HttpRepl Add nullable reference types

Since this is a .net core project, we have the opportunity to upgrade to C# 8 and make use of nullable reference types. I think we would benefit from enabling that and thus catching a certain class of errors that we saw a bit in our testing before the 3.0 release.

Jun 27 '20 22:06 tlmii

Since we've moved to C# 9 previews already, changing the title to reflect that we just need to add nullable reference types/annotations.

Oct 21 '20 09:10 tlmii

I'm going to defer this to post-5.0. I'd like it to be one of the first things we take up after that. But as I try to make the change, I keep bumping into small issues (like Microsoft.Repl being a netstandard2.0 assembly, and so it can't use the nullable reference type attributes without using something third party) and some things that are potentially disruptive changes. I also am curious how much of the existing parsing/commanding code will be cut when we do the System.CommandLine work. So I think it is better to defer this rather than rush it.

FYI @bradygaster

Nov 05 '20 19:11 tlmii