Add optional arguments to NullPointerException so that it can report more information (make it simi…

corelib/src/exceptions.dart

 // Copyright (c) 2012, 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.
 
 // Exceptions are thrown either by the VM or from Dart code.
 
 /**
  * Interface implemented by all core library exceptions.
  */
 interface Exception default ExceptionImplementation {
@@ skipping 103 matching lines @@
 }
 
 
 class WrongArgumentCountException implements Exception {
   const WrongArgumentCountException();
   String toString() => "WrongArgumentCountException";
 }
 
 
 class NullPointerException implements Exception {
-  const NullPointerException();
-  String toString() => "NullPointerException";
+  const NullPointerException([this.functionName,
+                              this.arguments = const[]]);

[sra1, 2012/04/11 20:43:12]

NullPointerException is called from hand written JS code in the Frog runtime.
Calling from hand written JS code has a constraint that optional argument
default values can only be null.
It is not possible in the hand-written code to find the 'global' variable
containing the shared const empty list.

It might be possible to change the call in the hand written code to explicitly
pass null and [].

+  String toString() {
+    StringBuffer sb = new StringBuffer();
+    for (var arg in arguments) {
+      if (!sb.isEmpty()) sb.add(", ");
+      sb.add(arg);
+    }
+    if (functionName == null) {

[sra1, 2012/04/11 20:43:12]

Do this test first.  No need to allocate a StringBuffer if you don't use it.

+      return exceptionName;
+    } else {
+      return "$exceptionName : method: '$functionName'\n"
+          "Receiver: null\n"
+          "Arguments: [$sb]";
+    }
+  }
+  
+  String get exceptionName() => "NullPointerException";
+
+  final String functionName;
+  final List arguments;
 }
 
 
 class NoMoreElementsException implements Exception {
   const NoMoreElementsException();
   String toString() => "NoMoreElementsException";
 }
 
 
 class EmptyQueueException implements Exception {
@@ skipping 20 matching lines @@
   String toString() => "IllegalJSRegExpException: '$_pattern' '$_errmsg'";
   final String _pattern;
   final String _errmsg;
 }
 
 
 class IntegerDivisionByZeroException implements Exception {
   const IntegerDivisionByZeroException();
   String toString() => "IntegerDivisionByZeroException";
 }