n-api: add code parameter to error helpers

In support of the effort to add error codes to all errors generated by Node.js, add an optional code parameter to the helper functions used to throw/create errors in N-API. Backport-PR-URL: #19447 PR-URL: #13988 Fixes: #13933 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Anna Henningsen <anna@addaleax.net>
nodejs · Apr 16, 2018 · 57be12e · 57be12e
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diff --git a/doc/api/n-api.md b/doc/api/n-api.md
@@ -323,6 +323,31 @@ code needs to create an Error object: [`napi_create_error`][],
 where result is the napi_value that refers to the newly created
 JavaScript Error object.
 
+The Node.js project is adding error codes to all of the errors
+generated internally.  The goal is for applications to use these
+error codes for all error checking. The associated error messages
+will remain, but will only be meant to be used for logging and
+display with the expectation that the message can change without
+SemVer applying. In order to support this model with N-API, both
+in internal functionality and for module specific functionality
+(as its good practice), the `throw_` and `create_` functions
+take an optional code parameter which is the string for the code
+to be added to the error object.  If the optional parameter is NULL
+then no code will be associated with the error. If a code is provided,
+the name associated with the error is also updated to be:
+
+```
+originalName [code]
+```
+
+where originalName is the original name associated with the error
+and code is the code that was provided.  For example if the code
+is 'ERR_ERROR_1' and a TypeError is being created the name will be:
+
+```
+TypeError [ERR_ERROR_1]
+```
+
 #### napi_throw
 <!-- YAML
 added: v8.0.0
@@ -343,9 +368,12 @@ This API throws the JavaScript Error provided.
 added: v8.0.0
 -->
 ```C
-NODE_EXTERN napi_status napi_throw_error(napi_env env, const char* msg);
+NODE_EXTERN napi_status napi_throw_error(napi_env env,
+                                         const char* code,
+                                         const char* msg);
 ```
 - `[in] env`: The environment that the API is invoked under.
+- `[in] code`: Optional error code to be set on the error.
 - `[in] msg`: C string representing the text to be associated with
 the error.
 
@@ -358,9 +386,12 @@ This API throws a JavaScript Error with the text provided.
 added: v8.0.0
 -->
 ```C
-NODE_EXTERN napi_status napi_throw_type_error(napi_env env, const char* msg);
+NODE_EXTERN napi_status napi_throw_type_error(napi_env env,
+                                              const char* code,
+                                              const char* msg);
 ```
 - `[in] env`: The environment that the API is invoked under.
+- `[in] code`: Optional error code to be set on the error.
 - `[in] msg`: C string representing the text to be associated with
 the error.
 
@@ -373,9 +404,12 @@ This API throws a JavaScript TypeError with the text provided.
 added: v8.0.0
 -->
 ```C
-NODE_EXTERN napi_status napi_throw_range_error(napi_env env, const char* msg);
+NODE_EXTERN napi_status napi_throw_range_error(napi_env env,
+                                               const char* code,
+                                               const char* msg);
 ```
 - `[in] env`: The environment that the API is invoked under.
+- `[in] code`: Optional error code to be set on the error.
 - `[in] msg`: C string representing the text to be associated with
 the error.
 
@@ -409,10 +443,13 @@ added: v8.0.0
 -->
 ```C
 NODE_EXTERN napi_status napi_create_error(napi_env env,
+                                          napi_value code,
                                           napi_value msg,
                                           napi_value* result);
 ```
 - `[in] env`: The environment that the API is invoked under.
+- `[in] code`: Optional `napi_value` with the string for the error code to
+               be associated with the error.
 - `[in] msg`: napi_value that references a JavaScript String to be
 used as the message for the Error.
 - `[out] result`: `napi_value` representing the error created.
@@ -427,10 +464,13 @@ added: v8.0.0
 -->
 ```C
 NODE_EXTERN napi_status napi_create_type_error(napi_env env,
+                                               napi_value code,
                                                napi_value msg,
                                                napi_value* result);
 ```
 - `[in] env`: The environment that the API is invoked under.
+- `[in] code`: Optional `napi_value` with the string for the error code to
+               be associated with the error.
 - `[in] msg`: napi_value that references a JavaScript String to be
 used as the message for the Error.
 - `[out] result`: `napi_value` representing the error created.
@@ -446,10 +486,13 @@ added: v8.0.0
 -->
 ```C
 NODE_EXTERN napi_status napi_create_range_error(napi_env env,
+                                                napi_value code,
                                                 const char* msg,
                                                 napi_value* result);
 ```
 - `[in] env`: The environment that the API is invoked under.
+- `[in] code`: Optional `napi_value` with the string for the error code to
+               be associated with the error.
 - `[in] msg`: napi_value that references a JavaScript String to be
 used as the message for the Error.
 - `[out] result`: `napi_value` representing the error created.

