[transform-modules-umd] Better exported name for main module

[julien-f]

It would be nice if babel-plugin-transform-modules-umd would use the package name as exported name if the current file is main module of the package.

I would allow me to add this transform into all my modules and have them being usable in browsers (via unpkg.com for instance) without special config :)

[xtuc]

Could you please provide "Expected Behavior" and "Current Behavior" sections.

[julien-f]

Expected Behavior

The index.js module of my foo-bar package should be expose as global.fooBar.

Of course this is just an example because it should follow module resolution algorithm, such as the main entry in package.json

Current Behavior

The index.js module of my foo-bar package is exposed as global.index.

[xtuc]

We need a generic approach, which doesn't depend on a given directory structure.

One possible solution could be to expose an option to be able to custom the final module name and use #4630 (.babelrc.js) to resolve the package.json name.

[julien-f]

Hmm, I'm not sure it would be necessary, my use case is only for the entry point of the package.

[nicolo-ribaudo]

This can be easily done by using the moduleId option:

const path = require("path");

module.exports = {
  // Your normal config
  presets: [
    ["@babel/preset-env", { modules: "umd" }],
  ],

  overrides: [{
    // Only apply these options to the entry point
    include: path.resolve(__dirname, "src/index.js"),

    moduleId: require("./package.json").name,
    // If you prefer, you can specify the exact global identifier:
    moduleId: "myLibrary",
  }],
};

By doing so, Babel transforms don't have to understand node's resolution algorithm and it doesn't have to read non-babel options from package.json.

[julien-f]

@nicolo-ribaudo It was a long time ago so I don't remember my exact needs anymore but the whole point was to avoid specific configuration for each package.

Anyway, I don't have this need anymore so I won't reopen.