Improve error messages for invalid requests

pkg/analysis_server/tool/spec/codegen_dart_protocol.dart

 // Copyright (c) 2014, 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 codegen.protocol;
 
 import 'dart:convert';
 
 import 'package:html/dom.dart' as dom;
 
@@ skipping 331 matching lines @@
         writeln('} catch(_) {');
         indent(() {
           writeln('// Fall through');
         });
         writeln('}');
       });
       writeln('}');
       String humanReadableNameString =
           literalString(impliedType.humanReadableName);
       writeln(
-          'throw jsonDecoder.mismatch(jsonPath, $humanReadableNameString);');
+          'throw jsonDecoder.mismatch(jsonPath, $humanReadableNameString, json);');
     });
     writeln('}');
   }
 
   /**
    * Emit the class to encapsulate an object type.
    */
   void emitObjectClass(
       String className, TypeObject type, ImpliedType impliedType) {
     docComment(toHtmlVisitor.collectHtml(() {
@@ skipping 220 matching lines @@
         List<String> optionalArgs = <String>[];
         for (TypeObjectField field in type.fields) {
           String fieldNameString = literalString(field.name);
           String fieldAccessor = 'json[$fieldNameString]';
           String jsonPath = 'jsonPath + ${literalString('.${field.name}')}';
           if (field.value != null) {
             String valueString = literalString(field.value);
             writeln('if ($fieldAccessor != $valueString) {');
             indent(() {
               writeln(
-                  'throw jsonDecoder.mismatch(jsonPath, "equal " + $valueString);');
+                  'throw jsonDecoder.mismatch(jsonPath, "equal " + $valueString, json);');
             });
             writeln('}');
             continue;
           }
           if (isOptionalConstructorArg(className, field)) {
             optionalArgs.add('${field.name}: ${field.name}');
           } else {
             args.add(field.name);
           }
           TypeDecl fieldType = field.type;
@@ skipping 16 matching lines @@
           } else {
             writeln();
           }
         }
         args.addAll(optionalArgs);
         writeln('return new $className(${args.join(', ')});');
       });
       writeln('} else {');
       indent(() {
         writeln(
-            'throw jsonDecoder.mismatch(jsonPath, $humanReadableNameString);');
+            'throw jsonDecoder.mismatch(jsonPath, $humanReadableNameString, json);');
       });
       writeln('}');
     });
     writeln('}');
   }
 
   /**
    * Emit the hashCode getter for an object class.
    */
   void emitObjectHashCode(TypeObject type, String className) {
@@ skipping 582 matching lines @@
 
   @override
   String get asClosure => '($type value) => ${callback('value')}';
 
   @override
   bool get isIdentity => false;
 
   @override
   String asSnippet(String value) => callback(value);
 }