src: fix fatal errors when a current isolate not exist

napi_fatal_error and node watchdog trigger fatal error but rather
running on a thread that hold no current isolate.

PR-URL: nodejs#38624
Reviewed-By: Michael Dawson <midawson@redhat.com>

src/node_errors.cc

@@ -424,6 +424,12 @@ void OnFatalError(const char* location, const char* message) {
   }
 
   Isolate* isolate = Isolate::GetCurrent();
+  // TODO(legendecas): investigate failures on triggering node-report with
+  // nullptr isolates.
+  if (isolate == nullptr) {
+    fflush(stderr);
+    ABORT();
+  }
   Environment* env = Environment::GetCurrent(isolate);
   bool report_on_fatalerror;
   {

test/node-api/test_fatal/test.js

@@ -16,3 +16,4 @@ const p = child_process.spawnSync(
 assert.ifError(p.error);
 assert.ok(p.stderr.toString().includes(
   'FATAL ERROR: test_fatal::Test fatal message'));
+assert.ok(p.status === 134 || p.signal === 'SIGABRT');

test/node-api/test_fatal/test2.js

@@ -16,3 +16,4 @@ const p = child_process.spawnSync(
 assert.ifError(p.error);
 assert.ok(p.stderr.toString().includes(
   'FATAL ERROR: test_fatal::Test fatal message'));
+assert.ok(p.status === 134 || p.signal === 'SIGABRT');

test/node-api/test_fatal/test_fatal.c

@@ -1,12 +1,32 @@
+// For the purpose of this test we use libuv's threading library. When deciding
+// on a threading library for a new project it bears remembering that in the
+// future libuv may introduce API changes which may render it non-ABI-stable,
+// which, in turn, may affect the ABI stability of the project despite its use
+// of N-API.
+#include <uv.h>
 #include <node_api.h>
 #include "../../js-native-api/common.h"
 
+static uv_thread_t uv_thread;
+
+static void work_thread(void* data) {
+  napi_fatal_error("work_thread", NAPI_AUTO_LENGTH,
+      "foobar", NAPI_AUTO_LENGTH);
+}
+
 static napi_value Test(napi_env env, napi_callback_info info) {
   napi_fatal_error("test_fatal::Test", NAPI_AUTO_LENGTH,
                    "fatal message", NAPI_AUTO_LENGTH);
   return NULL;
 }
 
+static napi_value TestThread(napi_env env, napi_callback_info info) {
+  NAPI_ASSERT(env,
+      (uv_thread_create(&uv_thread, work_thread, NULL) == 0),
+      "Thread creation");
+  return NULL;
+}
+
 static napi_value TestStringLength(napi_env env, napi_callback_info info) {
   napi_fatal_error("test_fatal::TestStringLength", 16, "fatal message", 13);
   return NULL;
@@ -16,6 +36,7 @@ static napi_value Init(napi_env env, napi_value exports) {
   napi_property_descriptor properties[] = {
     DECLARE_NAPI_PROPERTY("Test", Test),
     DECLARE_NAPI_PROPERTY("TestStringLength", TestStringLength),
+    DECLARE_NAPI_PROPERTY("TestThread", TestThread),
   };
 
   NAPI_CALL(env, napi_define_properties(

test/node-api/test_fatal/test_threads.js

@@ -0,0 +1,20 @@
+'use strict';
+const common = require('../../common');
+const assert = require('assert');
+const child_process = require('child_process');
+const test_fatal = require(`./build/${common.buildType}/test_fatal`);
+
+// Test in a child process because the test code will trigger a fatal error
+// that crashes the process.
+if (process.argv[2] === 'child') {
+  test_fatal.TestThread();
+  // Busy loop to allow the work thread to abort.
+  while (true) {}
+}
+
+const p = child_process.spawnSync(
+  process.execPath, [ __filename, 'child' ]);
+assert.ifError(p.error);
+assert.ok(p.stderr.toString().includes(
+  'FATAL ERROR: work_thread foobar'));
+assert.ok(p.status === 134 || p.signal === 'SIGABRT');