import.meta.resolve implementation

[guybedford]

This implements an import.meta.resolve function on the SystemJS context in core allowing contextual resolution for native ES modules converted into the SystemJS format.

This is as landed in ES Module Shims here - guybedford/es-module-shims#89.

By default the implementation is async to support an async resolver function. In future if this is ever made sync that will be an easier hence starting with an async hook makes the most sense. This also matches the implementation under --experimental-import-meta-resolve in Node.js.

[github-actions]

core

File by file impact

File	Transform	Diff	master	import-meta-resolve	Event
dist/s.js	none	+149	21,553	21,702	changed
	gzip	+16	6,117	6,133
	brotli	+9	5,278	5,287
dist/s.min.js	none	+76	6,559	6,635	changed
	gzip	+14	2,638	2,652
	brotli	+19	2,359	2,378
dist/system-node.cjs	none	+141	200,985	201,126	changed
	gzip	+16	51,345	51,361
	brotli	+32	43,451	43,483
dist/system.js	none	+149	31,999	32,148	changed
	gzip	+18	8,631	8,649
	brotli	+8	7,479	7,487
dist/system.min.js	none	+76	10,584	10,660	changed
	gzip	+13	4,084	4,097
	brotli	+15	3,651	3,666

extras

File by file impact

Pull request have no impact on extras files.

_{Generated by github pull request filesize impact}

[joeldenning]

Looks good! Perhaps we should update the docs for this, too, to mention that it's available?

https://github.com/systemjs/systemjs/blob/master/docs/system-register.md#format-definition

[guybedford]

Released in 6.5.0.