Add Description Attribute to JsonSchema.Net.Generation

[DanielHabenicht]

Environment

• Nuget Package: JsonSchema.Net.Generation
• Nuget Version: 1.7.1
• OS: Windows
• .Net Target: Core 5

Can this library make doing something simpler?
A common use case is to add Descriptions to an Property:

        [Description("The title of the event.")]
        public string Title { get; init; }

It would be great if json-everything would support this out of the box.

Describe alternatives you've considered
Implement it yourself, e.g.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Json.Schema;
using Json.Schema.Generation;

namespace EnoCore.Models.Schema
{
    [AttributeUsage(AttributeTargets.Property)]
    public class Description : Attribute, IAttributeHandler
    {
        public string Value { get; }

        public Description(string value)
        {
            Value = value;
        }

        void IAttributeHandler.AddConstraints(SchemaGeneratorContext context)
        {
            var attribute = context.Attributes.OfType<Description>().FirstOrDefault();
            if (attribute == null) return;

            context.Intents.Add(new DescriptionIntent(attribute.Value));
        }
    }

    public class DescriptionIntent : ISchemaKeywordIntent
    {
        public string Description { get; private set; }

        public DescriptionIntent(string description)
        {
            Description = description;
        }

        public void Apply(JsonSchemaBuilder builder) => builder.Description(this.Description);
    }
}

Additional context
I am happy to make a PR

[gregsdennis]

This is a good addition. We should probably add

• title
• default

as well. These and examples make up the metadata keywords. Not sure how examples would do as an attribute, though.

(deprecated is actually handled by [Obsolete] currently)

---

The only reason I didn't put these in at first was that they don't do anything for validation, which I figured was the primary purpose for generating a schema.

[DanielHabenicht]

ok, I will come up with a PR next weekend.

By the way is there a way to use the maybe already specified Attributes from System.ComponentModel.DataAnnotations (e.g. Required or [Range(minimum: 0, maximum: 2)])?

[gregsdennis]

Required is already supported, and I already have Minimum and Maximum defined. I think these are more explicit.

Additionally, I found a StackOverflow question where they didn't want to use JsonIgnore because it interfered with using the same model for serialization. As such, I think it's good to have explicitly defined attributes.

I think what I'm going to do is add an option to enable DataAnnotations support. I can then support things like Range when that's turned on.

Don't worry about a PR, I've got it. Thanks.

[gregsdennis]

I've opened #143 for the DataAnnotations support. It's a bit more complex than just adding them.