If core-js version doesn't happen to resolve to 2, it produces a Babel error

[silvenon]

Environment

linaria@1.3.1
@babel/preset-env@7.5.5
@babel/cli@7.5.5

Description

Ok, this goes beyond my level of understanding, but let's try.

Linaria depends on core-js@^2.0.0, and the environment where Linaria is being used should also use core-js 2, but that resolution is not necessarily up to the linaria dependency. Linaria also depends on @babel/register^7.0.0, where @babel/register@7.0.0 (without the caret) depends on core-js 2, but @babel/register@7.4.0 depends on core-js 3. This usually doesn't seem to be a problem because in the real world other dependencies seem to ultimately depend on core-js 2, so that's what it resolves to, but Linaria shouldn't rely on that coincidence.

If I have the wrong version of core-js, I get the following Babel error:

{ Error: [BABEL] /Users/silvenon/Code/test/linaria/index.js: Cannot find module 'core-js/modules/es7.array.includes' (While processing: "/Users/silvenon/Code/test/linaria/node_modules/linaria/babel.js")
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:668:15)
    at Function.Module._load (internal/modules/cjs/loader.js:591:27)
    at Module.require (internal/modules/cjs/loader.js:723:19)
    at require (internal/modules/cjs/helpers.js:14:16)
    at Object.<anonymous> (/Users/silvenon/Code/test/linaria/node_modules/linaria/lib/babel/module.js:3:1)
    at Module._compile (internal/modules/cjs/loader.js:816:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:827:10)
    at Module.load (internal/modules/cjs/loader.js:685:32)
    at Function.Module._load (internal/modules/cjs/loader.js:620:12)
    at Module.require (internal/modules/cjs/loader.js:723:19) code: 'MODULE_NOT_FOUND' }

Reproducible Demo

Configure Babel:

// babel.config.js
module.exports = {
  presets: [
    'linaria/babel',
    '@babel/preset-react',
  ],
}

Create a Linaria class name:

// index.js
import { css } from 'linaria'

css`
  color: red;
`

Try to compile it with Babel:

yarn babel index.js

Solution

Temporary solution for people using Linaria:

yarn add core-js@^2

A permanent solution for Linaria might be locking @babel/register to 7.0.0, but I might be off about how module resolution works. 😄

[Daniel15]

Duplicate of #420 I think?

[lu-zen]

@silvenon since babel deprecated their polyfill pkg and recommended people to use core-js directly, I think lots of projects are going to depend on the latest version, which may be a problem since linaria has v2 as a dep =/

[silvenon]

I'm fine with whatever core-js version Linaria wants, this issue was about enforcing this, so the user knows what's going on, or preferably doesn't have to.