V8 Microtask Queue & API

This patch generalizes Object.observe callbacks and promise resolution into a FIFO queue called a "microtask queue".

It also exposes new V8 API which exposes the microtask queue to the embedder. In particular, it allows the embedder to

-schedule a microtask (EnqueueExternalMicrotask)
-run the microtask queue (RunMicrotasks)
-control whether the microtask queue is run automatically within V8 when the last script exits (SetAutorunMicrotasks).

R=dcarney@chromium.org, rossberg@chromium.org, dcarney, rossberg, svenpanne
BUG=

Review URL: https://codereview.chromium.org/154283002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19344 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

include/v8.h

@@ -4578,6 +4578,22 @@ class V8_EXPORT V8 {
    */
   static void RemoveCallCompletedCallback(CallCompletedCallback callback);
 
+  /**
+   * Experimental: Runs the Microtask Work Queue until empty
+   */
+  static void RunMicrotasks(Isolate* isolate);
+
+  /**
+   * Experimental: Enqueues the callback to the Microtask Work Queue
+   */
+  static void EnqueueMicrotask(Isolate* isolate, Handle<Function> microtask);
+
+   /**
+   * Experimental: Controls whether the Microtask Work Queue is automatically
+   * run when the script call depth decrements to zero.
+   */
+  static void SetAutorunMicrotasks(Isolate *source, bool autorun);
+
   /**
    * Initializes from snapshot if possible. Otherwise, attempts to
    * initialize from scratch.  This function is called implicitly if
@@ -5398,7 +5414,7 @@ class Internals {
   static const int kNullValueRootIndex = 7;
   static const int kTrueValueRootIndex = 8;
   static const int kFalseValueRootIndex = 9;
-  static const int kEmptyStringRootIndex = 147;
+  static const int kEmptyStringRootIndex = 148;
 
   static const int kNodeClassIdOffset = 1 * kApiPointerSize;
   static const int kNodeFlagsOffset = 1 * kApiPointerSize + 3;

src/api.cc

@@ -6293,6 +6293,25 @@ void V8::AddCallCompletedCallback(CallCompletedCallback callback) {
 }
 
 
+void V8::RunMicrotasks(Isolate* isolate) {
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  i::HandleScope scope(i_isolate);
+  i::V8::RunMicrotasks(i_isolate);
+}
+
+
+void V8::EnqueueMicrotask(Isolate* isolate, Handle<Function> microtask) {
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  ENTER_V8(i_isolate);
+  i::Execution::EnqueueMicrotask(i_isolate, Utils::OpenHandle(*microtask));
+}
+
+
+void V8::SetAutorunMicrotasks(Isolate* isolate, bool autorun) {
+  reinterpret_cast<i::Isolate*>(isolate)->set_autorun_microtasks(autorun);
+}
+
+
 void V8::RemoveCallCompletedCallback(CallCompletedCallback callback) {
   i::V8::RemoveCallCompletedCallback(callback);
 }

src/bootstrapper.cc

@@ -1582,6 +1582,9 @@ void Genesis::InstallNativeFunctions() {
 
 void Genesis::InstallExperimentalNativeFunctions() {
   INSTALL_NATIVE(JSFunction, "RunMicrotasks", run_microtasks);
+  INSTALL_NATIVE(JSFunction, "EnqueueExternalMicrotask",
+                 enqueue_external_microtask);
+
   if (FLAG_harmony_proxies) {
     INSTALL_NATIVE(JSFunction, "DerivedHasTrap", derived_has_trap);
     INSTALL_NATIVE(JSFunction, "DerivedGetTrap", derived_get_trap);

