macros: add onStart and onStop

The onStart and onStop macros will be called as actors start and
stop. This can be used to call `quit`, since the async dispatcher
will run empty and raise an error otherwise.

src/syndicate.nim

@@ -11,6 +11,8 @@ export dataspaces.Facet
 export dataspaces.FieldId
 export dataspaces.Fields
 export dataspaces.addEndpoint
+export dataspaces.addStartScript
+export dataspaces.addStopScript
 export dataspaces.defineObservableProperty
 export dataspaces.generateId
 export dataspaces.hash
@@ -178,4 +180,4 @@ template syndicate*(name: string; dataspaceBody: untyped): untyped =
   proc bootProc(rootFacet: Facet) =
     proc getCurrentFacet(): Facet {.inject, used.} = rootFacet
     dataspaceBody
-  waitFor bootModule(name, bootProc)
+  asyncCheck bootModule(name, bootProc)

src/syndicate/dataspaces.nim

@@ -253,6 +253,8 @@ proc abort(facet; emitPatches: bool) =
   for child in facet.children.values:
     child.abort(emitPatches)
   facet.retractAssertionsAndSubscriptions(emitPatches)
+  for s in facet.stopScripts: s(facet)
+    # call stopScripts immediately
 
 proc enqueueScriptAction(actor; action: Action) =
   actor.pendingActions.add(action)
@@ -342,10 +344,13 @@ proc scheduleScript*(facet; prio: Priority; script: Script[void]) =
 proc scheduleScript*(facet; script: Script[void]) =
   facet.actor.scheduleTask(pNormal, facet.wrap(script))
 
-proc addStartScript(facet; s: Script[void]) =
+proc addStartScript*(facet; s: Script[void]) =
   facet.ensureFacetSetup("onStart")
   facet.scheduleScript(pNormal, s)
 
+proc addStopScript*(facet; s: Script[void]) =
+  facet.stopScripts.add(s)
+
 proc addFacet(actor; parentFacet: Option[Facet]; bootScript: Script[void]; checkInScript = false) =
   if checkInScript and parentFacet.isSome:
     assert parentFacet.get.inScript
@@ -530,6 +535,8 @@ proc step(g: Ground) =
   if g.dataspace.runTasks():
     asyncdispatch.callSoon: step(g)
   else:
+    for actor in g.dataspace.actors.values:
+      terminate(actor, false)
     for sh in g.stopHandlers:
       sh(g.dataspace)
     reset g.stopHandlers

tests/test_dsl.nim

@@ -7,15 +7,17 @@ import syndicate
 const
   BoxState = RecordClass(label: symbol"box-state", arity: 1)
   SetBox = RecordClass(label: symbol"set-box", arity: 1)
+    # TODO: hide RecordClass behind Assertion and Message types
 
 syndicate "test_dsl":
 
   spawn "box":
     field(currentValue, int, 0)
-    assert(BoxState, currentValue)
+    assert(BoxState, currentValue.get)
     stopIf currentValue.get == 10:
       echo "box: terminating"
     onMessage(SetBox) do (newValue: int):
+      # The SetBox message is unpacked to `newValue: int`
       echo "box: taking on new value ", newValue
       currentValue.set(newValue)
 
@@ -27,3 +29,9 @@ syndicate "test_dsl":
       send(SetBox, v+1)
     onRetracted(BoxState) do (_):
       echo "client: box state disappeared"
+    onStop:
+      quit(0) # Quit explicitly rather than let the dispatcher run empty.
+
+runForever()
+  # The dataspace is driven by the async dispatcher.
+  # Without `runForever` this module would exit immediately.