Inconsistent behavior between positive indices and negative indices.

the same method normaliseIndex is used both for putAt & getAt. An ArrayIndexOutOfBoundsException
have to be thrown for getAt when index is greater than size.

The behavior can be explained as follows:

lists/collections:

• negative index can't be greater that collection size
• positive index may be greater that collection size, yielding null because of

  def list = []
  list[100] = "ok"
  assert list[50] == null
  assert list.size() == 101
  assert list[-100] == null
  try{ list[-101] == null }
  catch( ArrayIndexOutOfBoundsException expected ) { /*ok!*/}

arrays:

• negative and positive index can't be greater than the size of the array, as arrays have a fixed length

strings:

• negative and positive index can't be greater than the size of the string as strings have a fixed length

Because this issue was reported against Lists I think it can be closed as "Not an Issue".

In hindsight, is it not a slightly odd decision to go with this behaviour?

Take the following output from groovy console:

groovy> def o = [name:'A'] 
groovy> def lineage = [o] 
groovy> Object[] lineageArray = [o] 
groovy> def index = 0 
groovy> println lineage[index++] 
groovy> println lineage[index++] 
groovy> index = 0 
groovy> println lineageArray[index++] 
groovy> println lineageArray[index++] 
 
[name:A]
null
[name:A]
Exception thrown
Oct 25, 2010 2:29:11 PM org.codehaus.groovy.runtime.StackTraceUtils sanitize
WARNING: Sanitizing stacktrace:
java.lang.ArrayIndexOutOfBoundsException: 1

Did we really want this divergent behaviour? Surely getAt on lists should throw AIOOB but putAt shouldn't.

your example does not contain a putAt that throws an exception.