Clear up presences vs. remotables

[michaelfig]

This implements the first part of the #804 plan for explicitly creating remotables via the @agoric/marshal Remotable() function.

Remotable and getInterfaceOf should be shared across marshal systems within the vat that imports them. I explicitly provide them to the liveSlots caller in order to expose to the vat code that uses it, rather than bundling a new copy of @agoric/marshal and getting a different instance of the WeakMap that keeps the interface information.

This is the smallest step forward that properly solves #792 without needing more far-reaching changes.

Here is some annotated REPL output:

// Show how presences print
command[0] home
history[0] {"chainTimerService":[Presence o-50]{},"sharingService":[Presence o-51]{},"contractHost":[Presence o-52]{},"registrar":[Presence o-53]{},"zoe":[Presence o-54]{},"localTimerService":[Presence o-55]{},"uploads":[Presence o-56]{},"spawner":[Presence o-57]{},"wallet":[Presence o-58]{},"http":[Presence o-59]{}}
// Try making a remotable from an array
command[2] a = []
history[2] []
command[3] Remotable('Foo', {abc: 1}, a)
history[3] exception: Error: Arrays cannot be pass-by-presence
// Note that there is no mutation.
command[4] a
history[4] []
// Try adding a property to an empty remotable.
command[5] Remotable('Foo', {abc: 1})
history[5] exception: Error: cannot serialize objects with non-methods like the .abc in [Foo]
// Add a method to an empty remotable.
command[6] Remotable('Foo', {abc() { return 'def' }})
history[6] [Foo]{"abc":[Function abc]}
// Call the method.
command[7] history[6].abc()
history[7] "def"
// Use tildot.
command[8] history[6]~.abc()
history[8] "def"
// Try making a function into a remotable.
command[9] Remotable('Foo', {abc() { return 'def' }}, a => a + 1)
history[9] exception: Error: cannot serialize non-objects like a => a + 1
// Demonstrate that getInterfaceOf shows the iface we attached.
command[11] getInterfaceOf(history[6])
history[11] "Foo"

[erights]

Just a start on review.

[michaelfig]

Please, all, take a look at tc39/proposal-eventual-send#11

[erights]

@michaelfig please let me know when this has been updated to the latest eventual send API and terminology.

[michaelfig]

@michaelfig please let me know when this has been updated to the latest eventual send API and terminology.

@erights I moved to the Presence vs Remotable distinction we now make. However, I will change to Promise.delegate in a PR after this one. I really want to land this one first, and get it in!

So, this is ready for review.

[erights]

Excited to see this, thanks!

[erights]

LGTM once the copying of errors are fixed.