Add support for async filters

src/Swashbuckle.AspNetCore.Cli/Program.cs

@@ -32,15 +32,19 @@ public static int Main(string[] args)
             {
                 c.Argument("startupassembly", "relative path to the application's startup assembly");
                 c.Argument("swaggerdoc", "name of the swagger doc you want to retrieve, as configured in your startup class");
+
                 c.Option("--output", "relative path where the Swagger will be output, defaults to stdout");
                 c.Option("--host", "a specific host to include in the Swagger output");
                 c.Option("--basepath", "a specific basePath to include in the Swagger output");
                 c.Option("--serializeasv2", "output Swagger in the V2 format rather than V3", true);
                 c.Option("--yaml", "exports swagger in a yaml format", true);
+
                 c.OnRun((namedArgs) =>
                 {
                     if (!File.Exists(namedArgs["startupassembly"]))
+                    {
                         throw new FileNotFoundException(namedArgs["startupassembly"]);
+                    }
 
                     var depsFile = namedArgs["startupassembly"].Replace(".dll", ".deps.json");
                     var runtimeConfig = namedArgs["startupassembly"].Replace(".dll", ".runtimeconfig.json");
@@ -110,37 +114,42 @@ public static int Main(string[] args)
                         }
                     }
 
-                    using (Stream stream = outputPath != null ? File.Create(outputPath) : Console.OpenStandardOutput())
-                    using (var streamWriter = new FormattingStreamWriter(stream, CultureInfo.InvariantCulture))
+                    using Stream stream = outputPath != null ? File.Create(outputPath) : Console.OpenStandardOutput();
+                    using var streamWriter = new FormattingStreamWriter(stream, CultureInfo.InvariantCulture);
+
+                    IOpenApiWriter writer;
+                    if (namedArgs.ContainsKey("--yaml"))
                     {
-                        IOpenApiWriter writer;
-                        if (namedArgs.ContainsKey("--yaml"))
-                            writer = new OpenApiYamlWriter(streamWriter);
-                        else
-                            writer = new OpenApiJsonWriter(streamWriter);
+                        writer = new OpenApiYamlWriter(streamWriter);
+                    }
+                    else
+                    {
+                        writer = new OpenApiJsonWriter(streamWriter);
+                    }
 
-                        if (namedArgs.ContainsKey("--serializeasv2"))
-                        {
-                            if (swaggerDocumentSerializer != null)
-                            {
-                                swaggerDocumentSerializer.SerializeDocument(swagger, writer, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi2_0);
-                            }
-                            else
-                            {
-                                swagger.SerializeAsV2(writer);
-                            }
-                        }
-                        else if (swaggerDocumentSerializer != null)
+                    if (namedArgs.ContainsKey("--serializeasv2"))
+                    {
+                        if (swaggerDocumentSerializer != null)
                         {
-                            swaggerDocumentSerializer.SerializeDocument(swagger, writer, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi3_0);
+                            swaggerDocumentSerializer.SerializeDocument(swagger, writer, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi2_0);
                         }
                         else
                         {
-                            swagger.SerializeAsV3(writer);
+                            swagger.SerializeAsV2(writer);
                         }
+                    }
+                    else if (swaggerDocumentSerializer != null)
+                    {
+                        swaggerDocumentSerializer.SerializeDocument(swagger, writer, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi3_0);
+                    }
+                    else
+                    {
+                        swagger.SerializeAsV3(writer);
+                    }
 
-                        if (outputPath != null)
-                            Console.WriteLine($"Swagger JSON/YAML successfully written to {outputPath}");
+                    if (outputPath != null)
+                    {
+                        Console.WriteLine($"Swagger JSON/YAML successfully written to {outputPath}");
                     }
 
                     return 0;
@@ -152,7 +161,7 @@ public static int Main(string[] args)
 
         private static string EscapePath(string path)
         {
-            return path.Contains(" ")
+            return path.Contains(' ')
                 ? "\"" + path + "\""
                 : path;
         }
@@ -200,23 +209,26 @@ private static bool TryGetCustomHost<THost>(
                 .Where(t => t.Name == factoryClassName)
                 .ToList();
 
