Improve error reporting on status page

pkg/analysis_server/lib/src/status/ast_writer.dart

Index: pkg/analysis_server/lib/src/status/ast_writer.dart
diff --git a/pkg/analysis_server/lib/src/status/ast_writer.dart b/pkg/analysis_server/lib/src/status/ast_writer.dart
index a5dd302da2b3c06d3077d7b558c8e45ced275f6a..97e9fa4eae46d824029ea9024b5260c9b54ee97a 100644
--- a/pkg/analysis_server/lib/src/status/ast_writer.dart
+++ b/pkg/analysis_server/lib/src/status/ast_writer.dart
@@ -7,6 +7,7 @@ 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.
@@ -23,6 +24,12 @@ class AstWriter extends UnifyingAstVisitor {
   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].
    */
@@ -174,9 +181,21 @@ class AstWriter extends UnifyingAstVisitor {
    */
   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>');
     }
   }