Fix native extension lookup

tests/standalone/io/test_extension_fail_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Dart test program for testing native extensions.
 
 import "package:path/path.dart";
 import "dart:async";
 import "dart:io";
 
@@ skipping 17 matching lines @@
     case 'macos':
       return join(buildDirectory, 'libtest_extension.dylib');
     case 'windows':
       return join(buildDirectory, 'test_extension.dll');
     default:
       throw new StateError(
           'Unknown operating system ${Platform.operatingSystem}');
   }
 }
 
-void main() {
+bool checkExitCode(int code) {
+  return ((code == 255) || (code == 253));
+}
+
+bool checkStdError(String err) {
+  return err.contains("Unhandled exception:") ||
+         err.contains("Relative paths for dart extensions are not supported");
+}
+
+// name is either "extension" or "relative_extension"
+Future test(String name, bool checkForBall) {
   String scriptDirectory = dirname(Platform.script.toFilePath());
   String buildDirectory = dirname(Platform.executable);
   Directory tempDirectory =
-      Directory.systemTemp.createTempSync('dart_test_extension_fail');
+      Directory.systemTemp.createTempSync('dart_test_${name}_fail');
   String testDirectory = tempDirectory.path;
 
   // Copy test_extension shared library, test_extension.dart and
   // test_extension_fail_tester.dart to the temporary test directory.
   copyFileToDirectory(getExtensionPath(buildDirectory),
                       testDirectory).then((_) {
-    var extensionDartFile = join(scriptDirectory, 'test_extension.dart');
+    var extensionDartFile = join(scriptDirectory, 'test_${name}.dart');
     return copyFileToDirectory(extensionDartFile, testDirectory);
   }).then((_) {
     var testExtensionTesterFile =
-        join(scriptDirectory, 'test_extension_fail_tester.dart');
+        join(scriptDirectory, 'test_${name}_fail_tester.dart');
     return copyFileToDirectory(testExtensionTesterFile, testDirectory);
   }).then((_) {
-    var script = join(testDirectory, 'test_extension_fail_tester.dart');
-    return Process.run(Platform.executable, [script]);
+    var script = join(testDirectory, 'test_${name}_fail_tester.dart');
+    return Process.run(Platform.executable, ['--trace-loading', script]);
   }).then((ProcessResult result) {
     print("ERR: ${result.stderr}\n\n");
     print("OUT: ${result.stdout}\n\n");
-    if (result.exitCode != 255) {
-      throw new StateError("bad exit code");
+    if (!checkExitCode(result.exitCode)) {
+      throw new StateError("bad exit code: ${result.exitCode}");
     }
-    if (!result.stderr.contains("Unhandled exception:")) {
+    if (!checkStdError(result.stderr)) {
       throw new StateError("stderr doesn't contain unhandled exception.");
     }
-    if (!result.stderr.contains("ball")) {
-      throw new StateError("stderr doesn't contain 'ball'.");
+    if (checkForBall) {
+      if (!result.stderr.contains("ball")) {
+        throw new StateError("stderr doesn't contain 'ball'.");
+      }
     }
   }).whenComplete(() => tempDirectory.deleteSync(recursive: true));
 }
+
+main() async {
+  await test("extension", true);
+  await test("relative_extension", false);
+}