diff --git a/src/node_api.cc b/src/node_api.cc
@@ -21,6 +21,7 @@
 #include "node_internals.h"
 #include "env-inl.h"
 #include "node_api_backport.h"
+#include "util.h"
 
 #define NAPI_VERSION  1
 
@@ -1525,7 +1526,61 @@ napi_status napi_create_symbol(napi_env env,
   return GET_RETURN_STATUS(env);
 }
 
+static napi_status set_error_code(napi_env env,
+                                  v8::Local<v8::Value> error,
+                                  napi_value code,
+                                  const char* code_cstring) {
+  if ((code != nullptr) || (code_cstring != nullptr)) {
+    v8::Isolate* isolate = env->isolate;
+    v8::Local<v8::Context> context = isolate->GetCurrentContext();
+    v8::Local<v8::Object> err_object = error.As<v8::Object>();
+
+    v8::Local<v8::Value> code_value = v8impl::V8LocalValueFromJsValue(code);
+    if (code != nullptr) {
+      code_value = v8impl::V8LocalValueFromJsValue(code);
+      RETURN_STATUS_IF_FALSE(env, code_value->IsString(), napi_string_expected);
+    } else {
+      CHECK_NEW_FROM_UTF8(env, code_value, code_cstring);
+    }
+
+    v8::Local<v8::Name> code_key;
+    CHECK_NEW_FROM_UTF8(env, code_key, "code");
+
+    v8::Maybe<bool> set_maybe = err_object->Set(context, code_key, code_value);
+    RETURN_STATUS_IF_FALSE(env,
+                           set_maybe.FromMaybe(false),
+                           napi_generic_failure);
+
+    // now update the name to be "name [code]" where name is the
+    // original name and code is the code associated with the Error
+    v8::Local<v8::String> name_string;
+    CHECK_NEW_FROM_UTF8(env, name_string, "");
+    v8::Local<v8::Name> name_key;
+    CHECK_NEW_FROM_UTF8(env, name_key, "name");
+
+    auto maybe_name = err_object->Get(context, name_key);
+    if (!maybe_name.IsEmpty()) {
+      v8::Local<v8::Value> name = maybe_name.ToLocalChecked();
+      if (name->IsString()) {
+        name_string = v8::String::Concat(name_string, name.As<v8::String>());
+      }
+    }
+    name_string = v8::String::Concat(name_string,
+                                     FIXED_ONE_BYTE_STRING(isolate, " ["));
+    name_string = v8::String::Concat(name_string, code_value.As<v8::String>());
+    name_string = v8::String::Concat(name_string,
+                                     FIXED_ONE_BYTE_STRING(isolate, "]"));
+
+    set_maybe = err_object->Set(context, name_key, name_string);
+    RETURN_STATUS_IF_FALSE(env,
+                           set_maybe.FromMaybe(false),
+                           napi_generic_failure);
+  }
+  return napi_ok;
+}
+
 napi_status napi_create_error(napi_env env,
+                              napi_value code,
                               napi_value msg,
                               napi_value* result) {
   NAPI_PREAMBLE(env);
@@ -1535,13 +1590,18 @@ napi_status napi_create_error(napi_env env,
   v8::Local<v8::Value> message_value = v8impl::V8LocalValueFromJsValue(msg);
   RETURN_STATUS_IF_FALSE(env, message_value->IsString(), napi_string_expected);
 
