The `add-endpoint!` call is changed in two ways:
- the old `assertion-fn` has become `update-fn`, yielding both
an assertion *and* an optional handler, because if the handler
depends on a field which changes, previously the handler wasn't
being updated
- a new parameter, `dynamic?`, can be set to #f (it's usually #t)
to ensure that the assertion and skeleton-interest are calculated
only once ever, and are not connected to the dataflow machinery.
The first change makes it possible for the `(later-than (deadline))`
pattern, where `deadline` is a field, to work; the second change makes
`during` and `during/spawn` work correctly in the face of field
updates.
This repairs a bug regarding crashes in a new actor's boot-proc.
Previously, if boot-proc raised an exception, the initial assertions
would stick around forever. By changing adhoc-assertions to a bag
rather than a set, and putting the initial assertions in the bag, we
put them somewhere they are guaranteed to be processed during actor
termination, even when an exception is signalled during boot.
This is an API change wrt the previous Syndicate implementation:
assert!/retract! now have bag semantics, not set semantics. We can add
set-semantics APIs if we end up needing them, of course, layered on
top of the bag implementation.
Tony Garnock-Jones