In the past, if an endpoint defines a request DTO type, an accepts-metadata of application/json would be automatically added to the endpoint, which would require the user to clear that default metadata if all the properties of the DTO is bound from non-json binding sources such as route/query/header etc.

Now, if the user annotates all the properties of a DTO with the respective non-json binding sources such as the following:

sealed class GetAccountStatementRequest
{
    [RouteParam]
    public int UserId { get; set; }
    
    [QueryParam]
    public DateTime DateFrom { get; set; }

    [QueryParam]
    public DateTime DateTo { get; set; }
}

It is no longer necessary for the user to manually clear the default accepts-metadata as the presence of non-json binding source attributes on each of the DTO properties allows us to correctly detect that there's not going to be any JSON body present in the incoming request.

You can now annotate request DTO properties with DataAnnotations attributes such as [Required], [StringLength(...)] etc., instead of writing a FluentValidations validator for quick-n-dirty input validation. Do note however, only one of the strategies can be used for a single endpoint. I.e. if a request DTO has annotations as well as a fluent validator, only the fluent validator will be run and the annotations will be ignored. Mixing strategies is not allowed in order to prevent confusion for the reader. To enable DataAnnotations support, do the following:

app.UseFastEndpoints(c => c.Validation.EnableDataAnnotationsSupport = true)

A new feature introduced in v6.1 caused swagger generation to fail if the request DTO type of the endpoint is a List<T>, which has been corrected.

If a request uses a self referencing validator for nested properties, a stack overflow was happening due to infinite recursion.

Generic post-processors were not being correctly registered due to an oversight, which has been corrected with this release.

If a request DTO has required properties like so:

{
    public required string UserId { get; set; } //to be bound from route param
    public required string Name { get; set; } //to be bound from json body
}

The previous advice was to simply decorate the UserId property with a [JsonIgnore] attribute so that the serializer will ignore the required keyword and won't complain due to missing data for that property in the incoming JSON body.

Even though the [JsonIgnore] attribute seemed logical for this purpose at the time, we've come to realize it has the potential to cause problems elsewhere.

So, if you are using the required keyword on DTO properties that are to be bound from a non-json binding source such as route/query params, form fields, headers, claims, etc. and would like to keep on using the required keyword (even though it doesn't really make much sense in the context of request DTOs in most cases), you should remove the [JsonIgnore] property and annotate the binding related attribute that actually specifies what binding source should be used for that property, such as [RouteParam], [QueryParam], [FormField], [FromClaim], [FromHeader], etc.

The request DTO now needs to look like the following:

sealed class MyRequest
{
    [RouteParam]
    public required string UserId { get; set; }

    public required string Name { get; set; }
}