[PEAK] Re: trellis.Set.discard

[Sergey Schetinin]

After a lot of experimenting, this code seems to provide something useful info:


from pprint import pprint as pp


class CV(Component):
    v = attr(False)
    s = make(Set)

    @maintain
    def maintain(self):
        #print 'in maintain'
        if self.v:
            act = 'add'
            self.s.add(1)
        else:
            act = 'discard'
            self.s.discard(1)
            #task.s.remove(1)
        @on_undo
        def undo(): print "UNDO", act

    @perform
    def perform(self):
        print '-'*20, self.v, self.s



def doit():
    cv = CV()
    print 'undo history:'
    pp(ctrl.undo)
    cv.v = True

print 'TASK'
@atomically
def naked():
    #cell = trellis.Value()
    cell = trellis.Cell(lambda: None)
    ctrl.current_listener = cell
    doit()
    #pp(ctrl.writes)
    ctrl._process_writes(cell)
    ctrl.current_listener = None

print
print 'ATOMICALLY'
atomically(doit)



It shows two differences, first is that maintain rule is not rolled
back at all for @atomically, maintain just runs twice, which is
strange.
Second is that inside doit() the undo histrory for @atomically has two
more items, but this doesn't matter, because they never run.

So the question is why undo isn't triggered for normal atomic call,
but it is for task-style invoke?