-            if (!factoryTypes.Any())
+            if (factoryTypes.Count == 0)
             {
                 host = default;
                 return false;
             }
-
-            if (factoryTypes.Count() > 1)
+            else if (factoryTypes.Count > 1)
+            {
                 throw new InvalidOperationException($"Multiple {factoryClassName} classes detected");
+            }
 
             var factoryMethod = factoryTypes
                 .Single()
                 .GetMethod(factoryMethodName, BindingFlags.Public | BindingFlags.Static);
 
             if (factoryMethod == null || factoryMethod.ReturnType != typeof(THost))
+            {
                 throw new InvalidOperationException(
                     $"{factoryClassName} class detected but does not contain a public static method " +
                     $"called {factoryMethodName} with return type {typeof(THost).Name}");
+            }
 
             host = (THost)factoryMethod.Invoke(null, null);
             return true;

src/Swashbuckle.AspNetCore.Swagger/IAsyncSwaggerProvider.cs

@@ -1,3 +1,4 @@
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.OpenApi.Models;
 
@@ -8,6 +9,7 @@ public interface IAsyncSwaggerProvider
         Task<OpenApiDocument> GetSwaggerAsync(
             string documentName,
             string host = null,
-            string basePath = null);
+            string basePath = null,
+            CancellationToken cancellationToken = default);
     }
-}
+}

src/Swashbuckle.AspNetCore.Swagger/SwaggerMiddleware.cs

@@ -1,5 +1,4 @@
-using System;
-using System.Globalization;
+using System.Globalization;
 using System.IO;
 using System.Text;
 using System.Threading.Tasks;
@@ -57,17 +56,23 @@ public async Task Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvid
                     ? httpContext.Request.PathBase.Value
                     : null;
 
-                var swagger = swaggerProvider switch
+                OpenApiDocument swagger;
+                var asyncSwaggerProvider = httpContext.RequestServices.GetService<IAsyncSwaggerProvider>();
+
+                if (asyncSwaggerProvider is not null)
                 {
-                    IAsyncSwaggerProvider asyncSwaggerProvider => await asyncSwaggerProvider.GetSwaggerAsync(
+                    swagger = await asyncSwaggerProvider.GetSwaggerAsync(
                         documentName: documentName,
                         host: null,
-                        basePath: basePath),
-                    _ => swaggerProvider.GetSwagger(
+                        basePath: basePath);
+                }
+                else
+                {
+                    swagger = swaggerProvider.GetSwagger(
                         documentName: documentName,
                         host: null,
-                        basePath: basePath)
-                };
+                        basePath: basePath);
+                }
 
                 // One last opportunity to modify the Swagger Document - this time with request context
                 foreach (var filter in _options.PreSerializeFilters)
@@ -123,7 +128,7 @@ private bool RequestingSwaggerDocument(HttpRequest request, out string documentN
             return false;
         }
 
-        private void RespondWithNotFound(HttpResponse response)
+        private static void RespondWithNotFound(HttpResponse response)
         {
             response.StatusCode = 404;
         }
@@ -133,53 +138,50 @@ private async Task RespondWithSwaggerJson(HttpResponse response, OpenApiDocument
             response.StatusCode = 200;
             response.ContentType = "application/json;charset=utf-8";
 
-            using (var textWriter = new StringWriter(CultureInfo.InvariantCulture))
+            using var textWriter = new StringWriter(CultureInfo.InvariantCulture);
+            var jsonWriter = new OpenApiJsonWriter(textWriter);
+
+            if (_options.SerializeAsV2)
             {
-                var jsonWriter = new OpenApiJsonWriter(textWriter);
-                if (_options.SerializeAsV2)
-                {
-                    if (_options.CustomDocumentSerializer != null)
-                        _options.CustomDocumentSerializer.SerializeDocument(swagger, jsonWriter, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi2_0);
-                    else
-                        swagger.SerializeAsV2(jsonWriter);
-                }
+                if (_options.CustomDocumentSerializer != null)
+                    _options.CustomDocumentSerializer.SerializeDocument(swagger, jsonWriter, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi2_0);
                 else
-                {
-                    if (_options.CustomDocumentSerializer != null)
-                        _options.CustomDocumentSerializer.SerializeDocument(swagger, jsonWriter, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi3_0);
-                    else
-                        swagger.SerializeAsV3(jsonWriter);
-                }
-
-                await response.WriteAsync(textWriter.ToString(), new UTF8Encoding(false));
+                    swagger.SerializeAsV2(jsonWriter);
+            }
+            else
+            {
+                if (_options.CustomDocumentSerializer != null)
+                    _options.CustomDocumentSerializer.SerializeDocument(swagger, jsonWriter, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi3_0);
+                else
+                    swagger.SerializeAsV3(jsonWriter);
             }
+
+            await response.WriteAsync(textWriter.ToString(), new UTF8Encoding(false));
         }
 
