refactor(napi): simplify napi_value interface (#16170)

cli/napi/js_native_api.rs

@@ -23,6 +23,14 @@ macro_rules! check_arg {
   };
 }
 
+macro_rules! check_arg_option {
+  ($ptr: expr) => {
+    if $ptr.is_none() {
+      return Err(Error::InvalidArg);
+    }
+  };
+}
+
 /// Returns napi_value that represents a new JavaScript Array.
 #[napi_sym::napi_sym]
 fn napi_create_array(env: *mut Env, result: *mut napi_value) -> Result {
@@ -30,7 +38,7 @@ fn napi_create_array(env: *mut Env, result: *mut napi_value) -> Result {
   check_arg!(result);
 
   let value = v8::Array::new(&mut env.scope(), 0);
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value.into());
+  *result = value.into();
   Ok(())
 }
 
@@ -44,7 +52,7 @@ fn napi_create_array_with_length(
   check_arg!(result);
 
   let value = v8::Array::new(&mut env.scope(), len);
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value.into());
+  *result = value.into();
   Ok(())
 }
 
@@ -63,7 +71,7 @@ fn napi_create_arraybuffer(
     *data = get_array_buffer_ptr(value);
   }
 
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value.into());
+  *result = value.into();
   Ok(())
 }
 
@@ -77,7 +85,7 @@ fn napi_create_bigint_int64(
   check_arg!(result);
 
   let value = v8::BigInt::new_from_i64(&mut env.scope(), value);
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value.into());
+  *result = value.into();
   Ok(())
 }
 
@@ -90,7 +98,7 @@ fn napi_create_bigint_uint64(
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
   let value: v8::Local<v8::Value> =
     v8::BigInt::new_from_u64(&mut env.scope(), value).into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -110,7 +118,7 @@ fn napi_create_bigint_words(
   )
   .unwrap()
   .into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -128,7 +136,7 @@ fn napi_create_buffer(
   }
   let value = v8::Uint8Array::new(&mut env.scope(), value, 0, len).unwrap();
   let value: v8::Local<v8::Value> = value.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -149,7 +157,7 @@ fn napi_create_buffer_copy(
   }
   let value = v8::Uint8Array::new(&mut env.scope(), value, 0, len).unwrap();
   let value: v8::Local<v8::Value> = value.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -163,7 +171,7 @@ fn napi_coerce_to_bool(
   let value = transmute::<napi_value, v8::Local<v8::Value>>(value);
   let coerced = value.to_boolean(&mut env.scope());
   let value: v8::Local<v8::Value> = coerced.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -179,7 +187,7 @@ fn napi_coerce_to_number(
     .to_number(&mut env.scope())
     .ok_or(Error::NumberExpected)?;
   let value: v8::Local<v8::Value> = coerced.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -193,7 +201,7 @@ fn napi_coerce_to_object(
   let value = transmute::<napi_value, v8::Local<v8::Value>>(value);
   let coerced = value.to_object(&mut env.scope()).unwrap();
   let value: v8::Local<v8::Value> = coerced.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -207,7 +215,7 @@ fn napi_coerce_to_string(
   let value = transmute::<napi_value, v8::Local<v8::Value>>(value);
   let coerced = value.to_string(&mut env.scope()).unwrap();
   let value: v8::Local<v8::Value> = coerced.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -240,7 +248,7 @@ fn napi_create_dataview(
     )
     .unwrap();
   let value: v8::Local<v8::Value> = value.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -253,7 +261,7 @@ fn napi_create_date(
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
   let value: v8::Local<v8::Value> =
     v8::Date::new(&mut env.scope(), time).unwrap().into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -266,7 +274,7 @@ fn napi_create_double(
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
   let value: v8::Local<v8::Value> =
     v8::Number::new(&mut env.scope(), value).into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -285,7 +293,7 @@ fn napi_create_error(
   let msg = msg.to_string(&mut env.scope()).unwrap();
 
   let error = v8::Exception::error(&mut env.scope(), msg);
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(error);
+  *result = error.into();
 
