Change useBuiltIns to usage

[timkelty]

Resolves #1470

[edmorley]

Thank you for the PR :-)

[timkelty]

@edmorley do you think each preset should have a "If you need polyfills in your code…" callout?

Not sure why currently only Library and React have them currently…

[edmorley]

Yeah think adding to all of them makes sense (or at least all of the web related ones; less sure about Node)

[timkelty]

Yeah think adding to all of them makes sense (or at least all of the web related ones; less sure about Node)

I added the note to everything that used useBuiltIns: usage, which included Node.

[edmorley]

Remove note from react

I think we should still include the note for the React preset. I think maybe you saw the useBuiltIns: true mention in React and so why the docs entry was removed for that? If so, the useBuiltIns: true is actually a different setting with the same name - it's passed to the React babel preset (see docs here) rather than preset-env.

Perhaps a comment next to it emphasising it's different would be useful, since it confused me yesterday too when reviewing the PR?

[timkelty]

@edmorley with the eagle eye! Good catch. 🦅 👁

[edmorley]

Perhaps a comment next to it emphasising it's different would be useful, since it confused me yesterday too when reviewing the PR?

I'm really sorry I meant as a code comment in packages/react/index.js rather than in the README. Though happy to go with whatever you think is best :-)

[timkelty]

@edmorley yeah I thought about that after I pushed…one sec. Think I should keep both?

[edmorley]

@timkelty Babel 7.7.0 (released in last day or so) added a new useSpread option to the React preset (only) that supersedes the useBuiltins React option, so I'll likely be replacing the option once I've read up more.

Also even if we don't switch to useSpread, users will rarely need to change the React preset option, since whatever the React plugins output gets transpiled after - ie: using built-ins for the React output is desirable either way, so something we perhaps don't need to worry users about.

[edmorley]

Thank you :-)