src/contexts.h

@@ -167,6 +167,7 @@ enum BindingFlags {
   V(ERROR_MESSAGE_FOR_CODE_GEN_FROM_STRINGS_INDEX, Object, \
     error_message_for_code_gen_from_strings) \
   V(RUN_MICROTASKS_INDEX, JSFunction, run_microtasks) \
+  V(ENQUEUE_EXTERNAL_MICROTASK_INDEX, JSFunction, enqueue_external_microtask) \
   V(TO_COMPLETE_PROPERTY_DESCRIPTOR_INDEX, JSFunction, \
     to_complete_property_descriptor) \
   V(DERIVED_HAS_TRAP_INDEX, JSFunction, derived_has_trap) \
@@ -318,6 +319,7 @@ class Context: public FixedArray {
     ALLOW_CODE_GEN_FROM_STRINGS_INDEX,
     ERROR_MESSAGE_FOR_CODE_GEN_FROM_STRINGS_INDEX,
     RUN_MICROTASKS_INDEX,
+    ENQUEUE_EXTERNAL_MICROTASK_INDEX,
     TO_COMPLETE_PROPERTY_DESCRIPTOR_INDEX,
     DERIVED_HAS_TRAP_INDEX,
     DERIVED_GET_TRAP_INDEX,

src/execution.cc

@@ -368,6 +368,20 @@ void Execution::RunMicrotasks(Isolate* isolate) {
 }
 
 
+void Execution::EnqueueMicrotask(Isolate* isolate, Handle<Object> microtask) {
+  bool threw = false;
+  Handle<Object> args[] = { microtask };
+  Execution::Call(
+      isolate,
+      isolate->enqueue_external_microtask(),
+      isolate->factory()->undefined_value(),
+      1,
+      args,
+      &threw);
+  ASSERT(!threw);
+}
+
+
 bool StackGuard::IsStackOverflow() {
   ExecutionAccess access(isolate_);
   return (thread_local_.jslimit_ != kInterruptLimit &&

src/execution.h

@@ -175,6 +175,7 @@ class Execution : public AllStatic {
                                                   bool* has_pending_exception);
 
   static void RunMicrotasks(Isolate* isolate);
+  static void EnqueueMicrotask(Isolate* isolate, Handle<Object> microtask);
 };
 
 

src/heap.cc

@@ -3274,6 +3274,15 @@ bool Heap::CreateInitialObjects() {
   }
   set_observation_state(JSObject::cast(obj));
 
+  // Allocate object to hold object microtask state.
+  { MaybeObject* maybe_obj = AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
+    if (!maybe_obj->ToObject(&obj)) return false;
+  }
+  { MaybeObject* maybe_obj = AllocateJSObjectFromMap(Map::cast(obj));
+    if (!maybe_obj->ToObject(&obj)) return false;
+  }
+  set_microtask_state(JSObject::cast(obj));
+
   { MaybeObject* maybe_obj = AllocateSymbol();
     if (!maybe_obj->ToObject(&obj)) return false;
   }

src/heap.h

@@ -203,7 +203,8 @@ namespace internal {
       EmptySlowElementDictionary)                                              \
   V(Symbol, observed_symbol, ObservedSymbol)                                   \
   V(FixedArray, materialized_objects, MaterializedObjects)                     \
-  V(FixedArray, allocation_sites_scratchpad, AllocationSitesScratchpad)
+  V(FixedArray, allocation_sites_scratchpad, AllocationSitesScratchpad)        \
+  V(JSObject, microtask_state, MicrotaskState)
 
 #define ROOT_LIST(V)                                  \
   STRONG_ROOT_LIST(V)                                 \

src/isolate.h

@@ -359,7 +359,8 @@ typedef List<HeapObject*> DebugObjectCache;
   /* AstNode state. */                                                         \
   V(int, ast_node_id, 0)                                                       \
   V(unsigned, ast_node_count, 0)                                               \
-  V(bool, microtask_pending, false)                                           \
+  V(bool, microtask_pending, false)                                            \
+  V(bool, autorun_microtasks, true)                                            \
   V(HStatistics*, hstatistics, NULL)                                           \
   V(HTracer*, htracer, NULL)                                                   \
   V(CodeTracer*, code_tracer, NULL)                                            \

src/object-observe.js

@@ -390,11 +390,13 @@ function ObserverEnqueueIfActive(observer, objectInfo, changeRecord,
   }
 
