Recover from read errors.

dart/pkg/compiler/lib/src/source_file_provider.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.
 
 library source_file_provider;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import 'dart:math' as math;
@@ skipping 35 matching lines @@
       throw new ArgumentError("Unknown scheme in uri '$resourceUri'");
     }
   }
 
   Future<List<int>> _readFromFile(Uri resourceUri) {
     assert(resourceUri.scheme == 'file');
     List<int> source;
     try {
       source = readAll(resourceUri.toFilePath());
     } on FileSystemException catch (ex) {
+      OSError ose = ex.osError;
+      String detail = (ose != null && ose.message != null)
+          ? ' (${ose.message})'
+          : '';
       return new Future.error(
-          "Error reading '${relativize(cwd, resourceUri, isWindows)}' "
-          "(${ex.osError})");
+          "Error reading '${relativize(cwd, resourceUri, isWindows)}'"
+          "$detail");
     }
     dartCharactersRead += source.length;
     sourceFiles[resourceUri.toString()] =
         new CachingUtf8BytesSourceFile(relativizeUri(resourceUri), source);
     return new Future.value(source);
   }
 
   Future<List<int>> _readFromHttp(Uri resourceUri) {
     assert(resourceUri.scheme == 'http');
     HttpClient client = new HttpClient();
@@ skipping 127 matching lines @@
       color = (x) => x;
     }
     if (uri == null) {
       print('${color(message)}');
     } else {
       SourceFile file = provider.sourceFiles[uri.toString()];
       if (file != null) {
         print(file.getLocationMessage(
           color(message), begin, end, colorize: color));
       } else {
-        print('${provider.relativizeUri(uri)}@$begin+${end - begin}:'
-              ' [$kind] ${color(message)}');
+        String position = end - begin > 0 ? '@$begin+${end - begin}' : '';
+        print('${provider.relativizeUri(uri)}$position:\n'
+              '${color(message)}');
       }
     }
     if (fatal && ++fatalCount >= throwOnErrorCount && throwOnError) {
       isAborting = true;
       throw new AbortLeg(message);
     }
   }
 
   void call(Uri uri, int begin, int end, String message, api.Diagnostic kind) {
     return diagnosticHandler(uri, begin, end, message, kind);
@@ skipping 100 matching lines @@
   var onAdd, onClose;
 
   EventSinkWrapper(this.onAdd, this.onClose);
 
   void add(String data) => onAdd(data);
 
   void addError(error, [StackTrace stackTrace]) => throw error;
 
   void close() => onClose();
 }