-  *result = v8impl::JsValueFromV8LocalValue(v8::Exception::Error(
-      message_value.As<v8::String>()));
+  v8::Local<v8::Value> error_obj =
+      v8::Exception::Error(message_value.As<v8::String>());
+  napi_status status = set_error_code(env, error_obj, code, nullptr);
+  if (status != napi_ok) return status;
+
+  *result = v8impl::JsValueFromV8LocalValue(error_obj);
 
   return GET_RETURN_STATUS(env);
 }
 
 napi_status napi_create_type_error(napi_env env,
+                                   napi_value code,
                                    napi_value msg,
                                    napi_value* result) {
   NAPI_PREAMBLE(env);
@@ -1551,13 +1611,18 @@ napi_status napi_create_type_error(napi_env env,
   v8::Local<v8::Value> message_value = v8impl::V8LocalValueFromJsValue(msg);
   RETURN_STATUS_IF_FALSE(env, message_value->IsString(), napi_string_expected);
 
-  *result = v8impl::JsValueFromV8LocalValue(v8::Exception::TypeError(
-      message_value.As<v8::String>()));
+  v8::Local<v8::Value> error_obj =
+      v8::Exception::TypeError(message_value.As<v8::String>());
+  napi_status status = set_error_code(env, error_obj, code, nullptr);
+  if (status != napi_ok) return status;
+
+  *result = v8impl::JsValueFromV8LocalValue(error_obj);
 
   return GET_RETURN_STATUS(env);
 }
 
 napi_status napi_create_range_error(napi_env env,
+                                    napi_value code,
                                     napi_value msg,
                                     napi_value* result) {
   NAPI_PREAMBLE(env);
@@ -1567,8 +1632,12 @@ napi_status napi_create_range_error(napi_env env,
   v8::Local<v8::Value> message_value = v8impl::V8LocalValueFromJsValue(msg);
   RETURN_STATUS_IF_FALSE(env, message_value->IsString(), napi_string_expected);
 
-  *result = v8impl::JsValueFromV8LocalValue(v8::Exception::RangeError(
-      message_value.As<v8::String>()));
+  v8::Local<v8::Value> error_obj =
+      v8::Exception::RangeError(message_value.As<v8::String>());
+  napi_status status = set_error_code(env, error_obj, code, nullptr);
+  if (status != napi_ok) return status;
+
+  *result = v8impl::JsValueFromV8LocalValue(error_obj);
 
   return GET_RETURN_STATUS(env);
 }
@@ -1741,40 +1810,58 @@ napi_status napi_throw(napi_env env, napi_value error) {
   return napi_clear_last_error(env);
 }
 
-napi_status napi_throw_error(napi_env env, const char* msg) {
+napi_status napi_throw_error(napi_env env,
+                             const char* code,
+                             const char* msg) {
   NAPI_PREAMBLE(env);
 
   v8::Isolate* isolate = env->isolate;
   v8::Local<v8::String> str;
   CHECK_NEW_FROM_UTF8(env, str, msg);
 
-  isolate->ThrowException(v8::Exception::Error(str));
+  v8::Local<v8::Value> error_obj = v8::Exception::Error(str);
+  napi_status status = set_error_code(env, error_obj, nullptr, code);
+  if (status != napi_ok) return status;
+
+  isolate->ThrowException(error_obj);
   // any VM calls after this point and before returning
   // to the javascript invoker will fail
   return napi_clear_last_error(env);
 }
 
-napi_status napi_throw_type_error(napi_env env, const char* msg) {
+napi_status napi_throw_type_error(napi_env env,
+                                  const char* code,
+                                  const char* msg) {
   NAPI_PREAMBLE(env);
 
   v8::Isolate* isolate = env->isolate;
   v8::Local<v8::String> str;
   CHECK_NEW_FROM_UTF8(env, str, msg);
 
-  isolate->ThrowException(v8::Exception::TypeError(str));
+  v8::Local<v8::Value> error_obj = v8::Exception::TypeError(str);
+  napi_status status = set_error_code(env, error_obj, nullptr, code);
+  if (status != napi_ok) return status;
+
+  isolate->ThrowException(error_obj);
   // any VM calls after this point and before returning
   // to the javascript invoker will fail
   return napi_clear_last_error(env);
 }
 
