Getting hold of custom attribute property decorations in a Swashbuckle document filter - swagger

Question

I’m using Swashbuckle 6.1.4 in a .net 5.0 project.
I want to customise the ordering of the elements in a schema. The default order, i.e. that in which the properties are declared) isn’t good because when models extend a base model, the properties of the base model are listed at the bottom.
I’ve managed to apply a document filter to sort properties alphabetically:
public class SchemaSortingFilter : IDocumentFilter
{
public void Apply(OpenApiDocument swaggerDoc, DocumentFilterContext context)
{
var descs = context.ApiDescriptions.ToList();
// only applying to the SupporterDTO for now...
string model = "SupporterDTO";
if (swaggerDoc.Components.Schemas.ContainsKey(model))
{
var props = swaggerDoc.Components.Schemas[model].Properties.OrderBy(x => x.Key).ToArray();
swaggerDoc.Components.Schemas[model].Properties.Clear();
foreach (var prop in props)
{
swaggerDoc.Components.Schemas[model].Properties.Add(prop.Key, prop.Value);
}
}
}
}
But what I really want is to use a custom attribute to manage the order. Like this:
public class SwaggerOrderAttribute : Attribute
{
public int Order { get; private set; }
public SwaggerOrderAttribute(int order)
{
Order = order;
}
}
Which I’d use to decorate properties thus:
[SwaggerOrder(1)]
String PropertyZ {get; set;}
[SwaggerOrder(3)]
String PropertyX {get; set;}
[SwaggerOrder(2)]
String PropertyY {get; set;}
My problem is that the list of attribute values that is exposed in my filter via swaggerDoc.Components.Schemas[model].Properties does not include my custom attributes.
During my explorations, and thanks to a hint in this question I’ve tried to get hold of them like this but it didn’t see them:
if (apiDesc.TryGetMethodInfo(out MethodInfo mi))
{
var atts = mi.DeclaringType
.GetCustomAttributes(true)
.OfType<SwaggerOrderAttribute>()
.ToList();
}
How do I bring in my custom attributes for inclusion in my sorting linq query?

Answer 1

You need to implement ISchemaFilter. Then you'll be able to get hold of custom attributes from MemberInfo:
context.MemberInfo.CustomAttributes

Answer 2

Here is an implementation of getting an attribute from MemberInfo:
ISchemaFilter:
public class DefaultValuesSwaggerExtensions : Swashbuckle.AspNetCore.SwaggerGen.ISchemaFilter
{
public void Apply(OpenApiSchema schema, SchemaFilterContext context)
{
var attributes = context?.MemberInfo?.GetCustomAttributes(true).OfType<SwaggerDefaultValueAttribute>();
}
}
Swagger
services.AddSwaggerGen(c =>
{
c.SchemaFilter<DefaultValuesSwaggerExtensions>();
});