With format: iife, support exports as globals

[edwinm]

Feature Use Case

I have a source file with an export:

export function a() {…}

I also have a rollup.config.js which has two outputs:

  output: [
    {
      file: "dist/bundle.min.js",
      format: "es",
      name: "bundle",
      sourcemap: true,
    },
    {
      file: "dist/bundle.iife.min.js",
      format: "iife",
      name: "b",
      sourcemap: true,
    },
  ],

Using the es version, I can use import {a} from 'bundle';, this works fine.

Using the iife version, I can only access a as b.a, which is undesirable.

Feature Proposal

I propose a solution to address this and make it possible to have a available as a global variable instead of a property of the bundle.

This feature has been requested in #494, but the (hacky) solution doesn't work anymore.

Possible solutions to indicate this in the config are:

1. Just omit output.name.
2. Set output.name to the empty string ""
3. Set output.name to "window", similar to the solution in issue export to multiple globals without moduleName (IIFE)  #494.

[janpaepke]

I stumbled across this issue, when I wanted to use named exports for my bundle but directly attach them to the window for iife.
I only have one export from my entry, but for UMD and ESM I still prefer it be named, which is why I am not using default exports.
To quote your example I want window.a, rather than window.b.a.

I am currently using the hacky solution from #494 (using name: 'window' and extend: true), which produces exactly the desired output.
However it comes with a caveat: It also adds __esModule: true to window, which probably makes limited sense.
I am hesitant to set output.esModule to false as I am unsure of the implications.

Regarding your proposals I would also disagree with the proposed config.
Setting it to nothing or "" would prevent rollup from warning about accidental settings (which it currently does and I think is sensible).
Setting it to window is, as I think we all agree, a bit hacky.
Also none of your options would allow you to export a as window.b, which is what I would expect from your config.

I think the most sensible option would be to allow it to work similar to output.globals.
This means you can either pass in an object or a function to define the renames.

Applying this to your config:

  output: [
    {
      file: "dist/bundle.iife.min.js",
      format: "iife",
      name: {
        "a": "b"
      },
      sourcemap: true,
    },
  ],

Would make a available as window.b.

What do you think?