Better handling of reading empty files

runtime/bin/file_impl.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.
 
 class _FileInputStream extends _BaseDataInputStream implements InputStream {
   _FileInputStream(String name)
       : _data = const [],
         _position = 0,
         _filePosition = 0 {
     var file = new File(name);
@@ skipping 674 matching lines @@
     }
     return new _FileOutputStream(_name, mode);
   }
 
   Future<List<int>> readAsBytes() {
     _ensureFileService();
     Completer<List<int>> completer = new Completer<List<int>>();
     var chunks = new _BufferList();
     var stream = openInputStream();
     stream.onClosed = () {
-      completer.complete(chunks.readBytes(chunks.length));
+      var result = chunks.readBytes(chunks.length);
+      if (result == null) result = <int>[];
+      completer.complete(result);
     };
     stream.onData = () {
       var chunk = stream.read();
       chunks.add(chunk);
     };
     stream.onError = completer.completeException;
     return completer.future;
   }
 
   List<int> readAsBytesSync() {
     var opened = openSync();
     var length = opened.lengthSync();
     var result = new Uint8List(length);
     var read = opened.readListSync(result, 0, length);
     if (read != length) {
       throw new FileIOException("Failed to read file");
     }
     opened.closeSync();
     return result;
   }
 
   Future<String> readAsText([Encoding encoding = Encoding.UTF_8]) {
     _ensureFileService();
     return readAsBytes().transform((bytes) {
+      if (bytes.length == 0) return "";
       var decoder = _StringDecoders.decoder(encoding);
       decoder.write(bytes);
       return decoder.decoded;
     });
   }
 
   String readAsTextSync([Encoding encoding = Encoding.UTF_8]) {
     var decoder = _StringDecoders.decoder(encoding);
     List<int> bytes = readAsBytesSync();
+    if (bytes.length == 0) return "";
     decoder.write(bytes);
     return decoder.decoded;
   }
 
   List<String> _getDecodedLines(_StringDecoder decoder) {
     List<String> result = [];
     var line = decoder.decodedLine;
     while (line != null) {
       result.add(line);
       line = decoder.decodedLine;
@@ skipping 422 matching lines @@
           new FileIOException("File closed '$_name'"));
     });
     return completer.future;
   }
 
   final String _name;
   int _id;
 
   SendPort _fileService;
 }