Use deferred loading for message catalogs.

pkg/intl/test/message_extraction/message_extraction_test.dart

 // Copyright (c) 2013, 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.
 
 library message_extraction_test;
 
 import 'package:unittest/unittest.dart';
 import 'dart:io';
 import 'dart:async';
 import 'dart:convert';
 import 'package:path/path.dart' as path;
 import '../data_directory.dart';
 
 final dart = Platform.executable;
 
 /** The VM arguments we were given, most important package-root. */
 final vmArgs = Platform.executableArguments;
 
-var tempDir = Directory.systemTemp.createTempSync('message_extraction_test'
-    ).path;
+/**
+ * For testing we move the files into a temporary directory so as not to leave
+ * generated files around after a failed test. For debugging, we omit that
+ * step if [useLocalDirectory] is true. The place we move them to is saved as
+ * [tempDir].
+ */
+String get tempDir => _tempDir == null ? _tempDir = _createTempDir() : _tempDir;
+var _tempDir;
+_createTempDir() => useLocalDirectory ? '.' :
+  Directory.systemTemp.createTempSync('message_extraction_test').path;
+
+var useLocalDirectory = false;
 
 /**
  * Translate a relative file path into this test directory. This is
  * applied to all the arguments of [run]. It will ignore a string that
  * is an absolute path or begins with "--", because some of the arguments
  * might be command-line options.
  */
 String asTestDirPath([String s]) {
   if (s == null || s.startsWith("--") || path.isAbsolute(s)) return s;
   return path.join(intlDirectory, 'test', 'message_extraction', s);
 }
 
 /**
  * Translate a relative file path into our temp directory. This is
  * applied to all the arguments of [run]. It will ignore a string that
  * is an absolute path or begins with "--", because some of the arguments
  * might be command-line options.
  */
 String asTempDirPath([String s]) {
   if (s == null || s.startsWith("--") || path.isAbsolute(s)) return s;
   return path.join(tempDir, s);
 }
 
-main() {
+main(arguments) {
+  // If debugging, use --local to avoid copying everything to temporary
+  // directories to make it even harder to debug. Note that this will also
+  // not delete the generated files, so may require manual cleanup.
+  if (arguments.contains("--local")) {
+    print("Testing using local directory for generated files");
+    useLocalDirectory = true;
+  }
   setUp(copyFilesToTempDirectory);
   test("Test round trip message extraction, translation, code generation, "
       "and printing", () {
     var makeSureWeVerify = expectAsync(runAndVerify);
     return extractMessages(null).then((result) {
       return generateTranslationFiles(result);
     }).then((result) {
       return generateCodeFromTranslation(result);
     }).then(makeSureWeVerify).then(checkResult);
   });
   tearDown(deleteGeneratedFiles);
 }
 
 void copyFilesToTempDirectory() {
+  if (useLocalDirectory) return;
   var files = [asTestDirPath('sample_with_messages.dart'),
       asTestDirPath('part_of_sample_with_messages.dart'),
       asTestDirPath('verify_messages.dart'),
       asTestDirPath('run_and_verify.dart'),
       asTestDirPath('print_to_list.dart')];
   for (var filename in files) {
     var file = new File(filename);
     file.copySync(path.join(tempDir, path.basename(filename)));
   }
 }
 
 void deleteGeneratedFiles() {
+  if (useLocalDirectory) return;
   try {
     var dir = new Directory(tempDir);
     dir.listSync().forEach((x) => x.deleteSync());
     dir.deleteSync();
   } on Error catch (e) {
     print("Failed to delete $tempDir");
     print("Exception:\n$e");
   }
 }
 
@@ skipping 44 matching lines @@
         'intl_messages.json']);
 
 Future<ProcessResult> generateCodeFromTranslation(ProcessResult previousResult)
     => run(previousResult, [asTestDirPath('generate_from_json.dart'),
     '--generated-file-prefix=foo_', 'sample_with_messages.dart',
     'part_of_sample_with_messages.dart', 'translation_fr.json',
     'translation_de_DE.json']);
 
 Future<ProcessResult> runAndVerify(ProcessResult previousResult) => run(
     previousResult, [asTempDirPath('run_and_verify.dart')]);