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

pkg/intl/lib/message_lookup_by_library.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;
+library message_lookup_by_library;
 
 import 'dart:async';
 import 'intl.dart';
 import 'src/intl_helpers.dart';
-import 'dart:mirrors';
+
+class CompositeMessageLookup {

[Emily Fortuna, 2013/03/13 18:54:43]

some documentation explaining this class, please?

[Alan Knight, 2013/03/14 17:49:05]

Done.

+  Map<String,MessageLookupByLibrary> availableMessages = new Map();
+
+  bool localeExists(localeName) => availableMessages.containsKey(localeName);
+
+  lookupMessage(String message_str, [final String desc='',
+      final Map examples=const {}, String locale,
+      String name, List<String> args]) {
+    var actualLocale = (locale == null) ? Intl.getCurrentLocale() : locale;
+      // For this usage, if the locale doesn't exist for messages, just return

[Emily Fortuna, 2013/03/13 18:54:43]

random indentation?

[Alan Knight, 2013/03/14 17:49:05]

Not random, I put each argument to the function on a separate line, and indented
them four spaces, which seemed to be one of the permitted things in the style
guide. And I put the start of the function call on a separate line because it
seemed clearer to have it indented less than its arguments. But I'm not fussy
about the formatting. How would you prefer it to look?

[Emily Fortuna, 2013/03/14 19:45:00]

No, that's totally fine. I was complaining that lines 41-47 seem to all be
indented two extra spaces for no clear reason.

[Alan Knight, 2013/03/14 20:50:04]

Doh! Done.

+      // it and we'll fall back to the original version.
+      var verifiedLocale =
+          Intl.verifiedLocale(
+              actualLocale,
+              localeExists,
+              onFailure: (locale)=>locale);
+    var messages = availableMessages[verifiedLocale];
+    if (messages == null) return message_str;
+    return messages.
+        lookupMessage(message_str, desc, examples, locale, name, args);
+  }
+
+  addLocale(String localeName, Function findLocale) {
+    if (localeExists(localeName)) return;
+    var newLocale = findLocale(localeName);
+    if (newLocale != null) {
+      availableMessages[localeName] = newLocale;
+    }
+  }
+}
 
 /**
- * Initialize the user messages for [localeName]. Note that this is an ASYNC
- * operation. This must be called before attempting to use messages in
- * [localeName].
+ * This provides an abstract class for messages looked up in generated code.
+ * Each locale will have a separate subclass of this class with its set of
+ * messages. See generate_localized.dart.
  */
-Future initializeMessages(localeName, [String source = 'messages_']) {
-  initializeInternalMessageLookup(
-      () => new MessageLookupLocal(localeName, source));
-  _initializeMessagesForLocale(localeName);
-  return new Future.immediate(null);
-}
-
-void _initializeMessagesForLocale(String localeName) {}
-
-class MessageLookupLocal {
+abstract class MessageLookupByLibrary {
   /** 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'.
+  /**
+   * Return true if the locale exists, or if it is null. Null is treated
+   * as meaning that we use the default locale.
    */
-  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;
-  }
+  bool localeExists(localeName);
 
   /**
    * 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='',
+  lookupMessage(String message_str, [final String desc='',

[Emily Fortuna, 2013/03/13 18:54:43]

list return type? String?

[Alan Knight, 2013/03/14 17:49:05]

Done.

       final Map examples=const {}, String locale,
       String name, List<String> args]) {
-    if (name == null) return new Future.immediate(message_str);
+    if (name == null) return 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);
+    if (_lookupInProgress) return message_str;

[Emily Fortuna, 2013/03/13 18:54:43]

can we combine this branch with line 91, so we have fewer spots we're returning
message_str?

[Alan Knight, 2013/03/14 17:49:05]

Done.

     _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);
+      var function = this[name];
+      if (function == null) return message_str;

[Emily Fortuna, 2013/03/13 18:54:43]

suggestion: instead of eagerly returning here, run the next line only if
(function != null), and then both code paths will hit line 104 (so you have
fewer "return message_str" branches

[Alan Knight, 2013/03/14 17:49:05]

Re-organized a bit more than even that so now there's only one "return
message_str" and result is initialized to message_str, so is used unless we
overwrite it it with the result of applying the message function.

+      result = Function.apply(function, args);
     } finally {
       _lookupInProgress = false;
     }
-    return result.then((value) => value.reflectee);
+    return result == null ? message_str : result;
   }
-}
+
+  operator [](x) => messages[x];
+
+  get messages;

[Emily Fortuna, 2013/03/13 18:54:43]

don't these need implementation? Return types? documentation?

[Alan Knight, 2013/03/14 17:49:05]

They are to be implemented by the generated subclasses. Added return types and
documentation.

[Emily Fortuna, 2013/03/14 19:45:00]

sgtm.

+
+  get localeName;
+
+  toString() => localeName;
+}