[Question] When NRT is added, should "Key(int index)" change as well?

[datvm]

This is a follow up of #205 . While making the changes of adding NRT to the project, I found an interesting change we may want to make as well: the KeyAsync(int index) method and its related functions. Right now it returns string? (null if the index is out of range). Should we:

• Keep it as it is right now (Javascript convention, a null is returned if the index is invalid).
  • Pros: Consistent with Javascript code. The result is returned as-is. No change is needed and no breaking change is introduced.
  • Cons: Developers are ended up with string? result which most of the time should not be null and a ! or ? operator or null check is needed.
• We throw IndexOutOfRangeException like most C# methods if the index is out of bound.
  • Pros: Consistent with C# convention. Most of the time developers do not have to worry about a null value if their code is sound.
  • Cons: Extra null or bound check for every function call. This is a breaking change.