Make it possible for a Runtime to provide its own JSON parsing

Summary: Make it possible for a Runtime implementation to provide its own JSON parsing, by making the method on Value call through Runtime, which now has the default implementation.

Reviewed By: tmikov

Differential Revision: D17637395

fbshipit-source-id: b8997f7d1721a7790326417f3abfa86c875923c9

ReactCommon/jsi/jsi/jsi.cpp

@@ -102,6 +102,13 @@ Instrumentation& Runtime::instrumentation() {
   return sharedInstance;
 }
 
+Value Runtime::createValueFromJsonUtf8(const uint8_t* json, size_t length) {
+  Function parseJson = global()
+                           .getPropertyAsObject(*this, "JSON")
+                           .getPropertyAsFunction(*this, "parse");
+  return parseJson.call(*this, String::createFromUtf8(*this, json, length));
+}
+
 Pointer& Pointer::operator=(Pointer&& other) {
   if (ptr_) {
     ptr_->invalidate();
@@ -214,16 +221,6 @@ Value::~Value() {
   }
 }
 
-Value Value::createFromJsonUtf8(
-    Runtime& runtime,
-    const uint8_t* json,
-    size_t length) {
-  Function parseJson = runtime.global()
-                           .getPropertyAsObject(runtime, "JSON")
-                           .getPropertyAsFunction(runtime, "parse");
-  return parseJson.call(runtime, String::createFromUtf8(runtime, json, length));
-}
-
 bool Value::strictEquals(Runtime& runtime, const Value& a, const Value& b) {
   if (a.kind_ != b.kind_) {
     return false;

ReactCommon/jsi/jsi/jsi.h

@@ -252,6 +252,10 @@ class Runtime {
   virtual String createStringFromUtf8(const uint8_t* utf8, size_t length) = 0;
   virtual std::string utf8(const String&) = 0;
 
+  // \return a \c Value created from a utf8-encoded JSON string. The default
+  // implementation creates a \c String and invokes JSON.parse.
+  virtual Value createValueFromJsonUtf8(const uint8_t* json, size_t length);
+
   virtual Object createObject() = 0;
   virtual Object createObject(std::shared_ptr<HostObject> ho) = 0;
   virtual std::shared_ptr<HostObject> getHostObject(const jsi::Object&) = 0;
@@ -974,7 +978,9 @@ class Value {
 
   // \return a \c Value created from a utf8-encoded JSON string.
   static Value
-  createFromJsonUtf8(Runtime& runtime, const uint8_t* json, size_t length);
+  createFromJsonUtf8(Runtime& runtime, const uint8_t* json, size_t length) {
+    return runtime.createValueFromJsonUtf8(json, length);
+  }
 
   /// \return according to the SameValue algorithm see more here:
   //  https://www.ecma-international.org/ecma-262/5.1/#sec-11.9.4