   Ok(())
 }
@@ -302,7 +310,7 @@ fn napi_create_external(
   let value: v8::Local<v8::Value> =
     v8::External::new(&mut env.scope(), value).into();
   // TODO: finalization
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -353,7 +361,7 @@ fn napi_create_external_arraybuffer(
   let ab =
     v8::ArrayBuffer::with_backing_store(&mut env.scope(), &store.make_shared());
   let value: v8::Local<v8::Value> = ab.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -382,7 +390,7 @@ fn napi_create_external_buffer(
   let value =
     v8::Uint8Array::new(&mut env.scope(), ab, 0, slice.len()).unwrap();
   let value: v8::Local<v8::Value> = value.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -416,7 +424,7 @@ fn napi_create_function(
 
   let function = create_function(env_ptr, name, cb, cb_info);
   let value: v8::Local<v8::Value> = function.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -429,7 +437,7 @@ fn napi_create_int32(
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
   let value: v8::Local<v8::Value> =
     v8::Number::new(&mut env.scope(), value as f64).into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -442,7 +450,7 @@ fn napi_create_int64(
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
   let value: v8::Local<v8::Value> =
     v8::Number::new(&mut env.scope(), value as f64).into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -450,7 +458,7 @@ fn napi_create_int64(
 fn napi_create_object(env: *mut Env, result: *mut napi_value) -> Result {
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
   let object = v8::Object::new(&mut env.scope());
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(object.into());
+  *result = object.into();
   Ok(())
 }
 
@@ -466,7 +474,7 @@ fn napi_create_promise(
   let mut global_ptr = global.into_raw();
   let promise = resolver.get_promise(&mut env.scope());
   *deferred = global_ptr.as_mut() as *mut _ as napi_deferred;
-  *promise_out = transmute::<v8::Local<v8::Value>, napi_value>(promise.into());
+  *promise_out = promise.into();
 
   Ok(())
 }
@@ -486,7 +494,7 @@ fn napi_create_range_error(
   let msg = msg.to_string(&mut env.scope()).unwrap();
 
   let error = v8::Exception::range_error(&mut env.scope(), msg);
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(error);
+  *result = error.into();
 
   Ok(())
 }
@@ -531,7 +539,7 @@ fn napi_create_string_latin1(
   ) {
     Some(v8str) => {
       let value: v8::Local<v8::Value> = v8str.into();
-      *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+      *result = value.into();
     }
     None => return Err(Error::GenericFailure),
   }
@@ -555,7 +563,7 @@ fn napi_create_string_utf16(
   )
   .unwrap();
   let value: v8::Local<v8::Value> = v8str.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -578,7 +586,7 @@ fn napi_create_string_utf8(
   };
   let v8str = v8::String::new(&mut env.scope(), string).unwrap();
   let value: v8::Local<v8::Value> = v8str.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
 
   Ok(())
 }
@@ -590,7 +598,7 @@ fn napi_create_symbol(
   result: *mut napi_value,
 ) -> Result {
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
-  let description = match description.is_null() {
+  let description = match description.is_none() {
     true => None,
     false => Some(
       transmute::<napi_value, v8::Local<v8::Value>>(description)
@@ -599,7 +607,7 @@ fn napi_create_symbol(
     ),
   };
   let sym = v8::Symbol::new(&mut env.scope(), description);
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(sym.into());
+  *result = sym.into();
   Ok(())
 }
 
@@ -618,7 +626,7 @@ fn napi_create_type_error(
   let msg = msg.to_string(&mut env.scope()).unwrap();
 
   let error = v8::Exception::type_error(&mut env.scope(), msg);
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(error);
+  *result = error.into();
 
   Ok(())
 }
@@ -695,7 +703,7 @@ fn napi_create_typedarray(
       return Err(Error::InvalidArg);
     }
   };
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(typedarray);
+  *result = typedarray.into();
   Ok(())
 }
 
@@ -708,7 +716,7 @@ fn napi_create_uint32(
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
   let value: v8::Local<v8::Value> =
     v8::Number::new(&mut env.scope(), value as f64).into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -723,7 +731,7 @@ fn napi_make_callback(
   result: *mut napi_value,
 ) -> Result {
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
-  check_arg!(recv);
+  check_arg_option!(recv);
   if argc > 0 {
     check_arg!(argv);
   }
@@ -1172,7 +1180,7 @@ fn napi_define_class(
   }
 
   let value: v8::Local<v8::Value> = tpl.get_function(scope).unwrap().into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1260,11 +1268,11 @@ fn napi_detach_arraybuffer(_env: *mut Env, value: napi_value) -> Result {
 }
 
