SwaggerDefaultValues.cs

namespace ApiVersioning.Examples;

using Microsoft.AspNetCore.Mvc.ApiExplorer;
using Microsoft.OpenApi.Models;
using Swashbuckle.AspNetCore.SwaggerGen;
using System.Text.Json;

/// <summary>
/// Represents the OpenAPI/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 );

            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;
        }
    }
}