         private async Task RespondWithSwaggerYaml(HttpResponse response, OpenApiDocument swagger)
         {
             response.StatusCode = 200;
             response.ContentType = "text/yaml;charset=utf-8";
 
-            using (var textWriter = new StringWriter(CultureInfo.InvariantCulture))
+            using var textWriter = new StringWriter(CultureInfo.InvariantCulture);
+            var yamlWriter = new OpenApiYamlWriter(textWriter);
+            if (_options.SerializeAsV2)
             {
-                var yamlWriter = new OpenApiYamlWriter(textWriter);
-                if (_options.SerializeAsV2)
-                {
-                    if (_options.CustomDocumentSerializer != null)
-                        _options.CustomDocumentSerializer.SerializeDocument(swagger, yamlWriter, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi2_0);
-                    else
-                        swagger.SerializeAsV2(yamlWriter);
-                }
+                if (_options.CustomDocumentSerializer != null)
+                    _options.CustomDocumentSerializer.SerializeDocument(swagger, yamlWriter, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi2_0);
                 else
-                {
-                    if (_options.CustomDocumentSerializer != null)
-                        _options.CustomDocumentSerializer.SerializeDocument(swagger, yamlWriter, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi3_0);
-                    else
-                        swagger.SerializeAsV3(yamlWriter);
-                }
-
-                await response.WriteAsync(textWriter.ToString(), new UTF8Encoding(false));
+                    swagger.SerializeAsV2(yamlWriter);
             }
+            else
+            {
+                if (_options.CustomDocumentSerializer != null)
+                    _options.CustomDocumentSerializer.SerializeDocument(swagger, yamlWriter, Microsoft.OpenApi.OpenApiSpecVersion.OpenApi3_0);
+                else
+                    swagger.SerializeAsV3(yamlWriter);
+            }
+
+            await response.WriteAsync(textWriter.ToString(), new UTF8Encoding(false));
         }
     }
 }

src/Swashbuckle.AspNetCore.SwaggerGen/DependencyInjection/ConfigureSwaggerGeneratorOptions.cs

@@ -68,9 +68,13 @@ public void DeepCopy(SwaggerGeneratorOptions source, SwaggerGeneratorOptions tar
             target.SecuritySchemes = new Dictionary<string, OpenApiSecurityScheme>(source.SecuritySchemes);
             target.SecurityRequirements = new List<OpenApiSecurityRequirement>(source.SecurityRequirements);
             target.ParameterFilters = new List<IParameterFilter>(source.ParameterFilters);
+            target.ParameterAsyncFilters = new List<IParameterAsyncFilter>(source.ParameterAsyncFilters);
             target.OperationFilters = new List<IOperationFilter>(source.OperationFilters);
+            target.OperationAsyncFilters = new List<IOperationAsyncFilter>(source.OperationAsyncFilters);
             target.DocumentFilters = new List<IDocumentFilter>(source.DocumentFilters);
+            target.DocumentAsyncFilters = new List<IDocumentAsyncFilter>(source.DocumentAsyncFilters);
             target.RequestBodyFilters = new List<IRequestBodyFilter>(source.RequestBodyFilters);
+            target.RequestBodyAsyncFilters = new List<IRequestBodyAsyncFilter>(source.RequestBodyAsyncFilters);
             target.SecuritySchemesSelector = source.SecuritySchemesSelector;
         }
 

src/Swashbuckle.AspNetCore.SwaggerGen/DependencyInjection/SwaggerGenServiceCollectionExtensions.cs

