add externals config for prop-types?

[jochenberger]

I think that you shouldn't package prop-types in the UMD modules.

[timdorr]

This is technically proper, but I'm wondering how many people are just importing React/ReactDOM and will have a big breakage when this kind of thing lands.

[jochenberger]

I wonder if we could provide a migration path.

[timdorr]

It's all or nothing, unfortunately. The only other way around it is to hand-build the UMD version and hack in some sort of externals check to do a deprecation warning if it's not defined externally. But that seems really risky and brittle.

A minor release with this change shouldn't be a problem. Most UMD consumers should be able to manage their deps in some way, so they should see the requirement for prop-types and add that in.

[mjackson]

I think we'll continue to leave prop-types in our build for now. Thanks for the suggestion though, @jochenberger :)