   var callbackInfo = CallbackInfoNormalize(callback);
-  if (!observationState.pendingObservers)
+  if (IS_NULL(observationState.pendingObservers)) {
     observationState.pendingObservers = nullProtoObject();
+    GetMicrotaskQueue().push(ObserveMicrotaskRunner);
+    %SetMicrotaskPending(true);
+  }
   observationState.pendingObservers[callbackInfo.priority] = callback;
   callbackInfo.push(changeRecord);
-  %SetMicrotaskPending(true);
 }
 
 function ObjectInfoEnqueueExternalChangeRecord(objectInfo, changeRecord, type) {
@@ -583,7 +585,6 @@ function ObserveMicrotaskRunner() {
     }
   }
 }
-RunMicrotasks.runners.push(ObserveMicrotaskRunner);
 
 function SetupObjectObserve() {
   %CheckIsBootstrapping();

src/promise.js

@@ -173,37 +173,29 @@ function PromiseCatch(onReject) {
 }
 
 function PromiseEnqueue(value, tasks) {
-  promiseEvents.push(value, tasks);
+  GetMicrotaskQueue().push(function() {
+    for (var i = 0; i < tasks.length; i += 2) {
+      PromiseHandle(value, tasks[i], tasks[i + 1])
+    }
+  });
+
   %SetMicrotaskPending(true);
 }
 
-function PromiseMicrotaskRunner() {
-  var events = promiseEvents;
-  if (events.length > 0) {
-    promiseEvents = new InternalArray;
-    for (var i = 0; i < events.length; i += 2) {
-      var value = events[i];
-      var tasks = events[i + 1];
-      for (var j = 0; j < tasks.length; j += 2) {
-        var handler = tasks[j];
-        var deferred = tasks[j + 1];
-        try {
-          var result = handler(value);
-          if (result === deferred.promise)
-            throw MakeTypeError('promise_cyclic', [result]);
-          else if (IsPromise(result))
-            result.chain(deferred.resolve, deferred.reject);
-          else
-            deferred.resolve(result);
-        } catch(e) {
-          // TODO(rossberg): perhaps log uncaught exceptions below.
-          try { deferred.reject(e) } catch(e) {}
-        }
-      }
-    }
+function PromiseHandle(value, handler, deferred) {
+  try {
+    var result = handler(value);
+    if (result === deferred.promise)
+      throw MakeTypeError('promise_cyclic', [result]);
+    else if (IsPromise(result))
+      result.chain(deferred.resolve, deferred.reject);
+    else
+      deferred.resolve(result);
+  } catch(e) {
+    // TODO(rossberg): perhaps log uncaught exceptions below.
+    try { deferred.reject(e) } catch(e) {}
   }
 }
-RunMicrotasks.runners.push(PromiseMicrotaskRunner);
 
 
 // Multi-unwrapped chaining with thenable coercion.

src/runtime.cc

@@ -14596,6 +14596,21 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_SetMicrotaskPending) {
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_RunMicrotasks) {
+  HandleScope scope(isolate);
+  ASSERT(args.length() == 0);
+  Execution::RunMicrotasks(isolate);
+  return isolate->heap()->undefined_value();
+}
+
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_GetMicrotaskState) {
+  SealHandleScope shs(isolate);
+  ASSERT(args.length() == 0);
+  return isolate->heap()->microtask_state();
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_GetObservationState) {
   SealHandleScope shs(isolate);
   ASSERT(args.length() == 0);

src/runtime.h

@@ -308,6 +308,9 @@ namespace internal {
   /* ES5 */ \
   F(ObjectFreeze, 1, 1) \
   \
+  /* Harmony Microtasks */ \
+  F(GetMicrotaskState, 0, 1) \
+  \
   /* Harmony modules */ \
   F(IsJSModule, 1, 1) \
   \
@@ -351,6 +354,7 @@ namespace internal {
   \
   /* Harmony events */ \
   F(SetMicrotaskPending, 1, 1) \
+  F(RunMicrotasks, 0, 1) \
   \
   /* Harmony observe */ \
   F(IsObserved, 1, 1) \

src/v8.cc

@@ -148,15 +148,16 @@ void V8::RemoveCallCompletedCallback(CallCompletedCallback callback) {
 
 void V8::FireCallCompletedCallback(Isolate* isolate) {
   bool has_call_completed_callbacks = call_completed_callbacks_ != NULL;
-  bool microtask_pending = isolate->microtask_pending();
-  if (!has_call_completed_callbacks && !microtask_pending) return;
+  bool run_microtasks = isolate->autorun_microtasks() &&
+                        isolate->microtask_pending();
+  if (!has_call_completed_callbacks && !run_microtasks) return;
 
