creating `OptionManager` instances is super slow in @babel/register

[Swatinem]

Bug Report

Current Behavior

The first thing @babel/register does is create a new OptionManager:

babel/packages/babel-register/src/node.js

Line 41 in f2af6c1

const opts = new OptionManager().init(

It does that for all files, even things that I want to explicitly ignore, such as node_modules.
Even though I use the option babelrc: false, which should tell it to not resolve .babelrc files via the filesystem.

For a quite large app we have, creating these OptionManager instances alone accounts for ~20 seconds of our app startup, which would normally start in ~4 seconds with precompiled code, without the register hook.

Expected behavior/code

Things should be fast. :-)

Babel Configuration (.babelrc, package.json, cli command)

register({
  babelrc: false,
  extensions: ['.js', '.ts', '.tsx'],
    ignore: [/node_modules/, /dist/, /\.d\.ts$/],
    sourceMaps: 'both',
    presets: [
      [
        '@babel/preset-env',
        {
          shippedProposals: true,
          targets: { node: true },
          modules: 'commonjs',
          useBuiltIns: 'entry',
        },
      ],
      '@babel/preset-react',
      '@babel/preset-typescript',
      '@babel/preset-flow',
    ],
    plugins: ['@babel/plugin-proposal-class-properties', '@babel/plugin-syntax-dynamic-import', 'dynamic-import-node'],
})

Environment

• Babel version(s): 7.2.2
• Node/npm version: node 8
• OS: linux
• Monorepo: yes, lerna
• How you are using Babel: register

Possible Solution

• It should use a pre-cached version of OptionManager when I use babelrc: false
• It should maybe cache OptionManager instances on a per-directory basis
• It should use the ignore regexps earlier to avoid creating the OptionManager instances

[babel-bot]

Hey @Swatinem! We really appreciate you taking the time to report an issue. The collaborators
on this project attempt to help as many people as possible, but we're a limited number of volunteers,
so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack
community that typically always has someone willing to help. You can sign-up here
for an invite.

[grantlouisherman]

hey @nicolo-ribaudo is it possible for me to take a look?

[nicolo-ribaudo]

Sure!

[grantlouisherman]

Hey @nicolo-ribaudo I wanted to run my approach by you. Is it better to send it to you via this ticket or just open a PR to get your eyes on it?

[JLHwung]

@grantlouisherman You can open a draft PR so people can give early feedback.