Swashbuckle IDocumentFilter that only includes attributed classes. This is good for documenting message bus messages

ContractAttribute.cs

using System;

[AttributeUsageAttribute(AttributeTargets.Class, Inherited = true, AllowMultiple = false)]
public class ContractAttribute : Attribute {}

ContractOnlyFilter.cs

public class ContractOnlyFilter : IDocumentFilter
{
    public void Apply(SwaggerDocument swaggerDoc, DocumentFilterContext context)
    {
        // however you identify the version of your messages
        if (swaggerDoc.Info.Version.Contains("message"))
        {
            swaggerDoc.Paths.Clear();
            swaggerDoc.Definitions.Clear();
            var contracts = Assembly.GetExecutingAssembly().GetTypes().Where(x => x.GetCustomAttributes(true).Any(a => a.GetType() == typeof(ContractAttribute)));
            foreach (var contract in contracts)
            {
                context.SchemaRegistry.GetOrRegister(contract);
            }
        }
    }
}