   HandleScopeImplementer* handle_scope_implementer =
       isolate->handle_scope_implementer();
   if (!handle_scope_implementer->CallDepthIsZero()) return;
   // Fire callbacks.  Increase call depth to prevent recursive callbacks.
   handle_scope_implementer->IncrementCallDepth();
-  if (microtask_pending) Execution::RunMicrotasks(isolate);
+  if (run_microtasks) Execution::RunMicrotasks(isolate);
   if (has_call_completed_callbacks) {
     for (int i = 0; i < call_completed_callbacks_->length(); i++) {
       call_completed_callbacks_->at(i)();
@@ -166,6 +167,21 @@ void V8::FireCallCompletedCallback(Isolate* isolate) {
 }
 
 
+void V8::RunMicrotasks(Isolate* isolate) {
+  if (!isolate->microtask_pending())
+    return;
+
+  HandleScopeImplementer* handle_scope_implementer =
+      isolate->handle_scope_implementer();
+  ASSERT(handle_scope_implementer->CallDepthIsZero());
+
+  // Increase call depth to prevent recursive callbacks.
+  handle_scope_implementer->IncrementCallDepth();
+  Execution::RunMicrotasks(isolate);
+  handle_scope_implementer->DecrementCallDepth();
+}
+
+
 void V8::InitializeOncePerProcessImpl() {
   FlagList::EnforceFlagImplications();
 

src/v8.h

@@ -101,6 +101,8 @@ class V8 : public AllStatic {
   static void RemoveCallCompletedCallback(CallCompletedCallback callback);
   static void FireCallCompletedCallback(Isolate* isolate);
 
+  static void RunMicrotasks(Isolate* isolate);
+
   static v8::ArrayBuffer::Allocator* ArrayBufferAllocator() {
     return array_buffer_allocator_;
   }

src/v8natives.js

@@ -1889,10 +1889,30 @@ SetUpFunction();
 // Eventually, we should move to a real event queue that allows to maintain
 // relative ordering of different kinds of tasks.
 
-RunMicrotasks.runners = new InternalArray;
+function GetMicrotaskQueue() {
+  var microtaskState = %GetMicrotaskState();
+  if (IS_UNDEFINED(microtaskState.queue)) {
+    microtaskState.queue = new InternalArray;
+  }
+  return microtaskState.queue;
+}
 
 function RunMicrotasks() {
   while (%SetMicrotaskPending(false)) {
-    for (var i in RunMicrotasks.runners) RunMicrotasks.runners[i]();
+    var microtaskState = %GetMicrotaskState();
+    if (IS_UNDEFINED(microtaskState.queue))
+      return;
+
+    var microtasks = microtaskState.queue;
+    microtaskState.queue = new InternalArray;
+
+    for (var i = 0; i < microtasks.length; i++) {
+      microtasks[i]();
+    }
   }
 }
+
+function EnqueueExternalMicrotask(fn) {
+  GetMicrotaskQueue().push(fn);
+  %SetMicrotaskPending(true);
+}

test/cctest/cctest.gyp

@@ -88,6 +88,7 @@
         'test-liveedit.cc',
         'test-lockers.cc',
         'test-log.cc',
+        'test-microtask-delivery.cc',
         'test-mark-compact.cc',
         'test-mementos.cc',
         'test-mutex.cc',

