Allow translated messages that have no matching original message

pkg/intl/lib/generate_localized.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.
 
 /**
  * This provides utilities for generating localized versions of
  * messages. It does not stand alone, but expects to be given
  * TranslatedMessage objects and generate code for a particular locale
  * based on them.
  *
@@ skipping 68 matching lines @@
 
 /**
  * Generate a file messages_<locale>.dart for the [translations] in
  * [locale].
  */
 void generateIndividualMessageFile(String locale,
     Iterable<TranslatedMessage> translations, String targetDir) {
   var result = new StringBuffer();
   locale = new IntlMessage().escapeAndValidate(locale, locale);
   result.write(prologue(locale));
-  for (var each in translations) {
-    var message = each.originalMessage;
-    if (each.message != null) {
-      message.addTranslation(locale, each.message);
-    }
+  // Exclude messages with no translation and translations with no matching
+  // original message (e.g. if we're using some messages from a larger catalog)
+  var usableTranslations =  translations.where(
+      (each) => each.originalMessage != null && each.message != null).toList();
+  for (var each in usableTranslations) {
+      each.originalMessage.addTranslation(locale, each.message);
   }
-  var sorted = translations.where((each) => each.message != null).toList();
-  sorted.sort((a, b) =>
+  usableTranslations.sort((a, b) =>
       a.originalMessage.name.compareTo(b.originalMessage.name));
-  for (var each in sorted) {
+  for (var each in usableTranslations) {
     result.write("  ");
     result.write(each.originalMessage.toCode(locale));
     result.write("\n\n");
   }
   result.write("\n  final messages = const {\n");
-  var entries = sorted
+  var entries = usableTranslations
       .map((translation) => translation.originalMessage.name)
       .map((name) => "    \"$name\" : $name");
   result.write(entries.join(",\n"));
   result.write("\n  };\n}");
 
   var output = new File(path.join(targetDir,
       "${generatedFilePrefix}messages_$locale.dart"));
   output.writeAsStringSync(result.toString());
 }
 
@@ skipping 78 matching lines @@
   messageLookup.addLocale(localeName, _findGeneratedMessagesFor);
   return new Future.value();
 }
 
 MessageLookupByLibrary _findGeneratedMessagesFor(locale) {
   var actualLocale = Intl.verifiedLocale(locale, (x) => _findExact(x) != null);
   if (actualLocale == null) return null;
   return _findExact(actualLocale);
 }
 """;