Babel-cli: allow to install globally, with ability to invoke local babel

[Strate]

As many nodejs-related tools, it would be good to allow global babel-cli installation, which will invoke local (related to process.cwd()) babel installation.

EDIT by @hzoo

• Comment below you are going to do this (for others to know)
• Read CONTRIBUTING.md
• Join our slack if you haven't already if you need more immediate help or just comment in this issue/PR
• Check out ava's implementation that @sindresorhus linked: https://github.com/avajs/ava/blob/ad5122d507bfaa044fc3a2e51e467238e16dba11/cli.js#L7-L16, https://github.com/broccolijs/broccoli-cli does something similar
• modify our babel-cli: https://github.com/babel/babel/tree/master/packages/babel-cli
  • https://github.com/babel/babel/blob/master/packages/babel-cli/bin/babel.js, https://github.com/babel/babel/blob/master/packages/babel-cli/src/babel/index.js
• a manual test
• possibly a unit test (we can help)

[babel-bot]

Hey @Strate! We really appreciate you taking the time to report an issue. The collaborators
on this project attempt to help as many people as possible, but we're a limited number of volunteers,
so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack
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[sindresorhus]

👍 Feel free to borrow our implementation of this in @avajs: https://github.com/avajs/ava/blob/ad5122d507bfaa044fc3a2e51e467238e16dba11/cli.js#L7-L16

[varemenos]

I'd like to work on this

[varemenos]

I've got a couple of questions about this feature's implementation.

1. Should we inform the user every time they invoke a local copy of babel? (Will they get confused if we don't? Will they get annoyed if we do this every single time?)

2. Should the babel-cli try to resolve the ./node_modules/babel-core based only on the cwd or should it try to find the closest parent's directory that contains a package.json based on the cwd and then try to resolve the path ./node_modules/babel-core?

Before merging: We should update this part of the documentation website

Note: Since it's generally a bad idea to run Babel globally you may want to uninstall the global copy by running npm uninstall --global babel-cli.

https://github.com/babel/babel.github.io/blob/27a5d2c894af56ad49e8504b6ada2d1739fba829/_includes/tools/babel_cli/install.md

[sindresorhus]

Should the babel-cli try to resolve the ./node_modules/babel-core based on the cwd only or should it try to find the closest package.json based on the cwd and then try to resolve the path ./node_modules/babel-core?

Should walk up. That's how require works and would IMHO be the expected behavior.

[loganfsmyth]

Is the proposal here that this call a local babel-core or a local babel-cli? I don't think I'd want it to have any knowledge of babel-core at all, since then we're way more likely to run into versioning mismatches, whereas if it proxies through to a local babel-cli things will likely work alright.

Should we inform the user every time they invoke a local copy of babel?

I'd be in favor of printing a message, we'll just have to make sure that we disable the message when Babel is set up to output transpiled output to stdout or else the message would corrupt the output JS.

[sindresorhus]

Call the local babel-cli.

[varemenos]

Sorry for the delay with this issue, I've had some personal issue the past few days.
Yep, as it seems, I've misunderstood the purpose of the issue. Ok so, I'll replace the invocation of babel-core to babel-cli and add log a message when babel's is not set up to output transpiled output to stdout.

Are there any conflicts between this issue and #5258?

[loganfsmyth]

I don't think there are any conflicts, I wouldn't worry about it.