Deal with realms?

[domenic]

@bzbarsky had some good feedback on specifying the realms in which various operations run:

One issue I just realized, as I was considering how to implement some of this stuff in automated ways. All the terms in the "Creating Promises"
are implicitly assuming operation in a particular realm. Same for the ones in "Aggregating Promises" and the definition of "Transforming p with onFulfilled and onRejected". Same thing for the "Promise Arguments Should Be Cast" guidance.

They need to either explicitly specify which realm is used somehow or all consumers (that is, specs using this terminology) need to do it.

This is particularly relevant when functions from one realm are invoked on a this object or arguments from another realm (and possible from multiple other realms); the algorithm defining the behavior of the function may need to think carefully about what realms are used for which operations in that situation...

As per the follow-ups in the thread, this might not be promise-specific, but it's possibly something this guide could handle in its shorthand definitions.

[domenic]

This is out of scope. domenic/promises-unwrapping#108 is starting to make progress on these issues, but it is a normative specification-level thing between the ES and HTML specs, and not something for the guide.

[bzbarsky]

Actually, the issues in domenic/promises-unwrapping#108 are a bit separate. Those are about incumbent and entry globals, but this issue is about object creation and realms, which is unrelated to incumbent/entry globals.

[domenic]

Ah, you're totally right; I should have re-read my own post. Reopening.

[annevk]

https://www.w3.org/Bugs/Public/show_bug.cgi?id=24652

[domenic]

@bzbarsky, review https://github.com/w3ctag/promises-guide#a-note-on-realms ?

[bzbarsky]

@domenic That looks good, thanks!