Adds facilities for extracting Intl.message calls and generating code from translations

pkg/intl/lib/message_lookup_local.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.
-
-/**
- * Message/plural format library with locale support. This can have different
- * implementations based on the mechanism for finding the localized versions
- * of messages. This version expects them to be in a library named e.g.
- * 'messages_en_US'. The prefix is set in the [initializeMessages] call, which
- * must be made for a locale before any lookups can be done.
- *
- * See Intl class comment or `tests/message_format_test.dart` for more examples.
- */
- //TODO(efortuna): documentation example involving the offset parameter?
-
-library message_lookup_local;
-
-import 'dart:async';
-import 'intl.dart';
-import 'src/intl_helpers.dart';
-import 'dart:mirrors';
-
-/**
- * Initialize the user messages for [localeName]. Note that this is an ASYNC
- * operation. This must be called before attempting to use messages in
- * [localeName].
- */
-Future initializeMessages(localeName, [String source = 'messages_']) {
-  initializeInternalMessageLookup(
-      () => new MessageLookupLocal(localeName, source));
-  _initializeMessagesForLocale(localeName);
-  return new Future.immediate(null);
-}
-
-void _initializeMessagesForLocale(String localeName) {}
-
-class MessageLookupLocal {
-  /** Prevent infinite recursion when looking up the message. */
-  bool _lookupInProgress = false;
-
-  /** The libraries we can look in for internationalization messages. */
-  Map<String, LibraryMirror> _libraries;
-
-  /** The prefix used to find libraries that contain localized messages.
-   * So, if this is 'messages_' we would look for messages for the locale
-   * 'pt_BR' in a library named 'messages_pt_BR'.
-   */
-  String _sourcePrefix;
-
-  /**
-   * Constructor. The [localeName] is of the form 'en' or 'en_US'.
-   *The [source] parameter defines the prefix that is used to find
-   * libraries that contain localized messages. So with the default value of
-   * 'messages_', we would look for messages for the locale 'pt_BR' in a library
-   * named 'messages_pt_BR'.
-   */
-  MessageLookupLocal(String localeName, this._sourcePrefix) {
-    _libraries = currentMirrorSystem().libraries;
-  }
-
-  /**
-   * Return true if the locale exists, or if it is null. The null case
-   * is interpreted to mean that we use the default locale.
-   */
-  bool localeExists(localeName) {
-    if (localeName == null) return false;
-    return _libraries['$_sourcePrefix$localeName'] != null;
-  }
-
-  /**
-   * Return the localized version of a message. We are passed the original
-   * version of the message, which consists of a
-   * [message_str] that will be translated, and which may be interpolated
-   * based on one or more variables, a [desc] providing a description of usage
-   * for the [message_str], and a map of [examples] for each data element to be
-   * substituted into the message.
-   *
-   * For example, if message="Hello, $name", then
-   * examples = {'name': 'Sparky'}. If not using the user's default locale, or
-   * if the locale is not easily detectable, explicitly pass [locale].
-   *
-   * The values of [desc] and [examples] are not used at run-time but are only
-   * made available to the translators, so they MUST be simple Strings available
-   * at compile time: no String interpolation or concatenation.
-   * The expected usage of this is inside a function that takes as parameters
-   * the variables used in the interpolated string.
-   *
-   * Ultimately, the information about the enclosing function and its arguments
-   * will be extracted automatically but for the time being it must be passed
-   * explicitly in the [name] and [args] arguments.
-   */
-  Future<String> lookupMessage(String message_str, [final String desc='',
-      final Map examples=const {}, String locale,
-      String name, List<String> args]) {
-    if (name == null) return new Future.immediate(message_str);
-    // The translations also make use of Intl.message, so we need to not
-    // recurse and just stop when we find the first substitution.
-    if (_lookupInProgress) return new Future.immediate(message_str);
-    _lookupInProgress = true;
-    var result;
-    try {
-      var actualLocale = (locale == null) ? Intl.getCurrentLocale() : locale;
-      // For this usage, if the locale doesn't exist for messages, just return
-      // it and we'll fall back to the original version.
-      var verifiedLocale =
-          Intl.verifiedLocale(
-              actualLocale,
-              localeExists,
-              onFailure: (locale)=>locale);
-      LibraryMirror messagesForThisLocale =
-          _libraries['$_sourcePrefix$verifiedLocale'];
-      if (messagesForThisLocale == null) {
-        return new Future.immediate(message_str);
-      }
-      MethodMirror localized = messagesForThisLocale.functions[name];
-      if (localized == null) return new Future.immediate(message_str);
-      result = messagesForThisLocale.invoke(localized.simpleName, args);
-    } finally {
-      _lookupInProgress = false;
-    }
-    return result.then((value) => value.reflectee);
-  }
-}