 #[napi_sym::napi_sym]
-fn napi_escape_handle(
+fn napi_escape_handle<'s>(
   _env: *mut Env,
   _handle_scope: napi_escapable_handle_scope,
-  escapee: napi_value,
-  result: *mut napi_value,
+  escapee: napi_value<'s>,
+  result: *mut napi_value<'s>,
 ) -> Result {
   // TODO
   *result = escapee;
@@ -1286,7 +1294,7 @@ fn napi_get_and_clear_last_exception(
   // TODO: just return undefined for now we don't cache
   // exceptions in env.
   let value: v8::Local<v8::Value> = v8::undefined(&mut env.scope()).into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1326,7 +1334,7 @@ fn napi_get_boolean(
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
   let value: v8::Local<v8::Value> =
     v8::Boolean::new(&mut env.scope(), value).into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1370,7 +1378,7 @@ fn napi_get_cb_info(
 
   if !this_arg.is_null() {
     let mut this = args.this();
-    *this_arg = transmute::<v8::Local<v8::Value>, napi_value>(this.into());
+    *this_arg = this.into();
   }
 
   let len = args.length();
@@ -1383,7 +1391,7 @@ fn napi_get_cb_info(
     let mut v_argv = std::slice::from_raw_parts_mut(argv, v_argc as usize);
     for i in 0..v_argc {
       let mut arg = args.get(i);
-      v_argv[i as usize] = transmute::<v8::Local<v8::Value>, napi_value>(arg);
+      v_argv[i as usize] = arg.into();
     }
   }
 
@@ -1437,7 +1445,7 @@ fn napi_get_element(
   let array = v8::Local::<v8::Array>::try_from(object).unwrap();
   let value: v8::Local<v8::Value> =
     array.get_index(&mut env.scope(), index).unwrap();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1448,7 +1456,7 @@ fn napi_get_global(env: *mut Env, result: *mut napi_value) -> Result {
   let context = &mut env.scope().get_current_context();
   let global = context.global(&mut env.scope());
   let value: v8::Local<v8::Value> = global.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1493,7 +1501,7 @@ fn napi_get_named_property(
     .unwrap()
     .get(&mut env.scope(), name.into())
     .unwrap();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1513,7 +1521,7 @@ fn napi_get_null(env: *mut Env, result: *mut napi_value) -> Result {
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
 
   let value: v8::Local<v8::Value> = v8::null(&mut env.scope()).into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1528,7 +1536,7 @@ fn napi_get_property(
   let object = transmute::<napi_value, v8::Local<v8::Object>>(object);
   let key = transmute::<napi_value, v8::Local<v8::Value>>(key);
   let value: v8::Local<v8::Value> = object.get(&mut env.scope(), key).unwrap();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1546,7 +1554,7 @@ fn napi_get_property_names(
     .get_property_names(&mut env.scope(), Default::default())
     .unwrap();
   let value: v8::Local<v8::Value> = array.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1560,7 +1568,7 @@ fn napi_get_prototype(
   let value = transmute::<napi_value, v8::Local<v8::Value>>(value);
   let obj = value.to_object(&mut env.scope()).unwrap();
   let proto = obj.get_prototype(&mut env.scope()).unwrap();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(proto);
+  *result = proto.into();
   Ok(())
 }
 
@@ -1574,7 +1582,7 @@ fn napi_get_reference_value(
   let _env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
 
   let value = transmute::<napi_ref, v8::Local<v8::Value>>(reference);
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1604,7 +1612,7 @@ fn napi_get_typedarray_info(
 fn napi_get_undefined(env: *mut Env, result: *mut napi_value) -> Result {
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
   let value: v8::Local<v8::Value> = v8::undefined(&mut env.scope()).into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -1704,8 +1712,8 @@ fn napi_instanceof(
   result: *mut bool,
 ) -> Result {
   let env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
-  check_arg!(constructor);
-  check_arg!(value);
+  check_arg_option!(constructor);
+  check_arg_option!(value);
 
   let value = transmute::<napi_value, v8::Local<v8::Value>>(value);
   let constructor = transmute::<napi_value, v8::Local<v8::Value>>(constructor);
@@ -1853,7 +1861,7 @@ fn napi_new_instance(
     transmute(std::slice::from_raw_parts(argv, argc));
   let inst = constructor.new_instance(&mut env.scope(), args).unwrap();
   let value: v8::Local<v8::Value> = inst.into();
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(value);
+  *result = value.into();
   Ok(())
 }
 
