Async initialization for DateFormat

pkg/intl/date_symbol_data_file.dart

Index: pkg/intl/date_symbol_data_file.dart
===================================================================
--- pkg/intl/date_symbol_data_file.dart	(revision 0)
+++ pkg/intl/date_symbol_data_file.dart	(revision 0)
@@ -0,0 +1,43 @@
+// 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.
+
+/**
+ * This file should be imported, along with date_format.dart in order to read
+ * locale data from files in the file system.
+ */
+
+#library('date_symbol_data_json');
+
+#import("date_symbols.dart");
+#import("lib/lazy_locale_data.dart");
+#import('lib/date_format_internal.dart');
+#import('lib/file_data_reader.dart');
+
+#source("data/dates/localeList.dart");
+
+/**
+ * This should be called for at least one [locale] before any date formatting
+ * methods are called. It sets up the lookup for date symbols using [path].
+ * The [path] parameter should end with a /.
+ * For some implementations this may be a no-op.

[Emily Fortuna, 2012/09/04 20:14:42]

Explain briefly when/why would this be a no-op.

[Alan Knight, 2012/09/04 23:39:03]

Actually, it's not true, because even for the local implementation if you don't
call the initialization function it will fail. Removed.

+ */
+Future initializeDateFormatting(String locale, String path) {
+  var reader = new FileDataReader('${path}symbols/');

[Emily Fortuna, 2012/09/04 20:14:42]

You can use the Path separator from the Platform class:
http://api.dartlang.org/docs/continuous/dart_io/Platform.html#pathSeparator to
have OS-independent code here.

[Alan Knight, 2012/09/04 23:39:03]

Done.

+  initializeDateSymbols(() => new LazyLocaleData(
+      reader, _createDateSymbol, availableLocalesForDateFormatting));
+  var reader2 = new FileDataReader('${path}patterns/');
+  initializeDatePatterns(() => new LazyLocaleData(
+      reader2, (x) => x, availableLocalesForDateFormatting));
+  return initializeIndividualLocaleDateFormatting(
+      (symbols, patterns) {
+        return Futures.wait([
+            symbols.initLocale(locale),
+            patterns.initLocale(locale)]);
+      });
+}
+
+/** Defines how new date symbol entries are created. */
+DateSymbols _createDateSymbol(Map map) {
+  return new DateSymbols.deserializeFromMap(map);
+}