HTML Integration with ESM Source Phase

[guybedford]

What is the issue with the HTML Standard?

With the WebAssembly ESM integration now merged in #10380 using the source phase imports proposal, there is a follow-on proposal for JavaScript implementing the source phase object to reflect uninstantiated JS modules in the "ESM Phase Imports" proposal - https://github.com/tc39/proposal-esm-phase-imports.

This proposal provides a new primitive representing an arbitrary JS source that should enable better JS virtualization as well as integration with JS module expressions and JS module declarations.

The primitive has limited use on its own, but we've been able to identify worker instantiation and worker JS source transfer as possible interesting applications here, which are being used to motivate the proposal's progression.

The proposal spec text for the ESM phase imports proposal is largely complete at this point in https://tc39.es/proposal-esm-phase-imports/, therefore the remaining important integration to consider the integration of these worker use cases into HTML.

Opening this as an issue to track this integration, and to get further feedback on the HTML side. @annevk previously suggested it might also be worth adding this to the WHATNOT agenda as well for further discussion, which I would be glad to join as well whenever there is space on the agenda.

[annevk]

When @guybedford can make it, it would be good to briefly go over this in WHATNOT I think. Probably after TPAC.

[guybedford]

That would be great - I'll tentatively add this to my calendar for 3 October. That timing would also work well to bring any feedback to TC39 the next week.