Unsure how usage-pure and transform-runtime should work

[jquense]

Sorry for the slew of issues, we are really testing out the work here (it's awesome!). The docs suggest that this can be used instead of corejs specific runtime packages:

{
  "presets": [
    ["@babel/preset-env", {
      "targets": { "firefox": 42 }
    }]
  ],
  "plugins": [
    ["@babel/transform-runtime", {
      "corejs": 3
    }]
  ]
}

It's unclear to me though how this would work for helpers that also need polyfills. like AsyncGenerator. Is this case supposed to be covered?

[nicolo-ribaudo]

When designing these plugins, I decided to threat @babel/runtime as a normal dependency: you compile it if you need. Note that this wasn't possible in the past and caused recursion errors in the compiled output, but it's safe since Babel 7.8.4 it is safe.

I would thus configure Babel like this:

// babel.config.json
{
  "overrides": [{
    "test": "./src",
    "presets": [
      ["@babel/preset-env", {
        "targets": { "firefox": 42 }
      }]
    ],
    "plugins": [
      "@babel/transform-runtime"
    ]
  }, {
    "test": ["./src", "./node_modules/@babel/runtime"],
    "plugins": [
      ["polyfill-corejs3", {
        "method": "usage-pure",
        "targets": { "firefox": 42 }
      }]
    ]
  }]
}

[nicolo-ribaudo]

Demo: https://github.com/nicolo-ribaudo/repro-babel-polyfills-32 (npm ci and ./node_modules/.bin/webpack)

[jquense]

sweet, makes sense 👍