Babel: root programmatic options

Question

I seem to absolutely not grasp where to put root programmatic options for the babel.

If I have a monorepo and need to tell the different sub packages that they shall look upwards for my babel.config.js then I should put rootMode: "upwards" into the .babelrc of the sub packages, correct? This does not work, because of the resulting error

Error: .rootMode is only allowed in root programmatic options

Somehow I simply can't find any example of where to put/use root programmatic options... Can anyone point me to the right direction?

Answer 1

If you are using Webpack, you need to put it there.

module: {
  [..]
  rules: [
    // Transpile ES6 Javascript into ES5 with babel loader
    {
      test: /\.jsx?$/,
      exclude: [/node_modules/, /json/],
      loader: 'babel-loader',
      options: {
        rootMode: 'upward'
      },
    },
    [..]
  ],
  [..]
},

Otherwise I had the same issue than you, I can't put it in the package.json file using the key babel.

Answer 2

Any API-related options are called programmatic options. Take a look at my discussion with the primary maintainer of Babel: https://github.com/babel/babel/discussions/14405.

It's when you specify them directly to Babel (babel.transformSync(code, programmaticOptions) or to the Babel integration you are using (e.g. babel-loader, which can pass them to its internal babel.transform call). In other words, not in presets or config files. [...]

by @nicolo-ribaudo - Babel core team.