src: do proper StringBytes error handling

- Return `MaybeLocal`s from `StringBytes::Encode`
- Add an `error` out parameter to pass JS exceptions to the callers
  (instead of directly throwing)
- Simplify some of the string generation methods in `string_bytes.cc`
  by unifying the `EXTERN_APEX` logic
- Reduce usage of deprecated V8 APIs.
- Remove error handling logic from JS, the `buffer.*Slice()` methods
  now throw errors themselves.
- Left TODO comments for future semver-major error message
  improvements.

This paves the way for better error messages coming out of the
StringBytes methods.

Ref: https://github.com/nodejs/node/issues/3175
PR-URL: https://github.com/nodejs/node/pull/12765
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

1 files changed, 28 insertions, 4 deletions

diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index e8d4945194..367af6592f 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -465,14 +465,26 @@ void StringSlice(const FunctionCallbackInfo<Value>& args) {
 
   SLICE_START_END(args[0], args[1], ts_obj_length)
 
-  args.GetReturnValue().Set(
-      StringBytes::Encode(isolate, ts_obj_data + start, length, encoding));
+  Local<Value> error;
+  MaybeLocal<Value> ret =
+      StringBytes::Encode(isolate,
+                          ts_obj_data + start,
+                          length,
+                          encoding,
+                          &error);
+  if (ret.IsEmpty()) {
+    CHECK(!error.IsEmpty());
+    isolate->ThrowException(error);
+    return;
+  }
+  args.GetReturnValue().Set(ret.ToLocalChecked());
 }
 
 
 template <>
 void StringSlice<UCS2>(const FunctionCallbackInfo<Value>& args) {
-  Environment* env = Environment::GetCurrent(args);
+  Isolate* isolate = args.GetIsolate();
+  Environment* env = Environment::GetCurrent(isolate);
 
   THROW_AND_RETURN_UNLESS_BUFFER(env, args.This());
   SPREAD_BUFFER_ARG(args.This(), ts_obj);
@@ -509,10 +521,22 @@ void StringSlice<UCS2>(const FunctionCallbackInfo<Value>& args) {
     buf = reinterpret_cast<const uint16_t*>(data);
   }
 
-  args.GetReturnValue().Set(StringBytes::Encode(env->isolate(), buf, length));
+  Local<Value> error;
+  MaybeLocal<Value> ret =
+      StringBytes::Encode(isolate,
+                          buf,
+                          length,
+                          &error);
 
   if (release)
     delete[] buf;
+
+  if (ret.IsEmpty()) {
+    CHECK(!error.IsEmpty());
+    isolate->ThrowException(error);
+    return;
+  }
+  args.GetReturnValue().Set(ret.ToLocalChecked());
 }