I use Babel a lot, via babel-loader in Webpack

Same here; that's our use of it, via webpack loaders. The PR supports both pre-7 and 7+ babel.

[loganfsmyth]

I'll note that, in the short term anyway, users can probably install babel-core@7.0.0-bridge.0, which is a package that just redirects to @babel/core.

[GeoffreyBooth]

Done in #5105.

[max-degterev]

@GeoffreyBooth could we get a quick bump to 2.3.2 to have this fix available in npm?

[GeoffreyBooth]

Please see #5110. Anyone available to review that?

[laurentpayot]

Thanks everyone 👍