Bug 966471. Add some facilities for examining the state of a promise via a PromiseDebugging utility namespace. r=nsm,peterv

dom/bindings/Bindings.conf

@@ -997,6 +997,10 @@ DOMInterfaces = {
     'implicitJSContext': [ 'then', 'catch' ],
 },
 
+'PromiseDebugging': {
+    'concrete': False,
+},
+
 'PropertyNodeList': {
     'headerFile': 'HTMLPropertiesCollection.h',
     'resultNotAddRefed': [ 'item' ]

dom/promise/Promise.h

@@ -30,6 +30,7 @@ class DOMError;
 class PromiseCallback;
 class PromiseInit;
 class PromiseNativeHandler;
+class PromiseDebugging;
 
 class Promise;
 class PromiseReportRejectFeature : public workers::WorkerFeature
@@ -154,6 +155,8 @@ public:
   void AppendNativeHandler(PromiseNativeHandler* aRunnable);
 
 private:
+  friend class PromiseDebugging;
+
   enum PromiseState {
     Pending,
     Resolved,

dom/promise/PromiseDebugging.cpp

@@ -0,0 +1,40 @@
+/* -*- Mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 40 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/PromiseDebugging.h"
+
+#include "js/Value.h"
+
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/PromiseDebuggingBinding.h"
+
+namespace mozilla {
+namespace dom {
+
+/* static */ void
+PromiseDebugging::GetState(GlobalObject&, Promise& aPromise,
+                           PromiseDebuggingStateHolder& aState)
+{
+  switch (aPromise.mState) {
+  case Promise::Pending:
+    aState.mState = PromiseDebuggingState::Pending;
+    break;
+  case Promise::Resolved:
+    aState.mState = PromiseDebuggingState::Fulfilled;
+    JS::ExposeValueToActiveJS(aPromise.mResult);
+    aState.mValue = aPromise.mResult;
+    break;
+  case Promise::Rejected:
+    aState.mState = PromiseDebuggingState::Rejected;
+    JS::ExposeValueToActiveJS(aPromise.mResult);
+    aState.mReason = aPromise.mResult;
+    break;
+  }
+}
+
+} // namespace dom
+} // namespace mozilla

dom/promise/PromiseDebugging.h

@@ -0,0 +1,27 @@
+/* -*- Mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 40 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_PromiseDebugging_h
+#define mozilla_dom_PromiseDebugging_h
+
+namespace mozilla {
+namespace dom {
+
+class Promise;
+struct PromiseDebuggingStateHolder;
+class GlobalObject;
+
+class PromiseDebugging
+{
+public:
+  static void GetState(GlobalObject&, Promise& aPromise,
+                       PromiseDebuggingStateHolder& aState);
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif // mozilla_dom_PromiseDebugging_h

dom/promise/moz.build

@@ -8,13 +8,15 @@ TEST_DIRS += ['tests']
 
 EXPORTS.mozilla.dom += [
     'Promise.h',
+    'PromiseDebugging.h',
     'PromiseNativeHandler.h',
     'PromiseWorkerProxy.h',
 ]
 
-SOURCES += [
+UNIFIED_SOURCES += [
     'Promise.cpp',
     'PromiseCallback.cpp',
+    'PromiseDebugging.cpp'
 ]
 
 FAIL_ON_WARNINGS = True

dom/webidl/PromiseDebugging.webidl

@@ -0,0 +1,20 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+/* This is a utility namespace for promise-debugging functionality */
+
+
+dictionary PromiseDebuggingStateHolder {
+  PromiseDebuggingState state = "pending";
+  any value;
+  any reason;
+};
+enum PromiseDebuggingState { "pending", "fulfilled", "rejected" };
+
+[ChromeOnly]
+interface PromiseDebugging {
+  static PromiseDebuggingStateHolder getState(Promise p);
+};

dom/webidl/moz.build

@@ -297,6 +297,7 @@ WEBIDL_FILES = [
     'PositionError.webidl',
     'ProcessingInstruction.webidl',
     'Promise.webidl',
+    'PromiseDebugging.webidl',
     'PushManager.webidl',
     'Range.webidl',
     'Rect.webidl',