@@ -2000,7 +2008,7 @@ fn napi_run_script(
   let rv = script.run(&mut env.scope());
 
   if let Some(rv) = rv {
-    *result = transmute::<v8::Local<v8::Value>, napi_value>(rv);
+    *result = rv.into();
   } else {
     return Err(Error::GenericFailure);
   }
@@ -2187,7 +2195,7 @@ fn napi_typeof(
   value: napi_value,
   result: *mut napi_valuetype,
 ) -> Result {
-  if value.is_null() {
+  if value.is_none() {
     *result = napi_undefined;
     return Ok(());
   }
@@ -2269,7 +2277,7 @@ fn node_api_create_syntax_error(
   let msg = msg.to_string(&mut env.scope()).unwrap();
 
   let error = v8::Exception::syntax_error(&mut env.scope(), msg);
-  *result = transmute::<v8::Local<v8::Value>, napi_value>(error);
+  *result = error.into();
 
   Ok(())
 }

cli/napi/threadsafe_functions.rs

@@ -49,22 +49,12 @@ impl TsFn {
             let func: v8::Local<v8::Value> =
               func.open(scope).to_object(scope).unwrap().into();
             unsafe {
-              call_js_cb(
-                env as *mut c_void,
-                transmute::<v8::Local<v8::Value>, napi_value>(func),
-                context,
-                data,
-              )
+              call_js_cb(env as *mut c_void, func.into(), context, data)
             };
           }
           None => {
             unsafe {
-              call_js_cb(
-                env as *mut c_void,
-                std::ptr::null_mut(),
-                context,
-                data,
-              )
+              call_js_cb(env as *mut c_void, std::mem::zeroed(), context, data)
             };
           }
         }
@@ -110,9 +100,7 @@ fn napi_create_threadsafe_function(
     return Err(Error::InvalidArg);
   }
   let maybe_func = func
-    .as_mut()
-    .map(|func| {
-      let value = transmute::<napi_value, v8::Local<v8::Value>>(func);
+    .map(|value| {
       let func = v8::Local::<v8::Function>::try_from(value)
         .map_err(|_| Error::FunctionExpected)?;
       Ok(v8::Global::new(&mut env_ref.scope(), func))

cli/napi_sym/lib.rs

@@ -27,6 +27,7 @@ pub fn napi_sym(_attr: TokenStream, item: TokenStream) -> TokenStream {
   let block = &func.block;
   let inputs = &func.sig.inputs;
   let output = &func.sig.output;
+  let generics = &func.sig.generics;
   let ret_ty = match output {
     syn::ReturnType::Default => panic!("expected a return type"),
     syn::ReturnType::Type(_, ty) => quote! { #ty },
@@ -34,7 +35,7 @@ pub fn napi_sym(_attr: TokenStream, item: TokenStream) -> TokenStream {
   TokenStream::from(quote! {
       // SAFETY: it's an NAPI function.
       #[no_mangle]
-      pub unsafe extern "C" fn #name(#inputs) -> napi_status {
+      pub unsafe extern "C" fn #name #generics (#inputs) -> napi_status {
         let mut inner = || -> #ret_ty {
           #block
         };

ext/napi/lib.rs

@@ -12,18 +12,12 @@ use deno_core::futures::channel::mpsc;
 use deno_core::futures::StreamExt;
 use deno_core::op;
 use deno_core::serde_v8;
-pub use deno_core::v8;
 use deno_core::Extension;
 use deno_core::OpState;
 use std::cell::RefCell;
-pub use std::ffi::CStr;
 use std::ffi::CString;
-pub use std::mem::transmute;
-pub use std::os::raw::c_char;
-pub use std::os::raw::c_void;
 use std::path::Path;
 use std::path::PathBuf;
-pub use std::ptr;
 use std::task::Poll;
 use std::thread_local;
 
@@ -33,11 +27,21 @@ use libloading::os::unix::*;
 #[cfg(windows)]
 use libloading::os::windows::*;
 
