src: make ReqWrap weak

This commit allows throwing an exception after creating `FSReqCallback`

lib/fs.js

@@ -24,10 +24,6 @@
 
 'use strict';
 
-// When using FSReqCallback, make sure to create the object only *after* all
-// parameter validation has happened, so that the objects are not kept in memory
-// in case they are created but never used due to an exception.
-
 const {
   ArrayPrototypePush,
   BigIntPrototypeToString,

src/req_wrap-inl.h

@@ -20,12 +20,12 @@ ReqWrap<T>::ReqWrap(Environment* env,
                     AsyncWrap::ProviderType provider)
     : AsyncWrap(env, object, provider),
       ReqWrapBase(env) {
+  MakeWeak();
   Reset();
 }
 
 template <typename T>
 ReqWrap<T>::~ReqWrap() {
-  CHECK_EQ(false, persistent().IsEmpty());
 }
 
 template <typename T>
@@ -138,7 +138,6 @@ template <typename T>
 template <typename LibuvFunction, typename... Args>
 int ReqWrap<T>::Dispatch(LibuvFunction fn, Args... args) {
   Dispatched();
-
   // This expands as:
   //
   // int err = fn(env()->event_loop(), req(), arg1, arg2, Wrapper, arg3, ...)
@@ -158,8 +157,10 @@ int ReqWrap<T>::Dispatch(LibuvFunction fn, Args... args) {
       env()->event_loop(),
       req(),
       MakeLibuvRequestCallback<T, Args>::For(this, args)...);
-  if (err >= 0)
+  if (err >= 0) {
+    ClearWeak();
     env()->IncreaseWaitingRequestCounter();
+  }
   return err;
 }