Fix missing cases of empty_string canonicalization

src/api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 6705 matching lines @@
 MaybeLocal<String> v8::String::NewExternalTwoByte(
     Isolate* isolate, v8::String::ExternalStringResource* resource) {
   CHECK(resource && resource->data());
   // TODO(dcarney): throw a context free exception.
   if (resource->length() > static_cast<size_t>(i::String::kMaxLength)) {
     return MaybeLocal<String>();
   }
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   ENTER_V8_NO_SCRIPT_NO_EXCEPTION(i_isolate);
   LOG_API(i_isolate, String, NewExternalTwoByte);
-  i::Handle<i::String> string = i_isolate->factory()
-                                    ->NewExternalStringFromTwoByte(resource)
-                                    .ToHandleChecked();
-  i_isolate->heap()->RegisterExternalString(*string);
-  return Utils::ToLocal(string);
+  if (resource->length() > 0) {
+    i::Handle<i::String> string = i_isolate->factory()
+                                      ->NewExternalStringFromTwoByte(resource)
+                                      .ToHandleChecked();
+    i_isolate->heap()->RegisterExternalString(*string);
+    return Utils::ToLocal(string);
+  } else {
+    return Utils::ToLocal(i_isolate->factory()->empty_string());
+  }
 }
 
 
 Local<String> v8::String::NewExternal(
     Isolate* isolate, v8::String::ExternalStringResource* resource) {
   RETURN_TO_LOCAL_UNCHECKED(NewExternalTwoByte(isolate, resource), String);
 }
 
 
 MaybeLocal<String> v8::String::NewExternalOneByte(
     Isolate* isolate, v8::String::ExternalOneByteStringResource* resource) {
   CHECK(resource && resource->data());
   // TODO(dcarney): throw a context free exception.
   if (resource->length() > static_cast<size_t>(i::String::kMaxLength)) {
     return MaybeLocal<String>();
   }
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   ENTER_V8_NO_SCRIPT_NO_EXCEPTION(i_isolate);
   LOG_API(i_isolate, String, NewExternalOneByte);
-  i::Handle<i::String> string = i_isolate->factory()
-                                    ->NewExternalStringFromOneByte(resource)
-                                    .ToHandleChecked();
-  i_isolate->heap()->RegisterExternalString(*string);
-  return Utils::ToLocal(string);
+  if (resource->length() > 0) {
+    i::Handle<i::String> string = i_isolate->factory()
+                                      ->NewExternalStringFromOneByte(resource)
+                                      .ToHandleChecked();
+    i_isolate->heap()->RegisterExternalString(*string);
+    return Utils::ToLocal(string);
+  } else {
+    return Utils::ToLocal(i_isolate->factory()->empty_string());
+  }
 }
 
 
 Local<String> v8::String::NewExternal(
     Isolate* isolate, v8::String::ExternalOneByteStringResource* resource) {
   RETURN_TO_LOCAL_UNCHECKED(NewExternalOneByte(isolate, resource), String);
 }
 
 
 bool v8::String::MakeExternal(v8::String::ExternalStringResource* resource) {
@@ skipping 3371 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8