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

corelib/src/exceptions.dart

Index: corelib/src/exceptions.dart
===================================================================
--- corelib/src/exceptions.dart	(revision 6423)
+++ corelib/src/exceptions.dart	(working copy)
@@ -121,8 +121,27 @@
 
 
 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;
 }