Handle field names of "descriptor" and "types".

[jskeet]

master equivalent of #662. Merging as that has an LG (when the build is green).

[agoodwin]

Hi @jskeet,

I just made a reference to this issue from this one: grpc/grpc#31590.

I was just wondering, do you remember (it's a long shot, I know) when you made this change why Types was a member name that needed to be handled?

I recently attempted to have a types property in one of my protobuf messages, but when I saw it being generated in C# with the _ suffix (Types_), I decided I'd prefer to find a different, slightly suboptimal name, rather than have the "ugliness" of the suffix.

Having said that, I couldn't see any reason why Types would have caused a naming collision, so I was curious if this is a case that doesn't actually need to be restricted? Was it just something needed e.g. with a previous version of protobuf?

I realise that even if it's no longer the case that it's needed, it's going to be an extremely low priority thing to change, and the ship has probably already sailed on that anyway as I guess it would be a breaking change now.

Still, if you do remember off the top of your head what this was needed for that'd be great, otherwise please feel to ignore this.

Thanks

[jskeet]

@agoodwin:

Having said that, I couldn't see any reason why Types would have caused a naming collision

Types is always used as a "holder" for nested messages and enums. For example, consider:

message Outer {
  message Nested {
  }
}

That generates (modulo partial etc):

public class Outer
{
    public class Types
    {
        public class Nested { }
    }
}

And we can't only add the suffix for a field if there happen to be no nested enums/messages at the moment, as otherwise adding a nested enum/message would become a breaking change.

[agoodwin]

Ah, thanks @jskeet, it is something fairly obvious then. I've just never made use of nested types so that's the obvious point I was missing.

And that makes total sense not to conditionally apply the suffix or anything complex like that as well. I shall stick with finding a more specific name than just types in the future, to avoid the suffix, and hopefully this conversation is useful to someone else in the future too.