Bug 1480673 - Add nsContentUtils::StringifyJSON. r=qdot

Add nsContentUtils::StringifyJSON.

Differential Revision: https://phabricator.services.mozilla.com/D2700

--HG--
extra : moz-landing-system : lando

dom/base/nsContentUtils.cpp

@@ -11141,3 +11141,25 @@ nsContentUtils::CanShowPopup(nsIPrincipal* aPrincipal)
 
   return !sDisablePopups;
 }
+
+static bool
+JSONCreator(const char16_t* aBuf, uint32_t aLen, void* aData)
+{
+  nsAString* result = static_cast<nsAString*>(aData);
+  result->Append(static_cast<const char16_t*>(aBuf),
+                 static_cast<uint32_t>(aLen));
+  return true;
+}
+
+/* static */ bool
+nsContentUtils::StringifyJSON(JSContext* aCx, JS::MutableHandle<JS::Value> aValue, nsAString& aOutStr)
+{
+  MOZ_ASSERT(aCx);
+  aOutStr.Truncate();
+  JS::RootedValue value(aCx, aValue.get());
+  nsAutoString serializedValue;
+  NS_ENSURE_TRUE(JS_Stringify(aCx, &value, nullptr, JS::NullHandleValue,
+                              JSONCreator, &serializedValue), false);
+  aOutStr = serializedValue;
+  return true;
+}

dom/base/nsContentUtils.h

@@ -3275,6 +3275,15 @@ public:
 
   static bool CanShowPopup(nsIPrincipal* aPrincipal);
 
+  /**
+   * Serializes a JSON-like JS::Value into a string.
+   *
+   * Usage:
+   *   nsAutoString serializedValue;
+   *   nsContentUtils::StringifyJSON(cx, &value, serializedValue);
+   */
+  static bool StringifyJSON(JSContext* aCx, JS::MutableHandle<JS::Value> vp, nsAString& aOutStr);
+
 private:
   static bool InitializeEventTable();
 

dom/base/test/gtest/TestContentUtils.cpp

@@ -0,0 +1,46 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=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 "gtest/gtest.h"
+
+#include "jsapi.h"
+#include "nsContentUtils.h"
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/dom/SimpleGlobalObject.h"
+
+TEST(DOM_Base_ContentUtils, StringifyJSON_EmptyValue)
+{
+  JSObject* globalObject =
+    mozilla::dom::SimpleGlobalObject::Create(mozilla::dom::SimpleGlobalObject::GlobalType::BindingDetail);
+  mozilla::dom::AutoJSAPI jsAPI;
+  ASSERT_TRUE(jsAPI.Init(globalObject));
+  JSContext* cx = jsAPI.cx();
+  nsAutoString serializedValue;
+
+  JS::RootedValue jsValue(cx);
+  ASSERT_TRUE(nsContentUtils::StringifyJSON(cx, &jsValue, serializedValue));
+
+  ASSERT_TRUE(serializedValue.EqualsLiteral("null"));
+}
+
+TEST(DOM_Base_ContentUtils, StringifyJSON_Object)
+{
+  JSObject* globalObject =
+    mozilla::dom::SimpleGlobalObject::Create(mozilla::dom::SimpleGlobalObject::GlobalType::BindingDetail);
+  mozilla::dom::AutoJSAPI jsAPI;
+  ASSERT_TRUE(jsAPI.Init(globalObject));
+  JSContext* cx = jsAPI.cx();
+  nsAutoString serializedValue;
+
+  JS::RootedObject jsObj(cx, JS_NewPlainObject(cx));
+  JS::RootedString valueStr(cx, JS_NewStringCopyZ(cx, "Hello World!"));
+  ASSERT_TRUE(JS_DefineProperty(cx, jsObj, "key1", valueStr, JSPROP_ENUMERATE));
+  JS::RootedValue jsValue(cx, JS::ObjectValue(*jsObj));
+
+  ASSERT_TRUE(nsContentUtils::StringifyJSON(cx, &jsValue, serializedValue));
+
+  ASSERT_TRUE(serializedValue.EqualsLiteral("{\"key1\":\"Hello World!\"}"));
+}

dom/base/test/gtest/moz.build

@@ -5,6 +5,7 @@
 # file, you can obtain one at http://mozilla.org/MPL/2.0/.
 
 UNIFIED_SOURCES += [
+    'TestContentUtils.cpp',
     'TestPlainTextSerializer.cpp',
     'TestXPathGenerator.cpp',
 ]