Swagger versioning is not working. It displays all endpoints, despite the selected API version

Question

all!

I am using Swagger in ASP.NET Core 3.1 application.

I need to create an endpoint for the new version of API and with the same route as a previous version.

My controller is:

namespace Application.Controllers
{
    [ApiVersion("1")]
    [ApiVersion("2")]
    [ApiController]
    [Route("api/v{version:apiVersion}")]
    public class CustomController: ControllerBase
    {
        [HttpGet]
        [Route("result")]
        public IActionResult GetResult()
        {
            return Ok("v1")
        }

        [HttpGet]
        [MapToApiVersion("2")]
        [Route("result")]
        public IActionResult GetResult(int number)
        {
            return Ok("v2")
        }
    }
}

My configuration:

            services.AddApiVersioning(
                options =>
                {
                    options.ReportApiVersions = true;
                });

            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc($"v1", new OpenApiInfo { Title = "api1", Version = $"v1" });

                c.SwaggerDoc($"v2", new OpenApiInfo { Title = "api2", Version = $"v2" });         
         

                c.OperationFilter<RemoveVersionParameterFilter>();
                c.DocumentFilter<ReplaceVersionWithExactValueInPathFilter>();
                c.EnableAnnotations();
            });

app.UseSwagger().UseSwaggerUI(c =>
            {
                c.SwaggerEndpoint($"/swagger/v1/swagger.json", $"api1 v1");
                c.SwaggerEndpoint($"/swagger/v2/swagger.json", $"api2 v2");
            });

After loading I get an error: Fetch error undefined /swagger/v1/swagger.json But If I change the second route to the "resutlTwo", I can observe both endpoints in swagger, ignoring current version (api1 v1 or api2 v2)

How can I see only 1 endpoint per API version?

Answer 1

I just tested your case with this setup.You are missing UrlSegmentApiVersionReader.

public class SwaggerOptions
{
    public string Title { get; set; }
    public string JsonRoute { get; set; }
    public string Description { get; set; }
    public List<Version> Versions { get; set; }

    public class Version
    {
        public string Name { get; set; }
        public string UiEndpoint { get; set; }
    }
}

In Startup#ConfigureServices

        // Configure versions 
        services.AddApiVersioning(apiVersioningOptions =>
        {
            apiVersioningOptions.ReportApiVersions = true;
            apiVersioningOptions.ApiVersionReader = new UrlSegmentApiVersionReader();
        });

        // Register the Swagger generator, defining 1 or more Swagger documents
        services.AddSwaggerGen(swaggerGenOptions =>
        {
            var swaggerOptions = new SwaggerOptions();
            Configuration.GetSection("Swagger").Bind(swaggerOptions);

            foreach (var currentVersion in swaggerOptions.Versions)
            {
                swaggerGenOptions.SwaggerDoc(currentVersion.Name, new OpenApiInfo
                {
                    Title = swaggerOptions.Title,
                    Version = currentVersion.Name,
                    Description = swaggerOptions.Description
                });
            }

            swaggerGenOptions.DocInclusionPredicate((version, desc) =>
            {
                if (!desc.TryGetMethodInfo(out MethodInfo methodInfo))
                {
                    return false;
                }
                var versions = methodInfo.DeclaringType.GetConstructors()
                    .SelectMany(constructorInfo => constructorInfo.DeclaringType.CustomAttributes
                        .Where(attributeData => attributeData.AttributeType == typeof(ApiVersionAttribute))
                        .SelectMany(attributeData => attributeData.ConstructorArguments
                            .Select(attributeTypedArgument => attributeTypedArgument.Value)));

                return versions.Any(v => $"{v}" == version);
            });

            swaggerGenOptions.IncludeXmlComments(Path.Combine(AppContext.BaseDirectory, $"{Assembly.GetExecutingAssembly().GetName().Name}.xml"));
            
            ... some filter settings here 
        });

In Startup#Configure

var swaggerOptions = new SwaggerOptions();
Configuration.GetSection("Swagger").Bind(swaggerOptions);
app.UseSwagger(option => option.RouteTemplate = swaggerOptions.JsonRoute);

app.UseSwaggerUI(option =>
{
  foreach (var currentVersion in swaggerOptions.Versions)
  {
    option.SwaggerEndpoint(currentVersion.UiEndpoint, $"{swaggerOptions.Title} {currentVersion.Name}");
  }
});

appsettings.json

{
  "Swagger": {
    "Title": "App title",
    "JsonRoute": "swagger/{documentName}/swagger.json",
    "Description": "Some text",
    "Versions": [
      {
        "Name": "2.0",
          "UiEndpoint": "/swagger/2.0/swagger.json"
      },
      {
        "Name": "1.0",
        "UiEndpoint": "/swagger/1.0/swagger.json"
      }
    ]
  }
}

This code is very similar to a related issue I'm working on here on SO.