Generator class throws an error in development build

[robertedjones]

Is this a bug report?

Yes

Did you try recovering your dependencies?

1.6.0

Which terms did you search for in User Guide?

Babel, Generator Functions

Environment

1. node -v: 8.11.1
2. npm -v: 5.6.0
3. yarn --version (if you use Yarn): 1.6.0
4. npm ls react-scripts (if you haven’t ejected): react-scripts@2.0.0-next.66cc7a90

Then, specify:

1. Operating system: Windows 10
2. Browser and version (if relevant): Chrome 65.0.3325.181, Firefox Quantum 59.0.2 (64-bit)

Steps to Reproduce

During a development build Babel does not correctly convert generator functions in a class. The exact issue I am experiencing is described in this issue facebook/regenerator#287 but that appears to have since been resolved. This issue only occurs in a development build and works correctly during a production build. It was working correctly in react-scripts 1.x. - react-scripts@2.0.0-next.66cc7a90 is the first 2.x build I have tried. This may be a Babel issue rather than a CRA issue.

1. Create a generator class

export default class GeneratorClass {
  *getReply(msg) {
    yield msg;
  }
}

2. Invoke the classs

const reply = new Reply();
var r = reply.getReply('Hello ');
console.log('gen', r.next());

3. yarn start
4. ReferenceError: _callee is not defined

Expected Behavior

Babel correctly transpiles generator functions in a class and no error is given

Actual Behavior

The error:

ReferenceError: _callee is not defined

Reproducible Demo

https://github.com/robertedjones/my-app

[SenyaMur]

Add to package.json
"react-app-rewired": "^1.5.2"
Update "react-scripts" to "2.0.0-next.3e165448"
Update babel dependencies in package.json

    "@babel/core": "^7.0.0-rc.1",
    "@babel/plugin-proposal-class-properties": "^7.0.0-rc.1",
    "@babel/plugin-proposal-object-rest-spread": "^7.0.0-rc.1",
    "@babel/plugin-syntax-dynamic-import": "^7.0.0-rc.1",
    "@babel/plugin-transform-classes": "^7.0.0-rc.1",
    "@babel/plugin-transform-destructuring": "^7.0.0-rc.1",
    "@babel/plugin-transform-react-constant-elements": "^7.0.0-rc.1",
    "@babel/plugin-transform-react-display-name": "^7.0.0-rc.1",
    "@babel/plugin-transform-regenerator": "^7.0.0-rc.1",
    "@babel/plugin-transform-runtime": "^7.0.0-rc.1",
    "@babel/preset-env": "^7.0.0-rc.1",
    "@babel/preset-react": "^7.0.0-rc.1",
    "@babel/runtime": "^7.0.0-rc.1"

Add config-overrides.js for enable use .babelrc

module.exports = {
    webpack: function(config, env) {
      const oneOf =config.module.rules.find(i=> i.oneOf).oneOf
      oneOf[1].use[1].options.babelrc= true;  
      return config;
    }
  };

.babelrc

{
  "presets": [
    ["@babel/preset-env", {
      "targets": {
        "browsers": ["last 2 versions", "safari >= 7"]
      },
      "include": ["transform-arrow-functions", "es6.map"],
      "exclude": ["transform-regenerator", "es6.set"]
    }]
  ]
}

[Timer]

This should be fixed with #4630