test/cctest/test-api.cc

@@ -20514,6 +20514,102 @@ TEST(CallCompletedCallbackTwoExceptions) {
 }
 
 
+static void MicrotaskOne(const v8::FunctionCallbackInfo<Value>& info) {
+  v8::HandleScope scope(info.GetIsolate());
+  CompileRun("ext1Calls++;");
+}
+
+
+static void MicrotaskTwo(const v8::FunctionCallbackInfo<Value>& info) {
+  v8::HandleScope scope(info.GetIsolate());
+  CompileRun("ext2Calls++;");
+}
+
+
+TEST(EnqueueMicrotask) {
+  LocalContext env;
+  v8::HandleScope scope(env->GetIsolate());
+  CompileRun(
+      "var ext1Calls = 0;"
+      "var ext2Calls = 0;");
+  CompileRun("1+1;");
+  CHECK_EQ(0, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(0, CompileRun("ext2Calls")->Int32Value());
+
+  v8::V8::EnqueueMicrotask(env->GetIsolate(),
+                           Function::New(env->GetIsolate(), MicrotaskOne));
+  CompileRun("1+1;");
+  CHECK_EQ(1, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(0, CompileRun("ext2Calls")->Int32Value());
+
+  v8::V8::EnqueueMicrotask(env->GetIsolate(),
+                           Function::New(env->GetIsolate(), MicrotaskOne));
+  v8::V8::EnqueueMicrotask(env->GetIsolate(),
+                           Function::New(env->GetIsolate(), MicrotaskTwo));
+  CompileRun("1+1;");
+  CHECK_EQ(2, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(1, CompileRun("ext2Calls")->Int32Value());
+
+  v8::V8::EnqueueMicrotask(env->GetIsolate(),
+                           Function::New(env->GetIsolate(), MicrotaskTwo));
+  CompileRun("1+1;");
+  CHECK_EQ(2, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(2, CompileRun("ext2Calls")->Int32Value());
+
+  CompileRun("1+1;");
+  CHECK_EQ(2, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(2, CompileRun("ext2Calls")->Int32Value());
+}
+
+
+TEST(SetAutorunMicrotasks) {
+  LocalContext env;
+  v8::HandleScope scope(env->GetIsolate());
+  CompileRun(
+      "var ext1Calls = 0;"
+      "var ext2Calls = 0;");
+  CompileRun("1+1;");
+  CHECK_EQ(0, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(0, CompileRun("ext2Calls")->Int32Value());
+
+  v8::V8::EnqueueMicrotask(env->GetIsolate(),
+                           Function::New(env->GetIsolate(), MicrotaskOne));
+  CompileRun("1+1;");
+  CHECK_EQ(1, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(0, CompileRun("ext2Calls")->Int32Value());
+
+  V8::SetAutorunMicrotasks(env->GetIsolate(), false);
+  v8::V8::EnqueueMicrotask(env->GetIsolate(),
+                           Function::New(env->GetIsolate(), MicrotaskOne));
+  v8::V8::EnqueueMicrotask(env->GetIsolate(),
+                           Function::New(env->GetIsolate(), MicrotaskTwo));
+  CompileRun("1+1;");
+  CHECK_EQ(1, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(0, CompileRun("ext2Calls")->Int32Value());
+
+  V8::RunMicrotasks(env->GetIsolate());
+  CHECK_EQ(2, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(1, CompileRun("ext2Calls")->Int32Value());
+
+  v8::V8::EnqueueMicrotask(env->GetIsolate(),
+                           Function::New(env->GetIsolate(), MicrotaskTwo));
+  CompileRun("1+1;");
+  CHECK_EQ(2, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(1, CompileRun("ext2Calls")->Int32Value());
+
+  V8::RunMicrotasks(env->GetIsolate());
+  CHECK_EQ(2, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(2, CompileRun("ext2Calls")->Int32Value());
+
+  V8::SetAutorunMicrotasks(env->GetIsolate(), true);
+  v8::V8::EnqueueMicrotask(env->GetIsolate(),
+                           Function::New(env->GetIsolate(), MicrotaskTwo));
+  CompileRun("1+1;");
+  CHECK_EQ(2, CompileRun("ext1Calls")->Int32Value());
+  CHECK_EQ(3, CompileRun("ext2Calls")->Int32Value());
+}
+
+
 static int probes_counter = 0;
 static int misses_counter = 0;
 static int updates_counter = 0;