-napi_status napi_throw_range_error(napi_env env, const char* msg) {
+napi_status napi_throw_range_error(napi_env env,
+                                   const char* code,
+                                   const char* msg) {
   NAPI_PREAMBLE(env);
 
   v8::Isolate* isolate = env->isolate;
   v8::Local<v8::String> str;
   CHECK_NEW_FROM_UTF8(env, str, msg);
 
-  isolate->ThrowException(v8::Exception::RangeError(str));
+  v8::Local<v8::Value> error_obj = v8::Exception::RangeError(str);
+  napi_status status = set_error_code(env, error_obj, nullptr, code);
+  if (status != napi_ok) return status;
+
+  isolate->ThrowException(error_obj);
   // any VM calls after this point and before returning
   // to the javascript invoker will fail
   return napi_clear_last_error(env);
@@ -2394,7 +2481,9 @@ napi_status napi_instanceof(napi_env env,
   CHECK_TO_OBJECT(env, context, ctor, constructor);
 
   if (!ctor->IsFunction()) {
-    napi_throw_type_error(env, "constructor must be a function");
+    napi_throw_type_error(env,
+                          "ERR_NAPI_CONS_FUNCTION",
+                          "Constructor must be a function");
 
     return napi_set_last_error(env, napi_function_expected);
   }
@@ -2462,7 +2551,10 @@ napi_status napi_instanceof(napi_env env,
 
   v8::Local<v8::Value> prototype_property = maybe_prototype.ToLocalChecked();
   if (!prototype_property->IsObject()) {
-    napi_throw_type_error(env, "constructor.prototype must be an object");
+    napi_throw_type_error(
+        env,
+        "ERR_NAPI_CONS_PROTOTYPE_OBJECT",
+        "Constructor.prototype must be an object");
 
     return napi_set_last_error(env, napi_object_expected);
   }

diff --git a/src/node_api.h b/src/node_api.h
@@ -142,12 +142,15 @@ NAPI_EXTERN napi_status napi_create_function(napi_env env,
                                              void* data,
                                              napi_value* result);
 NAPI_EXTERN napi_status napi_create_error(napi_env env,
+                                          napi_value code,
                                           napi_value msg,
                                           napi_value* result);
 NAPI_EXTERN napi_status napi_create_type_error(napi_env env,
+                                               napi_value code,
                                                napi_value msg,
                                                napi_value* result);
 NAPI_EXTERN napi_status napi_create_range_error(napi_env env,
+                                                napi_value code,
                                                 napi_value msg,
                                                 napi_value* result);
 
@@ -404,9 +407,15 @@ NAPI_EXTERN napi_status napi_escape_handle(napi_env env,
 
 // Methods to support error handling
 NAPI_EXTERN napi_status napi_throw(napi_env env, napi_value error);
-NAPI_EXTERN napi_status napi_throw_error(napi_env env, const char* msg);
-NAPI_EXTERN napi_status napi_throw_type_error(napi_env env, const char* msg);
-NAPI_EXTERN napi_status napi_throw_range_error(napi_env env, const char* msg);
+NAPI_EXTERN napi_status napi_throw_error(napi_env env,
+                                         const char* code,
+                                         const char* msg);
+NAPI_EXTERN napi_status napi_throw_type_error(napi_env env,
+                                         const char* code,
+                                         const char* msg);
+NAPI_EXTERN napi_status napi_throw_range_error(napi_env env,
+                                         const char* code,
+                                         const char* msg);
 NAPI_EXTERN napi_status napi_is_error(napi_env env,
                                       napi_value value,
                                       bool* result);

diff --git a/test/addons-napi/common.h b/test/addons-napi/common.h
@@ -12,7 +12,7 @@
       const char* error_message = error_info->error_message != NULL ?    \
         error_info->error_message :                                      \
         "empty error message";                                           \
-      napi_throw_error((env), error_message);                            \
+      napi_throw_error((env), NULL, error_message);                      \
     }                                                                    \
   } while (0)
 
@@ -21,6 +21,7 @@
     if (!(assertion)) {                                                  \
       napi_throw_error(                                                  \
           (env),                                                         \
+        NULL,                                                            \
           "assertion (" #assertion ") failed: " message);                \
       return ret_val;                                                    \
     }                                                                    \