src: attach error to stack on displayErrors

The vm module's displayErrors option attaches error arrow
messages as a hidden property. Later, core JavaScript code
can optionally decorate the error stack with the arrow message.
However, when user code catches an error, it has no way to
access the arrow message. This commit changes the behavior of
displayErrors to mean "decorate the error stack if an error
occurs."

Fixes: https://github.com/nodejs/node/issues/4835
PR-URL: https://github.com/nodejs/node/pull/4874
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

1 files changed, 26 insertions, 2 deletions

diff --git a/src/node_contextify.cc b/src/node_contextify.cc
index 31d98853d3..7ca622de43 100644
--- a/src/node_contextify.cc
+++ b/src/node_contextify.cc
@@ -541,7 +541,7 @@ class ContextifyScript : public BaseObject {
 
     if (v8_script.IsEmpty()) {
       if (display_errors) {
-        AppendExceptionLine(env, try_catch.Exception(), try_catch.Message());
+        DecorateErrorStack(env, try_catch);
       }
       try_catch.ReThrow();
       return;
@@ -640,6 +640,30 @@ class ContextifyScript : public BaseObject {
     }
   }
 
+  static void DecorateErrorStack(Environment* env, const TryCatch& try_catch) {
+    Local<Value> exception = try_catch.Exception();
+
+    if (!exception->IsObject())
+      return;
+
+    Local<Object> err_obj = exception.As<Object>();
+
+    if (IsExceptionDecorated(env, err_obj))
+      return;
+
+    AppendExceptionLine(env, exception, try_catch.Message());
+    Local<Value> stack = err_obj->Get(env->stack_string());
+    Local<Value> arrow = err_obj->GetHiddenValue(env->arrow_message_string());
+
+    if (!(stack->IsString() && arrow->IsString()))
+      return;
+
+    Local<String> decorated_stack = String::Concat(arrow.As<String>(),
+                                                   stack.As<String>());
+    err_obj->Set(env->stack_string(), decorated_stack);
+    err_obj->SetHiddenValue(env->decorated_string(), True(env->isolate()));
+  }
+
   static int64_t GetTimeoutArg(const FunctionCallbackInfo<Value>& args,
                                const int i) {
     if (args[i]->IsUndefined() || args[i]->IsString()) {
@@ -816,7 +840,7 @@ class ContextifyScript : public BaseObject {
     if (result.IsEmpty()) {
       // Error occurred during execution of the script.
       if (display_errors) {
-        AppendExceptionLine(env, try_catch.Exception(), try_catch.Message());
+        DecorateErrorStack(env, try_catch);
       }
       try_catch.ReThrow();
       return false;