Protocol parsing in URL resolution

[guybedford]

Currently we determine an absolute URL form based on the existence of :, but there are valid use cases for having : in a relative URL.

We should update the code at https://github.com/ModuleLoader/es-module-loader/blob/master/core/resolve.js#L12 to provide proper protocol parsing, following some subset of the rules at https://url.spec.whatwg.org/#host-parsing.

The important thing is that this code is on the performance shortpath so it's nice to do as little work as possible.

The regex /^[^:/?#]+:/ may well be enough to rule out the common cases.

[guybedford]

/[^/]+:/ may be all that is necessary here since the rules of URLs restrict bare names to those without : in the first part, which is what we're really trying to detect here.

[guybedford]

Released in 2.2.0.