@vue/babel-preset-app option exclude conflict

[ac88]

Version

3.12.1

Reproduction link

https://github.com/vuejs/vue-cli/blob/dev/packages/%40vue/babel-preset-app/index.js#L8

Environment info

Chrome: 82

Steps to reproduce

at babel.config.js config exclude:['es6.promise']

What is expected?

build dist code exclude core-js es6.promise

What is actually happening?

only set exclude:['es6.promise'] then build dist code still include core-js es6.promise

---

require config polyfills:['es6.array.iterator','es6.object.assign'] rewrite defaultPolyfills

but node_modules/@babel/preset-env/lib/built-in-definitions.js has Promise definitions

const definitions = {
  builtins: {
    //...
    Map: ["es6.map"].concat(CommonIterators),
    Number: "es6.number.constructor",
    Promise: ["es6.object.to-string", "es6.promise"]
    //...
  }
}

may be defaultPolyfills can remove es6.promise

[lovetingyuan]

es6.promise is always included, see https://cli.vuejs.org/guide/browser-compatibility.html#polyfills

Note that es6.promise is included by default because it's very common for libs to depend on Promises.

[lucaswerkmeister]

We also have a use case for this feature request. We don’t mind Promise being polyfilled, whether other libs require it or not; however, Promise is already polyfilled on the page where our app is used, and so it’s unnecessary to include a Promise polyfill in our app bundle, and we would like to remove it to save some bytes (core-js’ Promise polyfill is rather weighty). I’ll send a pull request.

[lovetingyuan]

Most modern browsers already support Promise for a long time, so the polyfill for Promise should not be compulsory any more.