Make source map location information more readable.

pkg/source_maps/lib/span.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.
 
 /// Dart classes representing the souce spans and source files.
 library source_maps.span;
 
 import 'dart:math' show min, max;
 
+import 'package:path/path.dart' as p;
+
 import 'src/utils.dart';
 
 /// A simple class that describe a segment of source text.
 abstract class Span implements Comparable {
   /// The start location of this span.
   final Location start;
 
   /// The end location of this span, exclusive.
   final Location end;
 
@@ skipping 225 matching lines @@
       new String.fromCharCodes(_decodedChars.sublist(max(start, 0), end));
 
   /// Create a pretty string representation from a span.
   String getLocationMessage(String message, int start, int end,
       {bool useColors: false, String color}) {
     // TODO(jmesserly): it would be more useful to pass in an object that
     // controls how the errors are printed. This method is a bit too smart.
     var line = getLine(start);
     var column = getColumn(line, start);
 
-    var src = url == null ? '' : url;
-    var msg = '$src:${line + 1}:${column + 1}: $message';
+    var source = url == null ? '' : ' of ${p.prettyUri(url)}';
+    var msg = 'line ${line + 1}, column ${column + 1}$source: $message';
 
     if (_decodedChars == null) {
       // We don't have any text to include, so exit.
       return msg;
     }
 
     var buf = new StringBuffer(msg);
     buf.write('\n');
 
     // +1 for 0-indexing, +1 again to avoid the last line
@@ skipping 84 matching lines @@
   int getOffset(int line, int column) =>
     super.getOffset(line - _baseLine,
         line == _baseLine ? column - _baseColumn : column) + _baseOffset;
 
   /// Retrieve the text associated with the specified range. This method
   /// operates on the real offsets from the original file, so that error
   /// messages can be reported accurately.
   String getText(int start, [int end]) =>
     super.getText(start - _baseOffset, end == null ? null : end - _baseOffset);
 }