support subpath pattern exports

[turadg]

What is the Problem Being Solved?

Endo's bundler doesn't yet support subpath patterns in the package exports property.

This breaks imports from packages that use it. E.g. in this build

Description of the Design

Support it. :)

Security Considerations

Scaling Considerations

Test Plan

Compatibility Considerations

Upgrade Considerations

[kriskowal]

I took a moment to look into this, to gauge how much of a lift it really would be.

A closer read of the docs tells me that the DSL for subpath patterns seems to merely be strings split on '*', with no affordance for escaping asterisks and not the much more sophisticated glob DSL. So, the problem reduces to RegExp.escape. We don’t have RegExp.escape yet and the shim is a little overwrought for our needs. So I grabbed a copy and whittled it down to the essential core and got it to pass all the same tests.

https://gist.github.com/kriskowal/35c435f2d99b57a3f1cd00e2b4c407aa

This largely reduces because we’re able to rely on code point iteration and can safely dispatch methods of intrinsics under Hardened JavaScript.

I think it’d be reasonable to @endo/regexp-escape a ponyfill and just inline the subpath matching in @endo/compartment-mapper.