Improve error reporting on status page

pkg/analysis_server/lib/src/status/ast_writer.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.
 
 library analysis_server.src.status.ast_writer;
 
 import 'dart:convert';
 
 import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/java_engine.dart';
 
 /**
  * A visitor that will produce an HTML representation of an AST structure.
  */
 class AstWriter extends UnifyingAstVisitor {
   /**
    * The buffer on which the HTML is to be written.
    */
   final StringBuffer buffer;
 
   /**
    * The current level of indentation.
    */
   int indentLevel = 0;
 
   /**
+   * A list containing the exceptions that were caught while attempting to write
+   * out an AST structure.
+   */
+  List<CaughtException> exceptions = <CaughtException>[];
+
+  /**
    * Initialize a newly created element writer to write the HTML representation
    * of visited nodes on the given [buffer].
    */
   AstWriter(this.buffer);
 
   @override
   void visitNode(AstNode node) {
     _writeNode(node);
     indentLevel++;
     try {
@@ skipping 131 matching lines @@
       _writeProperty('static type', node.staticType);
       _writeProperty('propagated type', node.propagatedType);
     }
   }
 
   /**
    * Write the [value] of the property with the given [name].
    */
   void _writeProperty(String name, Object value) {
     if (value != null) {
+      String valueString = null;
+      try {
+        valueString = value.toString();
+      } catch (exception, stackTrace) {
+        exceptions.add(new CaughtException(exception, stackTrace));
+      }
       _indent(2);
       buffer.write('$name = ');
-      buffer.write(HTML_ESCAPE.convert(value.toString()));
+      if (valueString == null) {
+        buffer.write('<span style="color: #FF0000">');
+        buffer.write(HTML_ESCAPE.convert(value.runtimeType.toString()));

[Paul Berry, 2015/02/02 23:08:59]

Nit: this will print "Null" in red whenever an error occurs.  That might be a
little bit confusing.  How about instead printing the runtimeType of the
exception in red?

[Brian Wilkerson, 2015/02/02 23:25:03]

Why? The value of 'value' is known to be non-null, so why wouldn't this print
the runtime type of the value?

[Paul Berry, 2015/02/02 23:32:27]

Sorry, I misread the code.  lgtm as is.

+        buffer.write('</span>');
+      } else {
+        buffer.write(HTML_ESCAPE.convert(valueString));
+      }
       buffer.write('<br>');
     }
   }
 }