Traceur not working with Jest. Unable to use ES6.

[licx]

My codebase is written in ES6 so I tried to set-up Traceur as scriptPreprocessor

Package.json

"jest": {
    "scriptPreprocessor": "<rootDir>/preprocessor.js"
}

preprocessor.js

var traceur = require('traceur');
module.exports = {
  process: function(src, path) {
    var result = traceur.compile(src);
    return result;
  }
};

When I try to run my tests with npm test I always get:

[Error: Malformed child response message: {}]

[JogoShugh]

Any luck on this?

[hysios]

package.json

"jest":  {
    "setupEnvScriptFile": "<rootDir>/node_modules/traceur/bin/traceur-runtime.js",
}

preprocessor.js

var traceur = require('traceur');
module.exports = {
  process: function(src, path) {
    if (path.indexOf('node_modules') === -1) {
      src = traceur.compile(src);
    }
    return src;
 }
};

You can try add above code to test.

[dmaj7no5th]

No luck doing the same. When I try to run the traceur compiler in a preprocess function, I get the following error:

Variable 'require' has already been declared
node_modules/traceur/bin/traceur.js:22696

[dmaj7no5th]

I'm trying to combine React + ES6 with Jest, and can't get beyond the following:

// in package.json
  "jest": {
    "setupEnvScriptFile": "node_modules/traceur/bin/traceur-runtime.js",
    "scriptPreprocessor": "jest.conf.js",
    "unmockedModulePathPatterns": [
      "node_modules/react"
    ]
  }

// jest.conf.js
var ReactTools = require('react-tools'),
    traceur = require('traceur');
module.exports = {
    process: function (src, path) {
        if (path.indexOf('node_modules') === -1) {
            src = traceur.compile(
                ReactTools.transform(src),
                { experimental: true }
            );
        }
        return src;
    }
};

When I try to run the tests, I get the following error:

Found 1 matching test...
/Users/pperry/example/node_modules/traceur/bin/traceur.js:22696 

  var require = function(id) { 
      ^^^^^^^ 
 FAIL  app/js/models/__tests__/example-class-test.js 

SyntaxError: /Users/pperry/example/jest.conf.js: Variable 'require' has already been declared

The module I'm trying to test exports an ES6 class (it has no imports). The test just tries to create an instance of the class and verify a property on it. No matter how I wire it, when I get Traceur involved, I hit this error.

[jamiebuilds]

Hey guys, contributor to 6to5 here. I'm not sure how to get traceur working, but 6to5 has an official jest plugin to make it easier. It also plays well with react/jsx if you're using those. If you need any help let me know or feel free to stop by our gitter room.

[randylien]

If you are working with React, react-tools supports ES6 transform.

var ReactTools = require('react-tools');
module.exports = {
    process: function(src) {
        return ReactTools.transform(src, {
            harmony: true
        });
    }
};

[jamiebuilds]

@randylien You can get much more ES6 support in addition to full React/JSX support in 6to5. http://6to5.org/docs/usage/jsx/

[leebyron]

It may be failing if you're not also including the Traceur runtime.

Your transform should also concat the traceur runtime to the top of the file.

I have no idea where the error about defining require is coming from. That seems like a bad idea on Traceur's part if they're doing that.

[licx]

Looks like this is how you can use ES6 with React

package.son

  "dependencies": {
    "react": "*",
    "react-tools": "*"
  },
  "jest": {
    "scriptPreprocessor": "<rootDir>/preprocessor.js",
    "unmockedModulePathPatterns": ["<rootDir>/node_modules/react"]
  }

preprocessor.js

var ReactTools = require('react-tools');
module.exports = {
    process: function(src) {
        return ReactTools.transform(src, {
            harmony: true
        });
    }
};

It's basically the same procedure shown here http://facebook.github.io/jest/docs/tutorial-react.html#content with the addition of the harmony flag to the ReactTools.transform call.

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