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preset-env: warning about useBuiltIns should go into stderr #9977

andreineculau opened this issue May 14, 2019 · 2 comments


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commented May 14, 2019

Bug Report

Current Behavior
Using the useBuiltIns options without declaring a core-js version produces a warning that is flushed to stdout.

Input Code

"\nWARNING: We noticed you're using the `useBuiltIns` option without declaring a " +
"core-js version. Currently, we assume version 2.x when no version " +
"is passed. Since this default version will likely change in future " +
"versions of Babel, we recommend explicitly setting the core-js version " +
"you are using via the `corejs` option.\n" +
"\nYou should also be sure that the version you pass to the `corejs` " +
"option matches the version specified in your `package.json`'s " +
"`dependencies` section. If it doesn't, you need to run one of the " +
"following commands:\n\n" +
" npm install --save core-js@2 npm install --save core-js@3\n" +
" yarn add core-js@2 yarn add core-js@3\n",

Expected behavior/code
Anything not intended for success output should go into stderr. Examples: debug/warnings/errors/progress reports, etc. This has been mentioned before targeting another part of the source code

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



  • Babel version(s): 7.4.4
  • Node/npm version: Node/12, npm/6 (targeting Node 8)
  • OS: OSX
  • Monorepo: no
  • How you are using Babel: cli

Possible Solution

console.log -> console.warn/console.error


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commented May 14, 2019

Hey @andreineculau! 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
that typically always has someone willing to help. You can sign-up here
for an invite.


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commented May 14, 2019

Yeah, It should be console.warn. Do you want to open a PR?

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