WIP: Add antiResolve

[erights]

WIP Adds a Promise.antiResolve(promise) -> presence static method to Promise, to provide synchronous access from a fulfilled handled promise to its fulfillment. This would enable, for example, Purse.depositAll(paymentP) to avoid an extra turn by insisting that Promise.antiResolve(paymentP) not be undefined. In that case, it should be the payment itself, which can then be handled synchronously.

Avoiding the extra turn in that case makes it possible for the purse to process such messages in the order then come in, and makes it possible for the client, in the common case, to avoid forcing a round trip which would lose the benefits of promise pipelining.

WIP because of missing tests, need to bikeshed name and where to put it, and explaining better what this is and why it is needed. Not a candidate for merging until then, but making available as a pull request now to gather feedback.

[michaelfig]

Bikeshedding a name: How about Promise.getPresence(myP)?

Having looked at your ERTP patch, this makes sense to me as an API. I think it really should live on the Promise global, as it is part of the support that should be available for standard handled promises.

[warner]

note: this PR needs to be migrated to the new monorepo in agoric-sdk

[michaelfig]

Maybe: HandledPromise.unwrap(p) which throws if p is not a resolved handled promise, otherwise return the presence/fulfilled value.

Holidays are here, so I'd like to unwrap my presence.

[erights]

I like unwrap

[erights]

The point of this change, adding HandledPromise.unwrap, was already merged by another PR by @michaelfig , so closing this one.

Noting that we're likely to remove HandledPromise.unwrap anyway, as it is too hard to use correctly.