n-api: make changes for source compatibility

These changes are necessary in order to retain source compatibility
with older versions of node.

The removal of `module_version` from `napi_module_register()` is
reverted from the flag removal PR, because it should not have been a
part of it.

`CallbackWrapper::NewTarget()` is renamed to
`CallbackWrapper::GetNewTarget()` to distinguish it from V8's native
method, thus allowing for a macro which reduces `NewTarget()` to
`This()` on V8 versions where it was not yet available.

`AsyncResource` is constructed with a C string rather than a V8 string
because the former is available on all versions of node.

Backport-PR-URL: #19447
PR-URL: #16102
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jason Ginchereau <jasongin@microsoft.com>

Author: Gabriel Schulhof

src/node_api.cc

@@ -461,7 +461,7 @@ class CallbackWrapper {
   CallbackWrapper(napi_value this_arg, size_t args_length, void* data)
       : _this(this_arg), _args_length(args_length), _data(data) {}
 
-  virtual napi_value NewTarget() = 0;
+  virtual napi_value GetNewTarget() = 0;
   virtual void Args(napi_value* buffer, size_t bufferlength) = 0;
   virtual void SetReturnValue(napi_value value) = 0;
 
@@ -490,7 +490,7 @@ class CallbackWrapperBase : public CallbackWrapper {
                 ->Value();
   }
 
-  napi_value NewTarget() override { return nullptr; }
+  napi_value GetNewTarget() override { return nullptr; }
 
  protected:
   void InvokeCallback() {
@@ -538,7 +538,7 @@ class FunctionCallbackWrapper
       const v8::FunctionCallbackInfo<v8::Value>& cbinfo)
       : CallbackWrapperBase(cbinfo, cbinfo.Length()) {}
 
-  napi_value NewTarget() override {
+  napi_value GetNewTarget() override {
     if (_cbinfo.IsConstructCall()) {
       return v8impl::JsValueFromV8LocalValue(_cbinfo.NewTarget());
     } else {
@@ -858,8 +858,12 @@ void napi_module_register_cb(v8::Local<v8::Object> exports,
 
 // Registers a NAPI module.
 void napi_module_register(napi_module* mod) {
+  int module_version = -1;
+#ifdef EXTERNAL_NAPI
+  module_version = NODE_MODULE_VERSION;
+#endif  // EXTERNAL_NAPI
   node::node_module* nm = new node::node_module {
-    -1,
+    module_version,
     mod->nm_flags,
     nullptr,
     mod->nm_filename,
@@ -1912,7 +1916,7 @@ napi_status napi_get_new_target(napi_env env,
   v8impl::CallbackWrapper* info =
       reinterpret_cast<v8impl::CallbackWrapper*>(cbinfo);
 
-  *result = info->NewTarget();
+  *result = info->GetNewTarget();
   return napi_clear_last_error(env);
 }
 
@@ -3339,7 +3343,7 @@ class Work : public node::AsyncResource {
                 void* data = nullptr)
     : AsyncResource(env->isolate,
                     async_resource,
-                    async_resource_name),
+                    *v8::String::Utf8Value(async_resource_name)),
     _env(env),
     _data(data),
     _execute(execute),

src/node_api_backport.cc

@@ -73,7 +73,7 @@ CallbackScope::~CallbackScope() {
 
 AsyncResource::AsyncResource(v8::Isolate* _isolate,
                              v8::Local<v8::Object> _object,
-                             v8::Local<v8::String> name) : isolate(_isolate) {
+                             char* name) : isolate(_isolate) {
   object.Reset(isolate, _object);
 }
 

src/node_api_backport.h

@@ -50,7 +50,7 @@ class AsyncResource {
  public:
   AsyncResource(v8::Isolate* _isolate,
                 v8::Local<v8::Object> _object,
-                v8::Local<v8::String> name);
+                char* name);
   ~AsyncResource();
   v8::Isolate* isolate;
   v8::Persistent<v8::Object> object;