+// Expose common stuff for ease of use.
+// `use deno_napi::*`
+pub use deno_core::v8;
+pub use std::ffi::CStr;
+pub use std::mem::transmute;
+pub use std::os::raw::c_char;
+pub use std::os::raw::c_void;
+pub use std::ptr;
+pub use value::napi_value;
+
 pub mod function;
+mod value;
 
 pub type napi_status = i32;
 pub type napi_env = *mut c_void;
-pub type napi_value = *mut c_void;
 pub type napi_callback_info = *mut c_void;
 pub type napi_deferred = *mut c_void;
 pub type napi_ref = *mut c_void;
@@ -81,7 +85,7 @@ type napi_addon_register_func =
   extern "C" fn(env: napi_env, exports: napi_value) -> napi_value;
 
 #[repr(C)]
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct NapiModule {
   pub nm_version: i32,
   pub nm_flags: u32,
@@ -211,7 +215,10 @@ pub struct napi_type_tag {
 }
 
 pub type napi_callback = Option<
-  unsafe extern "C" fn(env: napi_env, info: napi_callback_info) -> napi_value,
+  unsafe extern "C" fn(
+    env: napi_env,
+    info: napi_callback_info,
+  ) -> napi_value<'static>,
 >;
 
 pub type napi_finalize = unsafe extern "C" fn(
@@ -250,13 +257,13 @@ pub const napi_default_jsproperty: napi_property_attributes =
 
 #[repr(C)]
 #[derive(Copy, Clone, Debug)]
-pub struct napi_property_descriptor {
+pub struct napi_property_descriptor<'a> {
   pub utf8name: *const c_char,
-  pub name: napi_value,
+  pub name: napi_value<'a>,
   pub method: napi_callback,
   pub getter: napi_callback,
   pub setter: napi_callback,
-  pub value: napi_value,
+  pub value: napi_value<'a>,
   pub attributes: napi_property_attributes,
   pub data: *mut c_void,
 }

ext/napi/value.rs

@@ -0,0 +1,58 @@
+// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
+
+use deno_core::v8;
+use std::mem::transmute;
+use std::ops::Deref;
+use std::os::raw::c_void;
+use std::ptr::NonNull;
+
+/// An FFI-opaque, nullable wrapper around v8::Local<v8::Value>.
+/// rusty_v8 Local handle cannot be empty but napi_value can be.
+#[repr(transparent)]
+#[derive(Clone, Copy, Debug)]
+pub struct NapiValue<'s>(
+  Option<NonNull<v8::Value>>,
+  std::marker::PhantomData<&'s ()>,
+);
+
+pub type napi_value<'s> = NapiValue<'s>;
+
+impl<'s> Deref for napi_value<'s> {
+  type Target = Option<v8::Local<'s, v8::Value>>;
+  fn deref(&self) -> &Self::Target {
+    // SAFETY: It is safe to transmute `Option<NonNull<T>>` to `Option<*const T>`.
+    //         v8::Local guarantees that *const T is not null but napi_value *can* be null.
+    unsafe { transmute::<&Self, &Self::Target>(self) }
+  }
+}
+
+impl<'s, T> From<v8::Local<'s, T>> for napi_value<'s>
+where
+  v8::Local<'s, T>: Into<v8::Local<'s, v8::Value>>,
+{
+  fn from(v: v8::Local<'s, T>) -> Self {
+    // SAFETY: It is safe to cast v8::Local<T> that implements Into<v8::Local<v8::Value>>.
+    //         `fn into(self)` transmutes anyways.
+    Self(unsafe { transmute(v) }, std::marker::PhantomData)
+  }
+}
+
+const _: () = {
+  assert!(
+    std::mem::size_of::<napi_value>() == std::mem::size_of::<*mut c_void>()
+  );
+  // Assert "nullable pointer optimization" on napi_value
+  unsafe {
+    type Src<'a> = napi_value<'a>;
+    type Dst = usize;
+    assert!(std::mem::size_of::<Src>() == std::mem::size_of::<Dst>());
+    union Transmute<'a> {
+      src: Src<'a>,
+      dst: Dst,
+    }
+    Transmute {
+      src: NapiValue(None, std::marker::PhantomData),
+    }
+    .dst
+  };
+};