nullable annotations are still disabled for:
AstBuilder.cs
Token.cs

Motivation:

1. It required to do changes in Parser that is code generated and will require update BERP
2. AstBuilder.cs and Token.cs have potential a lot of "null pointer exception" problems that are hidden now. Fix will lead to changes that could be not so backward compatible

by this reason this is only initial support

Important:
This PR is a "source breaking change".
Nullable annotations could lead to new warnings in code that depends on this library.
For example if external code will try to pass null in not expected places.

functionally library is the same

please, during review, pay attention for all code base, not only changed files

motivation:

public abstract class StepsContainer(Location location, string keyword, string name, string description, Step[] steps)
    : IHasLocation, IHasDescription, IHasSteps
{
    public Location Location { get; } = location;
    public string Keyword { get; } = keyword;
    public string Name { get; } = name;
    public string Description { get; } = description;
    public IEnumerable<Step> Steps { get; } = steps;
}

should description be nullable here?

e your assistance in applying this same nullable annotations to the template that is used to generate the Io.Cucumber.Messages.Types classes.

hm, we have a separate library with copy-paste here?

please, during review, pay attention for all code base, not only changed files

motivation:

public abstract class StepsContainer(Location location, string keyword, string name, string description, Step[] steps)
    : IHasLocation, IHasDescription, IHasSteps
{
    public Location Location { get; } = location;
    public string Keyword { get; } = keyword;
    public string Name { get; } = name;
    public string Description { get; } = description;
    public IEnumerable<Step> Steps { get; } = steps;
}

should description be nullable here?

I'm really not sure. This part of the code base concerns the AST; I'm not knowledgable enough about that section to provide guidance. Gaspar is the expert to depend upon.

e your assistance in applying this same nullable annotations to the template that is used to generate the Io.Cucumber.Messages.Types classes.

hm, we have a separate library with copy-paste here?

I suspect its a result of how and when the libraries were built. They are not copy-paste, but parallel implementations of the same object model. The one you see in this library is a subset of that in the Cucumber.Messages library.

I've reviewed the DTOs created by the AstConverter against the schema for Messages and made a few comments where I found differences. The AstConverter is a limited implementation of Cucumber.Messages. Eventually we should port this over consuming the Cucumber.Messages types directly. @Romfos - would love to have your assistance in applying this same nullable annotations to the template that is used to generate the Io.Cucumber.Messages.Types classes.

cucumber/messages#253

Probably we need to reference them from Cucumber.Messages insted of have this non-compatible copy here

The latest version of messages has been released. Should be available on NuGet.

https://github.com/cucumber/messages/releases/tag/v26.0.1

ok, then lets put on hold, until cucumber messages are not updated with NRE