A one-method object is added to the redemption object when exit is onDemand

[DavidBruant]

agoric-sdk/packages/zoe/src/zoe.js

Lines 444 to 448 in 7ceebe5

	} else if (exitKind === 'onDemand') {
	redemptionResult.cancelObj = {
	cancel: () =>
	completeOffers(instanceHandle, harden([offerHandle])),
	};

I feel this could be simplified into:

redemptionResult.cancel = () => completeOffers(instanceHandle, harden([offerHandle])),

.cancelObj.cancel() feels a bit awkward

[katelynsills]

Yeah, agreed that redemptionResult.cancel() would be the best way to design this. However, our infrastructure below Zoe (@agoric/marshal) doesn't allow for this option. In marshal:

// objects can only be passed in one of two/three forms:
// 1: pass-by-presence: all properties (own and inherited) are methods,
// the object itself is of type object, not function
// 2: pass-by-copy: all string-named own properties are data, not methods
// the object must inherit from Object.prototype or null
// 3: the empty object is pass-by-presence, for identity comparison

Because the redemption result is a record already with seat and payout, we can't have a method as well.

[katelynsills]

I'm going to close this, but we should probably document this design decision someplace so it doesn't always look so dumb :)

[erights]

we should probably document this design decision someplace so it doesn't always look so dumb

#804 (comment) refers to the new grand plan @michaelfig and I settled today, that would fix this. It introduces a better way to express presences, that solve a large number of problems. Eventually (not soon) we can make function presences that can be remotely invoked with tildot. If we were first designing Zoe after this transition, cancel may very well have been such a function presence.

History dependent design is always painful, but is an inevitable price of success.

[DavidBruant]

However, our infrastructure below Zoe (@agoric/marshal) doesn't allow for this option.

Yeah, now i remember, we've already had this discussion and i had forgotten
Sorry about that
and thanks for the details