Pass through context information in error messages

lib/runtime/messages_widget.dart

 // Copyright (c) 2015, 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 library provides a single function called injectLogs which when called
 /// will request a logs json file and build a small widget out of them which
 /// groups the logs by level.
 library polymer.build.log_injector;
 
 import 'dart:async';
@@ skipping 37 matching lines @@
 
     // TODO(sigmund): add permanent links to error messages like in polymer.
     for (var m in messages) {
       var message = _hyperlinkUrls(_escape(m.message));
       var span = m.span;
       var sb = new StringBuffer();
       sb.write('<div class="message"><div class="text $level">$message</div>');
       if (span != null) {
         sb.write('<div class="location">'
             '  <span class="location">${span.start.toolString}</span></div>'
-            '  <span class="text">${_escape(span.text)}</span></div></div>');
+            '  <span class="text">');
+        if (span is SourceSpanWithContext) {
+          var context = span.context;
+          var text = span.text;
+          sb.write(_escape(context.substring(0, span.start.column)));
+          sb.write('<span class="$level">');
+          sb.write(_escape(span.text));
+          sb.write('</span>');
+          sb.write(_escape(context.substring(span.end.column)));
+        } else {
+          sb.write(_escape(span.text));
+        }
+        sb.write('</span></div></div>');
       }
       sb.write('</div>');
 
       var logElement = new Element.html('$sb',
           validator: new NodeValidatorBuilder.common()
         ..allowNavigation(new _OpenUriPolicy()));
       contentItem.append(logElement);
       var messageElement = logElement.querySelector('div.text');
       messageElement.onClick.listen((e) {
         if (e.target == messageElement) {
@@ skipping 42 matching lines @@
 class _Visitor extends RecursiveSummaryVisitor {
   final Map<String, List<MessageSummary>> messagesByLevel = {};
 
   @override
   void visitMessage(MessageSummary message) {
     var level = message.level.toLowerCase();
     messagesByLevel.putIfAbsent(level, () => []);
     messagesByLevel[level].add(message);
   }
 }