Comments and nullable context

XML documentation

Types and members have XmlComments. AddSummary, AddParam, AddTypeParam and AddReturn add the common elements, and Add(XElement) any other element. Statements have CommentsBefore and CommentsAfter, which write line comments:

var method = new MethodDeclaration("Greet")
{
    Modifiers = Modifiers.Public,
    ReturnType = typeof(string),
};
var name = method.AddArgument("name", typeof(string));
method.XmlComments.AddSummary("Creates a greeting message.");
method.XmlComments.AddParam("name", "The name of the person to greet.");

var statement = new ReturnStatement(Expression.Add("Hello ", name));
statement.CommentsBefore.Add("Keep the message short");
method.Statements = statement;

The method is written as:

/// <summary>Creates a greeting message.</summary>
/// <param name="name">The name of the person to greet.</param>
public string Greet(string name)
{
    // Keep the message short
    return ("Hello " + name);
}

A CommentStatement is a comment on its own line among the statements. Expressions, declarations and other code objects have CommentsBefore and CommentsAfter too. The comments of an expression are inline comments (/* ... */) by default; Add(text, CommentType) chooses the kind of each comment.

Nullable reference types

Set NullableContext on a compilation unit, a type, a member or a statement to write a #nullable directive, and use MakeNullable() to annotate a reference type:

var unit = new CompilationUnit
{
    NullableContext = NullableContext.Enable,
};
var type = unit.AddNamespace("Demo").AddType(new ClassDeclaration("Person"));
type.AddMember(new FieldDeclaration("_nickname", new TypeReference(typeof(string)).MakeNullable()));

Assert.Equal("""
    #nullable enable
    namespace Demo
    {
        class Person
        {
            string? _nickname;
        }
    }

    """, unit.ToCsharpString());

NullableContext.Enable writes #nullable enable and Disable writes #nullable disable. Default writes nothing. On a type, a member or a statement, the opposite directive follows the object, so the setting applies to that object only.