WIP: proposal for running micro-tasks in angular scope

Author: mhevery

lib/core/scope.dart

@@ -539,6 +539,7 @@ class RootScope extends Scope {
             _scopeStats)
   {
     _zone.onTurnDone = apply;
+    _zone._onScheduleMicrotask = runAsync;
     _zone.onError = (e, s, ls) => _exceptionHandler(e, s);
   }
 
@@ -666,11 +667,15 @@ class RootScope extends Scope {
 
   // QUEUES
   void runAsync(fn()) {
-    var chain = new _FunctionChain(fn);
-    if (_runAsyncHead == null) {
-      _runAsyncHead = _runAsyncTail = chain;
+    if (_state == null || _state == RootScope.STATE_APPLY || _state == RootScope.STATE_DIGEST) {
+      var chain = new _FunctionChain(fn);
+      if (_runAsyncHead == null) {
+        _runAsyncHead = _runAsyncTail = chain;
+      } else {
+        _runAsyncTail = _runAsyncTail._next = chain;
+      }
     } else {
-      _runAsyncTail = _runAsyncTail._next = chain;
+      throw "Flush phase can not schedule microtasks.";
     }
   }
 

test/core/zone_spec.dart

@@ -154,17 +154,23 @@ void main() {
     it('should call onTurnDone for a scheduleMicrotask in onTurnDone', async((Logger log) {
       var ran = false;
       zone.onTurnDone = () {
+        log('onTurnDone(begin)');
         if (!ran) {
           scheduleMicrotask(() { ran = true; log('onTurnAsync'); });
         }
-        log('onTurnDone');
+        log('onTurnDone(end)');
+      };
+      zon.onSchedulMicrotask = (microTaskFn) {
+        log('onScheduleMicrotask(begin)');
+        microTaskFn();
+        log('onScheduleMicrotask(end)');
       };
       zone.run(() {
         log('run');
       });
       microLeap();
 
-      expect(log.result()).toEqual('onTurnStart; run; onTurnDone; onTurnStart; onTurnAsync; onTurnDone');
+      expect(log.result()).toEqual('onTurnStart; run; onTurnDone(begin); onScheduleMicrotask(begin); onTurnAsync; onScheduleMicrotask(begin); onTurnDone(end)');
     }));