'export default from' can not be correctly compiled

[leaves4j]

Choose one: bug

Input Code

var from = 'test';
export default from;

Babel/Babylon Configuration (.babelrc, package.json, cli command)

{
  presets: [
        [
          '@babel/preset-env', {
            targets: { browsers: ['android>=4', 'ios>=7'] },
            modules: false,
          },
        ],
      ],
      plugins: [
        '@babel/plugin-transform-runtime',
      ],
}

Expected Behavior

Compiled correctly

Current Behavior

Throw an error

[!] (babel plugin) SyntaxError: /xxx/node_modules/@babel/runtime/core-js/array/from.js: Support for the experimental syntax 'exportDefaultFrom' isn't currently enabled (6:8):

  4 | var from = require$$0;
  5 |
> 6 | export default from;
    |        ^
  7 | export { from as __moduleExports };

Add @babel/plugin-proposal-export-default-from (https://git.io/vb4yH) to the 'plugins' section of your Babel config to enable transformation.

software	version(s)
Babel	7.0.0-beta.38
Babylon
node	9.4
npm
Operating System	mac os

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[nveenjain]

I think that's a bug in babylon. I'll look into it.

export default from;

This code should throw an Reference error as from is not defined (take it as separate example from your code), but rather it asks for additional(experimental) plugin to be added, which in turns does not accept this code either. Will try to solve and open a PR asap..

[nveenjain]

@KFlash , i think this line is causing the error in babylon as this line in isExportDefaultSpecifier function does not consider the possibility that from might be lineTerminator..

[nveenjain]

@KFlash , exactly, i was going to do the same.. I didn't know how V8, Esprima or SM implement it though. Thanks for the feedback..

[nveenjain]

@KFlash , i've submitted a PR, would really appreciate review.

[vzaidman]

also on 7.0.0 it seems like there is no way to make the following work:

export x from './y'

[FraBle]

@vzaidman did you find a solution?

[vzaidman]

i did many things and cant recall which of them helped.

make sure to use @babel/plugin-proposal-export-namespace-from.
make sure to upgrade babel-loader

sorry - no better advice

[johanazhu]

https://babeljs.io/docs/en/babel-plugin-proposal-export-default-from

[alex-cory]

@vzaidman do you think you could maybe post a snippet of your babel setup so we can see what presets/plugins you used and what babel dependencies you have to make everything work? Been stuck on this one for a little bit. I know order matters with some so that would also be helpful to see

[vzaidman]

not sure it's the best possible but still:
babel.config.js:

module.exports = function (api) {
  api.cache(true)

  return {
    presets: [
      ['@babel/preset-env', {
        useBuiltIns: 'entry',
        loose: true
      }],
      '@babel/preset-react'
    ],
    plugins: [
      '@babel/plugin-proposal-export-default-from',
      '@babel/plugin-proposal-export-namespace-from',
      '@babel/plugin-proposal-object-rest-spread',
      ['@babel/plugin-proposal-decorators', {legacy:true}],
      ['@babel/plugin-proposal-class-properties', {loose: true}]
    ]
  }
}

notice we use decorators so plugin-proposal-class-properties must be loose.

[helloanoop]

Adding the plugins '@babel/plugin-proposal-export-namespace-from' and '@babel/plugin-proposal-export-default-from' worked for me.