test/cctest/test-microtask-delivery.cc

+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+
+#include "cctest.h"
+
+using namespace v8;
+namespace i = v8::internal;
+
+namespace {
+class HarmonyIsolate {
+ public:
+  HarmonyIsolate() {
+    i::FLAG_harmony_observation = true;
+    i::FLAG_harmony_promises = true;
+    isolate_ = Isolate::New();
+    isolate_->Enter();
+  }
+
+  ~HarmonyIsolate() {
+    isolate_->Exit();
+    isolate_->Dispose();
+  }
+
+  Isolate* GetIsolate() const { return isolate_; }
+
+ private:
+  Isolate* isolate_;
+};
+}
+
+
+TEST(MicrotaskDeliverySimple) {
+  HarmonyIsolate isolate;
+  HandleScope scope(isolate.GetIsolate());
+  LocalContext context(isolate.GetIsolate());
+  CompileRun(
+      "var ordering = [];"
+      "var resolver = {};"
+      "function handler(resolve) { resolver.resolve = resolve; }"
+      "var obj = {};"
+      "var observeOrders = [1, 4];"
+      "function observer() {"
+        "ordering.push(observeOrders.shift());"
+        "resolver.resolve();"
+      "}"
+      "var p = new Promise(handler);"
+      "p.then(function() {"
+        "ordering.push(2);"
+      "}).then(function() {"
+        "ordering.push(3);"
+        "obj.id++;"
+        "return new Promise(handler);"
+      "}).then(function() {"
+        "ordering.push(5);"
+      "}).then(function() {"
+        "ordering.push(6);"
+      "});"
+      "Object.observe(obj, observer);"
+      "obj.id = 1;");
+  CHECK_EQ(6, CompileRun("ordering.length")->Int32Value());
+  CHECK_EQ(1, CompileRun("ordering[0]")->Int32Value());
+  CHECK_EQ(2, CompileRun("ordering[1]")->Int32Value());
+  CHECK_EQ(3, CompileRun("ordering[2]")->Int32Value());
+  CHECK_EQ(4, CompileRun("ordering[3]")->Int32Value());
+  CHECK_EQ(5, CompileRun("ordering[4]")->Int32Value());
+  CHECK_EQ(6, CompileRun("ordering[5]")->Int32Value());
+}
+
+
+TEST(MicrotaskPerIsolateState) {
+  HarmonyIsolate isolate;
+  HandleScope scope(isolate.GetIsolate());
+  LocalContext context1(isolate.GetIsolate());
+  V8::SetAutorunMicrotasks(isolate.GetIsolate(), false);
+  CompileRun(
+      "var obj = { calls: 0 };");
+  Handle<Value> obj = CompileRun("obj");
+  {
+    LocalContext context2(isolate.GetIsolate());
+    context2->Global()->Set(String::NewFromUtf8(isolate.GetIsolate(), "obj"),
+                            obj);
+    CompileRun(
+        "var resolver = {};"
+        "new Promise(function(resolve) {"
+          "resolver.resolve = resolve;"
+        "}).then(function() {"
+          "obj.calls++;"
+        "});"
+        "(function() {"
+          "resolver.resolve();"
+        "})();");
+  }
+  {
+    LocalContext context3(isolate.GetIsolate());
+    context3->Global()->Set(String::NewFromUtf8(isolate.GetIsolate(), "obj"),
+                            obj);
+    CompileRun(
+        "var foo = { id: 1 };"
+        "Object.observe(foo, function() {"
+          "obj.calls++;"
+        "});"
+        "foo.id++;");
+  }
+  {
+    LocalContext context4(isolate.GetIsolate());
+    context4->Global()->Set(String::NewFromUtf8(isolate.GetIsolate(), "obj"),
+                            obj);
+    V8::RunMicrotasks(isolate.GetIsolate());
+    CHECK_EQ(2, CompileRun("obj.calls")->Int32Value());
+  }
+}

