Allow to disable regenerator-runtime

With the current configuration, async is transpiled into generators. If I have an error in an async function, my VS Code with chrome-debugger extension loads bundle.js and jumps to _asyncToGenerator ... catch (error) { reject(error); return; } ... there which is quite laggy.

Exception has occurred: Error
Error
    at _callee3$ (/Users/anton/Work/abc/src/containers/src.js:125:1)
    at tryCatch (/Users/anton/Work/abc/node_modules/regenerator-runtime/runtime.js:62:1)
    at Generator.invoke [as _invoke] (/Users/anton/Work/campaign-design/node_modules/regenerator-runtime/runtime.js:296:1)
    at Generator.prototype.(anonymous function) [as next] (/Users/anton/Work/abc/node_modules/regenerator-runtime/runtime.js:114:1)
    at step (http://localhost:3000/static/js/bundle.js:93038:191)
    at http://localhost:3000/static/js/bundle.js:93038:361
    at <anonymous>

Since async/await is widely supported, and during development, it’s desirable to disable the regenrator runtime.

For anyone interested, you have to update node_modules/babel-preset-react-app/index.js and add

        exclude: [
            'transform-regenerator',
            'transform-async-to-generator',
          ],

at line 113 (babel-preset-env config), then do yarn --force.

This also means I can’t set brakepoints at the lines with await keyword which is pretty annoying.

[z-vr]

I think I can do

"browserslist": {
  "development": [
    "last 1 Chrome version"
  ]
}

actually thanks.

[justingrant]

@mrapogee - Unfortunately the ability to use browsersList to disable regenerator and other polyfills was removed before V2 of CRA was released. Like you, I also wasted a bunch of time before figuring it out that the advice given by @Timer and @z-vr was accurate when they gave it, but it doesn’t apply anymore to current CRA2 releases.

If you (like me!) want to see this implemented, @ianschmitz suggested to make #6198 the master issue to track this request. Go there add your votes and ideas!