@@ -23,9 +23,10 @@ public static IServiceCollection AddSwaggerGen(
             services.AddTransient<IConfigureOptions<SwaggerGeneratorOptions>, ConfigureSwaggerGeneratorOptions>();
             services.AddTransient<IConfigureOptions<SchemaGeneratorOptions>, ConfigureSchemaGeneratorOptions>();
 
-            // Register generator and it's dependencies
-            services.TryAddTransient<ISwaggerProvider, SwaggerGenerator>();
-            services.TryAddTransient<IAsyncSwaggerProvider, SwaggerGenerator>();
+            // Register generator and its dependencies
+            services.TryAddTransient<SwaggerGenerator>();
+            services.TryAddTransient<ISwaggerProvider>(s => s.GetRequiredService<SwaggerGenerator>());
+            services.TryAddTransient<IAsyncSwaggerProvider>(s => s.GetRequiredService<SwaggerGenerator>());
             services.TryAddTransient(s => s.GetRequiredService<IOptions<SwaggerGeneratorOptions>>().Value);
             services.TryAddTransient<ISchemaGenerator, SchemaGenerator>();
             services.TryAddTransient(s => s.GetRequiredService<IOptions<SchemaGeneratorOptions>>().Value);
@@ -53,13 +54,15 @@ public static void ConfigureSwaggerGen(
 
         private sealed class JsonSerializerOptionsProvider
         {
-            private readonly IServiceProvider _serviceProvider;
             private JsonSerializerOptions _options;
+#if !NETSTANDARD2_0
+            private readonly IServiceProvider _serviceProvider;
 
             public JsonSerializerOptionsProvider(IServiceProvider serviceProvider)
             {
                 _serviceProvider = serviceProvider;
             }
+#endif
 
             public JsonSerializerOptions Options => _options ??= ResolveOptions();
 

src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/IDocumentFilter.cs

@@ -1,4 +1,6 @@
 using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.ApiExplorer;
 using Microsoft.OpenApi.Models;
 
@@ -9,6 +11,11 @@ public interface IDocumentFilter
         void Apply(OpenApiDocument swaggerDoc, DocumentFilterContext context);
     }
 
+    public interface IDocumentAsyncFilter
+    {
+        Task ApplyAsync(OpenApiDocument swaggerDoc, DocumentFilterContext context, CancellationToken cancellationToken);
+    }
+
     public class DocumentFilterContext
     {
         public DocumentFilterContext(

src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/IOperationFilter.cs

@@ -1,4 +1,6 @@
 using System.Reflection;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.ApiExplorer;
 using Microsoft.OpenApi.Models;
 
@@ -9,6 +11,11 @@ public interface IOperationFilter
         void Apply(OpenApiOperation operation, OperationFilterContext context);
     }
 
+    public interface IOperationAsyncFilter
+    {
+        Task ApplyAsync(OpenApiOperation operation, OperationFilterContext context, CancellationToken cancellationToken);
+    }
+
     public class OperationFilterContext
     {
         public OperationFilterContext(

src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/IParameterFilter.cs

@@ -1,4 +1,6 @@
 using System.Reflection;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.ApiExplorer;
 using Microsoft.OpenApi.Models;
 
@@ -9,6 +11,11 @@ public interface IParameterFilter
         void Apply(OpenApiParameter parameter, ParameterFilterContext context);
     }
 
+    public interface IParameterAsyncFilter
+    {
+        Task ApplyAsync(OpenApiParameter parameter, ParameterFilterContext context, CancellationToken cancellationToken);
+    }
+
     public class ParameterFilterContext
     {
         public ParameterFilterContext(

src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/IRequestBodyFilter.cs

@@ -1,4 +1,6 @@
 using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.ApiExplorer;
 using Microsoft.OpenApi.Models;
 
@@ -9,6 +11,11 @@ public interface IRequestBodyFilter
         void Apply(OpenApiRequestBody requestBody, RequestBodyFilterContext context);
     }
 
+    public interface IRequestBodyAsyncFilter
+    {
+        Task ApplyAsync(OpenApiRequestBody requestBody, RequestBodyFilterContext context, CancellationToken cancellationToken);
+    }
+
     public class RequestBodyFilterContext
     {
         public RequestBodyFilterContext(