n-api: add napi_fatal_exception

Add function to trigger and uncaught exception.
Useful if an async callback throws an exception with
no way to recover.

Backport-PR-URL: https://github.com/nodejs/node/pull/19447
PR-URL: https://github.com/nodejs/node/pull/19337
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

doc/api/n-api.md

@@ -539,6 +539,20 @@ This API returns true if an exception is pending.
 
 This API can be called even if there is a pending JavaScript exception.
 
+#### napi_fatal_exception
+<!-- YAML
+added: REPLACEME
+-->
+```C
+napi_status napi_fatal_exception(napi_env env, napi_value err);
+```
+
+- `[in] env`: The environment that the API is invoked under.
+- `[in] err`: The error you want to pass to `uncaughtException`.
+
+Trigger an `uncaughtException` in JavaScript. Useful if an async
+callback throws an exception with no way to recover.
+
 ### Fatal Errors
 
 In the event of an unrecoverable error in a native module, a fatal error can be

src/node_api.cc

@@ -293,6 +293,13 @@ v8::Local<v8::Value> V8LocalValueFromJsValue(napi_value v) {
   return local;
 }
 
+static inline void trigger_fatal_exception(
+    napi_env env, v8::Local<v8::Value> local_err) {
+  v8::Local<v8::Message> local_msg =
+    v8::Exception::CreateMessage(env->isolate, local_err);
+  node::FatalException(env->isolate, local_err, local_msg);
+}
+
 static inline napi_status V8NameFromPropertyDescriptor(napi_env env,
                                          const napi_property_descriptor* p,
                                          v8::Local<v8::Name>* result) {
@@ -967,6 +974,16 @@ napi_status napi_get_last_error_info(napi_env env,
   return napi_ok;
 }
 
+napi_status napi_fatal_exception(napi_env env, napi_value err) {
+  NAPI_PREAMBLE(env);
+  CHECK_ARG(env, err);
+
+  v8::Local<v8::Value> local_err = v8impl::V8LocalValueFromJsValue(err);
+  v8impl::trigger_fatal_exception(env, local_err);
+
+  return napi_clear_last_error(env);
+}
+
 NAPI_NO_RETURN void napi_fatal_error(const char* location,
                                      size_t location_len,
                                      const char* message,
@@ -3457,10 +3474,9 @@ class Work : public node::AsyncResource {
       // report it as a fatal exception. (There is no JavaScript on the
       // callstack that can possibly handle it.)
       if (!env->last_exception.IsEmpty()) {
-        v8::TryCatch try_catch(env->isolate);
-        env->isolate->ThrowException(
-          v8::Local<v8::Value>::New(env->isolate, env->last_exception));
-        node::FatalException(env->isolate, try_catch);
+        v8::Local<v8::Value> local_err = v8::Local<v8::Value>::New(
+          env->isolate, env->last_exception);
+        v8impl::trigger_fatal_exception(env, local_err);
       }
     }
   }

src/node_api.h

@@ -103,6 +103,8 @@ NAPI_EXTERN napi_status
 napi_get_last_error_info(napi_env env,
                          const napi_extended_error_info** result);
 
+NAPI_EXTERN napi_status napi_fatal_exception(napi_env env, napi_value err);
+
 NAPI_EXTERN NAPI_NO_RETURN void napi_fatal_error(const char* location,
                                                  size_t location_len,
                                                  const char* message,

src/node_internals.h

@@ -118,6 +118,11 @@ void GetSockOrPeerName(const v8::FunctionCallbackInfo<v8::Value>& args) {
   args.GetReturnValue().Set(err);
 }
 
+void FatalException(v8::Isolate* isolate,
+                    v8::Local<v8::Value> error,
+                    v8::Local<v8::Message> message);
+
+
 void SignalExit(int signo);
 #ifdef __POSIX__
 void RegisterSignalHandler(int signal,

test/addons-napi/test_async/test-uncaught.js

@@ -0,0 +1,18 @@
+'use strict';
+const common = require('../../common');
+const assert = require('assert');
+const test_async = require(`./build/${common.buildType}/test_async`);
+
+process.on('uncaughtException', common.mustCall(function(err) {
+  try {
+    throw new Error('should not fail');
+  } catch (err) {
+    assert.strictEqual(err.message, 'should not fail');
+  }
+  assert.strictEqual(err.message, 'uncaught');
+}));
+
+// Successful async execution and completion callback.
+test_async.Test(5, {}, common.mustCall(function() {
+  throw new Error('uncaught');
+}));

test/addons-napi/test_fatal_exception/binding.gyp

@@ -0,0 +1,8 @@
+{
+  "targets": [
+    {
+      "target_name": "test_fatal_exception",
+      "sources": [ "test_fatal_exception.c" ]
+    }
+  ]
+}

test/addons-napi/test_fatal_exception/test.js

@@ -0,0 +1,11 @@
+'use strict';
+const common = require('../../common');
+const assert = require('assert');
+const test_fatal = require(`./build/${common.buildType}/test_fatal_exception`);
+
+process.on('uncaughtException', common.mustCall(function(err) {
+  assert.strictEqual(err.message, 'fatal error');
+}));
+
+const err = new Error('fatal error');
+test_fatal.Test(err);

test/addons-napi/test_fatal_exception/test_fatal_exception.c

@@ -0,0 +1,26 @@
+#include <node_api.h>
+#include "../common.h"
+
+napi_value Test(napi_env env, napi_callback_info info) {
+  napi_value err;
+  size_t argc = 1;
+
+  NAPI_CALL(env, napi_get_cb_info(env, info, &argc, &err, NULL, NULL));
+
+  NAPI_CALL(env, napi_fatal_exception(env, err));
+
+  return NULL;
+}
+
+napi_value Init(napi_env env, napi_value exports) {
+  napi_property_descriptor properties[] = {
+    DECLARE_NAPI_PROPERTY("Test", Test),
+  };
+
+  NAPI_CALL(env, napi_define_properties(
+      env, exports, sizeof(properties) / sizeof(*properties), properties));
+
+  return exports;
+}
+
+NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)