Babel/ES2015 Support

[bcoe]

with the --babel flag, nyc is the easiest way to add ES2015 support to your project:

1. install the appropriate babel dependencies for your project (npm i babel-core babel-preset-es2015 --save).
2. create a .babelrc file:

{
  "presets": ["es2015"]
}

1. install nyc, and run it with the --babel flag:

nyc --babel mocha

nyc uses source-maps to map coverage information back to the appropriate lines of the pre-transpiled code:

This is a pretty big change, and I would love some help with the code review, you can try it out in your project by running:

npm i nyc@alpha --save-dev

I hope it solves the problems folks were having with nyc + babel:

CC: @Janpot, @shannonmoeller, @lfilho, @sindresorhus

[shannonmoeller]

Fantastic! Thanks!

[sindresorhus]

// @jamestalmage @vdemedes

[jamestalmage]

// @novemberborn

[shannonmoeller]

Couple things:

1. I had to add babel-polyfill to my test.js file. Is that expected?
2. nyc's version of Istanbul is out-of-date. I manually bumped it to 0.4.1 and it worked out-of-the-box.

[bcoe]

@shannonmoeller is babel-polyfill an alternative to using .babelrc with an appropriate preset? I think that this is how babel recommends doing things now?

Things worked well otherwise? You'd be happy to see this land?

[shannonmoeller]

Ah. It's because I'm using async/await in my test file.

I'd absolutely love to see this land. Once ava supports Babel 6, I can switch from blue-tape and enter node testing nirvana.

Thanks for your work on this! 👏

[bcoe]

@shannonmoeller do you think that nyc should make an attempt to require babel-polyfill? If this is a dependency in the package.json, is it a general rule that we will always want to include it?

[shannonmoeller]

As long as it's clearly documented as a feature of the --babel flag, I think that would be okay. Depends on how many assumptions you're comfortable making.

What about having a --require config/flag similar to mocha's?

// package.json
{
  "config": {
    "nyc": {
      "require": ["babel-polyfill"]
    }
}

[bcoe]

@shannonmoeller I like this concept for the API much better than having a --babel flag \o/

see: 1735bfd

And let me know if this does the trick for you:

nyc --require babel-polyfill --require babel-core/register

[shannonmoeller]

Now that's beautiful. This is working perfectly for me:

{
  "name": "foo",
  "version": "1.0.0",
  "main": "src/index.js",
  "scripts": {
    "coveralls": "nyc report -r text-lcov | coveralls",
    "test": "nyc -r html -r text blue-tape test/*.js",
    "watch": "watch 'npm run test' src test -d"
  },
  "devDependencies": {
    "babel-polyfill": "^6.2.0",
    "babel-preset-es2015": "^6.1.18",
    "babel-preset-stage-0": "^6.1.18",
    "babel-register": "^6.2.0",
    "blue-tape": "^0.1.11",
    "coveralls": "^2.11.4",
    "nyc": "git+https://github.com/bcoe/nyc.git#1735bfdc",
    "watch": "^0.16.0"
  },
  "config": {
    "nyc": {
      "require": [
        "babel-register",
        "babel-polyfill"
      ]
    }
  }
}

[shannonmoeller]

I really like how this change makes this a bring-your-own-transpiler coverage tool. Should work just as easily with coffeescript and typescript now.

[Janpot]

@bcoe Yes, this:

nyc -r babel-core/register npm test !

👍

[joews]

I get SyntaxError: Unexpected token import running $ npm test with package.json:

{
  "scripts": {
    "test": "nyc tape \"./test/**/*.js\" | faucet",
  },
  "config": {
    "nyc": {
      "require": [
        "babel-register",
        "babel-polyfill"
      ]
    }
  },
  "devDependencies": {
    "babel-cli": "^6.2.0",
    "babel-core": "^6.2.1",
    "babel-preset-es2015": "^6.1.18",
    "faucet": "0.0.1",
    "istanbul": "^0.3.17",
    "lodash": "^3.10.0",
    "nyc": "git+ssh://[email protected]:bcoe/nyc.git#babel",
    "pegjs": "^0.8.0",
    "sql.js": "^0.2.21",
    "tape": "^4.0.1"
  }
}

babel-runtime seems to be required because I need regeneratorRuntime.

With this setup, however, $ npm run coverage works as expected.

"scripts": {
    "test": "babel-node $( which tape) \"./test/**/*.js\" | faucet",
    "coverage": "nyc npm test --reporter lcov",
  }

Can you see what I'm doing wrong in the former case?

[bcoe]

@jwhitfieldseed is the code your instrumenting open-source, mind linking me to the project and I'll take a look?

@Janpot did you give that a shot with a couple of your projects? I'd like to publish this pretty soon 👍

[joews]

@bcoe nvm, rm -rf node_modules && npm i did the trick 😄

👍 for config.nyc.require in package.json.

[joews]

@bcoe actually, scratch that. This setup works with [email protected], fails with [email protected] (after rm -rf node_modules && npm install && npm test):

https://github.com/jwhitfieldseed/prequel/blob/master/package.json
https://travis-ci.org/jwhitfieldseed/prequel

Error with node 4.1.1:

(function (exports, require, module, __filename, __dirname) { import test from "tape";
                                                              ^^^^^^
SyntaxError: Unexpected reserved word
...

[shannonmoeller]

@jwhitefieldseed Looks like you need to npm i -D babel-register babel-polyfill

Edit: Corrected typo in install command.

[joews]

@shannonmoeller That didn't fix it, I'm afraid.

At first thought it was a problem with Babel 6 config rather than nyc interop, but, on Node 4, this npm test script works:

"babel-node $(which tape) \"./test/**/*.js\" | faucet"

And this fails immediately with the above SyntaxError:

"nyc tape \"./test/**/*.js\" | faucet && nyc report --reporter text",

Both work on Node 5.

[joews]

@shannonmoeller Ah - babel-register, not babel-require. Should have realised that! Problem solved, sorry about the noise. nyc with Babel is looking excellent 👍

[shannonmoeller]

Yep! Sorry about the typo.

[bcoe]

@shannonmoeller @jwhitfieldseed, given that you now explicitly specify a list of libraries to require, perhaps I should stop using try-require and let it simply throw? I think this would have helped bring out this typo sooner?

[shannonmoeller]

@bcoe Sounds good to me.

[joews]

@bcoe 👍 I would have caught the difference between Node 4 and Node 5 (or as I now realise, npm 2 vs npm 3) immediately with an early Cannot find module 'babel-register'.

[bcoe]

@mindmelting just published a hot-fix of nyc, [email protected] which should solve this problem for you.

Let me know if it does the trick?