test/mjsunit/fuzz-natives-part3.js

@@ -216,7 +216,10 @@ var knownProblems = {
   "DataViewInitialize":true,
   "DataViewGetBuffer": true,
   "DataViewGetByteLength": true,
-  "DataViewGetByteOffset": true
+  "DataViewGetByteOffset": true,
+
+  // Only ever called internally.
+  "RunMicrotasks": true
 };
 
 var currentlyUncallable = {

test/mjsunit/harmony/microtask-delivery.js

+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --harmony-observation --harmony-promises --allow-natives-syntax
+
+var ordering = [];
+function reset() {
+  ordering = [];
+}
+
+function assertArrayValues(expected, actual) {
+  assertEquals(expected.length, actual.length);
+  for (var i = 0; i < expected.length; i++) {
+    assertEquals(expected[i], actual[i]);
+  }
+}
+
+function assertOrdering(expected) {
+  %RunMicrotasks();
+  assertArrayValues(expected, ordering);
+}
+
+function newPromise(id, fn) {
+  var r;
+  var t = 1;
+  var promise = new Promise(function(resolve) {
+    r = resolve;
+    if (fn) fn();
+  });
+
+  var next = promise.then(function(value) {
+    ordering.push('p' + id);
+    return value;
+  });
+
+  return {
+    resolve: r,
+    then: function(fn) {
+      next = next.then(function(value) {
+        ordering.push('p' + id + ':' + t++);
+        return fn ? fn(value) : value;
+      });
+
+      return this;
+    }
+  };
+}
+
+function newObserver(id, fn, obj) {
+  var observer = {
+    value: 1,
+    recordCounts: []
+  };
+
+  Object.observe(observer, function(records) {
+    ordering.push('o' + id);
+    observer.recordCounts.push(records.length);
+    if (fn) fn();
+  });
+
+  return observer;
+}
+
+
+(function PromiseThens() {
+  reset();
+
+  var p1 = newPromise(1).then();
+  var p2 = newPromise(2).then();
+
+  p1.resolve();
+  p2.resolve();
+
+  assertOrdering(['p1', 'p2', 'p1:1', 'p2:1']);
+})();
+
+
+(function ObserversBatch() {
+  reset();
+
+  var p1 = newPromise(1);
+  var p2 = newPromise(2);
+  var p3 = newPromise(3);
+
+  var ob1 = newObserver(1);
+  var ob2 = newObserver(2, function() {
+    ob3.value++;
+    p3.resolve();
+    ob1.value++;
+  });
+  var ob3 = newObserver(3);
+
+  p1.resolve();
+  ob1.value++;
+  p2.resolve();
+  ob2.value++;
+
+  assertOrdering(['p1', 'o1', 'o2', 'p2', 'o1', 'o3', 'p3']);
+  assertArrayValues([1, 1], ob1.recordCounts);
+  assertArrayValues([1], ob2.recordCounts);
+  assertArrayValues([1], ob3.recordCounts);
+})();
+
+
+(function ObserversGetAllRecords() {
+  reset();
+
+  var p1 = newPromise(1);
+  var p2 = newPromise(2);
+  var ob1 = newObserver(1, function() {
+    ob2.value++;
+  });
+  var ob2 = newObserver(2);
+
+  p1.resolve();
+  ob1.value++;
+  p2.resolve();
+  ob2.value++;
+
+  assertOrdering(['p1', 'o1', 'o2', 'p2']);
+  assertArrayValues([1], ob1.recordCounts);
+  assertArrayValues([2], ob2.recordCounts);
+})();
+
+
+(function NewObserverDeliveryGetsNewMicrotask() {
+  reset();
+
+  var p1 = newPromise(1);
+  var p2 = newPromise(2);
+  var ob1 = newObserver(1);
+  var ob2 = newObserver(2, function() {
+    ob1.value++;
+  });
+
+  p1.resolve();
+  ob1.value++;
+  p2.resolve();
+  ob2.value++;
+
+  assertOrdering(['p1', 'o1', 'o2', 'p2', 'o1']);
+  assertArrayValues([1, 1], ob1.recordCounts);
+  assertArrayValues([1], ob2.recordCounts);
+})();