This comment was originally written by bordol...@gmail.com

Another oddity is the spec for iterator, which requires that Iterator.current return null if empty.moveNext() returns false. Conceptually it seems like the api would be easier to grok, if Iterator was defined such that current always returns null until moveNext() is called at least once returning true, and that current retains its last value if moveNext() returns false.

Changing the Iterator spec as such, would then allow RuneIterator.rawIndex to always return the last value up to String.length -1;

This comment was originally written by bordo...@gmail.com

I also think, that rawIndex should be defined to return -1, if moveNext() has not yet been called. Consider the following example:

part of restlib.parsing_test;

main() {
  String parse(RuneIterator itr) {
    int startIndex = itr.rawIndex; // startIndex is null
    while(itr.moveNext() && itr.current != "d".runes.single) {
      // keep reading characters
    }
    if (itr.rawIndex > startIndex) { // oops comparing int to null,
                                     // noSuchMethodException for example 2
      return itr.string.substring(startIndex + 1, itr.rawIndex);
    } else {
      return "";
    }
  };
  
  RuneIterator itr1 = "abcd".runes.iterator;
  itr1.moveNext();
  print ("result: ${parse(itr1)}");
  
  RuneIterator itr2 = "abcd".runes.iterator;
  print ("result: ${parse(itr2)}"); // crashes
}

This comment was originally written by bordol...@gmail.com

I ended up writing my own StringIterator class. I retained the behavior of honoring the null contract for Iterator.current, but changed the rawIndex field to always return an int between -1 and string.length. This would be my recommendation for dart as well to avoid the need for lots of special null handling when interacting with RuneIterator.

This comment was originally written by bordol...@gmail.com

https://code.google.com/p/dart-restlib/source/browse/lib/src/parsing/string_iterator.dart

Removed Type-Defect label.
Added Type-Enhancement, Area-Library, Library-Core, Triaged labels.

Fwiw, this is a contentious issue and being actively discussed.