SwaggerDefaultValues.cs

namespace Microsoft.Examples
{
    using Microsoft.AspNetCore.Mvc.ApiExplorer;
    using Microsoft.OpenApi.Models;
    using Swashbuckle.AspNetCore.SwaggerGen;
    using System.Linq;
    using System.Text.Json;

    /// <summary>
    /// Represents the Swagger/Swashbuckle operation filter used to document the implicit API version parameter.
    /// </summary>
    /// <remarks>This <see cref="IOperationFilter"/> is only required due to bugs in the <see cref="SwaggerGenerator"/>.
    /// Once they are fixed and published, this class can be removed.</remarks>
    public class SwaggerDefaultValues : IOperationFilter
    {
        /// <summary>
        /// Applies the filter to the specified operation using the given context.
        /// </summary>
        /// <param name="operation">The operation to apply the filter to.</param>
        /// <param name="context">The current operation filter context.</param>
        public void Apply( OpenApiOperation operation, OperationFilterContext context )
        {
            var apiDescription = context.ApiDescription;

            operation.Deprecated |= apiDescription.IsDeprecated();

            // REF: https://github.com/domaindrivendev/Swashbuckle.AspNetCore/issues/1752#issue-663991077
            foreach ( var responseType in context.ApiDescription.SupportedResponseTypes )
            {
                // REF: https://github.com/domaindrivendev/Swashbuckle.AspNetCore/blob/b7cf75e7905050305b115dd96640ddd6e74c7ac9/src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/SwaggerGenerator.cs#L383-L387
                var responseKey = responseType.IsDefaultResponse ? "default" : responseType.StatusCode.ToString();
                var response = operation.Responses[responseKey];

                foreach ( var contentType in response.Content.Keys )
                {
                    if ( !responseType.ApiResponseFormats.Any( x => x.MediaType == contentType ) )
                    {
                        response.Content.Remove( contentType );
                    }
                }
            }

            if ( operation.Parameters == null )
            {
                return;
            }

            // REF: https://github.com/domaindrivendev/Swashbuckle.AspNetCore/issues/412
            // REF: https://github.com/domaindrivendev/Swashbuckle.AspNetCore/pull/413
            foreach ( var parameter in operation.Parameters )
            {
                var description = apiDescription.ParameterDescriptions.First( p => p.Name == parameter.Name );

                if ( parameter.Description == null )
                {
                    parameter.Description = description.ModelMetadata?.Description;
                }

                if ( parameter.Schema.Default == null && description.DefaultValue != null )
                {
                    // REF: https://github.com/Microsoft/aspnet-api-versioning/issues/429#issuecomment-605402330
                    var json = JsonSerializer.Serialize( description.DefaultValue, description.ModelMetadata.ModelType );
                    parameter.Schema.Default = OpenApiAnyFactory.CreateFromJson( json );
                }

                parameter.Required |= description.IsRequired;
            }
        }
    }
}