Fixes #1661 - Make IDocumentFilter async compatible

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

@@ -46,6 +46,9 @@ public void Configure(SwaggerGeneratorOptions options)
             _swaggerGenOptions.DocumentFilterDescriptors.ForEach(
                 filterDescriptor => options.DocumentFilters.Add(CreateFilter<IDocumentFilter>(filterDescriptor)));
 
+            _swaggerGenOptions.DocumentAsyncFilterDescriptors.ForEach(
+                filterDescriptor => options.DocumentAsyncFilters.Add(CreateFilter<IDocumentAsyncFilter>(filterDescriptor)));
+
             if (!options.SwaggerDocs.Any())
             {
                 options.SwaggerDocs.Add("v1", new OpenApiInfo { Title = _hostingEnv.ApplicationName, Version = "1.0" });
@@ -69,6 +72,7 @@ public void DeepCopy(SwaggerGeneratorOptions source, SwaggerGeneratorOptions tar
             target.ParameterFilters = new List<IParameterFilter>(source.ParameterFilters);
             target.OperationFilters = new List<IOperationFilter>(source.OperationFilters);
             target.DocumentFilters = new List<IDocumentFilter>(source.DocumentFilters);
+            target.DocumentAsyncFilters = new List<IDocumentAsyncFilter>(source.DocumentAsyncFilters);
         }
 
         private TFilter CreateFilter<TFilter>(FilterDescriptor filterDescriptor)

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

@@ -22,6 +22,8 @@ public class SwaggerGenOptions
 
         public List<FilterDescriptor> DocumentFilterDescriptors { get; set; } = new List<FilterDescriptor>();
 
+        public List<FilterDescriptor> DocumentAsyncFilterDescriptors { get; set; } = new List<FilterDescriptor>();
+
         public List<FilterDescriptor> SchemaFilterDescriptors { get; set; } = new List<FilterDescriptor>();
     }
 

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

@@ -415,6 +415,24 @@ public static void SupportNonNullableReferenceTypes(this SwaggerGenOptions swagg
             });
         }
 
+        /// <summary>
+        /// Extend the Swagger Generator with async "filters" that can modify SwaggerDocuments after they're initially generated
+        /// </summary>
+        /// <typeparam name="TFilter">A type that derives from IDocumentAsyncFilter</typeparam>
+        /// <param name="swaggerGenOptions"></param>
+        /// <param name="arguments">Optionally inject parameters through filter constructors</param>
+        public static void DocumentAsyncFilter<TFilter>(
+            this SwaggerGenOptions swaggerGenOptions,
+            params object[] arguments)
+            where TFilter : IDocumentAsyncFilter
+        {
+            swaggerGenOptions.DocumentFilterDescriptors.Add(new FilterDescriptor
+            {
+                Type = typeof(TFilter),
+                Arguments = arguments
+            });
+        }
+
         /// <summary>
         /// Inject human-friendly descriptions for Operations, Parameters and Schemas based on XML Comment files
         /// </summary>

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

@@ -1,14 +1,22 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.ApiExplorer;
 using Microsoft.OpenApi.Models;
 
 namespace Swashbuckle.AspNetCore.SwaggerGen
 {
+
     public interface IDocumentFilter
     {
         void Apply(OpenApiDocument swaggerDoc, DocumentFilterContext context);
     }
 
+    public interface IDocumentAsyncFilter
+    {
+        Task Apply(OpenApiDocument swaggerDoc, DocumentFilterContext context);
+    }
+
     public class DocumentFilterContext
     {
         public DocumentFilterContext(

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

@@ -52,6 +52,11 @@ public async Task<OpenApiDocument> GetSwaggerAsync(string documentName, string h
                 filter.Apply(swaggerDoc, filterContext);
             }
 
+            foreach (var filter in _options.DocumentAsyncFilters)
+            {
+                await filter.Apply(swaggerDoc, filterContext);
+            }
+
             swaggerDoc.Components.Schemas = new SortedDictionary<string, OpenApiSchema>(swaggerDoc.Components.Schemas, _options.SchemaComparer);
 
             return swaggerDoc;
@@ -70,8 +75,15 @@ public OpenApiDocument GetSwagger(string documentName, string host = null, strin
                 filter.Apply(swaggerDoc, filterContext);
             }
 
-            swaggerDoc.Components.Schemas = new SortedDictionary<string, OpenApiSchema>(swaggerDoc.Components.Schemas, _options.SchemaComparer);
+            if (_options.DocumentAsyncFilters?.Any() ?? false)
+            {
+                throw new SwaggerGeneratorException("DocumentAsyncFilters are configured but not using GetSwaggerAsync(). " +
+                        "Use GetSwaggerAsync() instead of GetSwagger()");
+            }
 
+
+            swaggerDoc.Components.Schemas = new SortedDictionary<string, OpenApiSchema>(swaggerDoc.Components.Schemas, _options.SchemaComparer);
+
             return swaggerDoc;
         }
 

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

@@ -29,6 +29,7 @@ public SwaggerGeneratorOptions()
             RequestBodyFilters = new List<IRequestBodyFilter>();
             OperationFilters = new List<IOperationFilter>();
             DocumentFilters = new List<IDocumentFilter>();
+            DocumentAsyncFilters = new List<IDocumentAsyncFilter>();
         }
 
         public IDictionary<string, OpenApiInfo> SwaggerDocs { get; set; }
@@ -67,6 +68,9 @@ public SwaggerGeneratorOptions()
 
         public IList<IDocumentFilter> DocumentFilters { get; set; }
 
+        public IList<IDocumentAsyncFilter> DocumentAsyncFilters { get; set; }
+
+
         private bool DefaultDocInclusionPredicate(string documentName, ApiDescription apiDescription)
         {
             return apiDescription.GroupName == null || apiDescription.GroupName == documentName;

test/Swashbuckle.AspNetCore.SwaggerGen.Test/Fixtures/TestDocumentAsyncFilter.cs

@@ -0,0 +1,19 @@
+using Microsoft.OpenApi.Any;
+using Microsoft.OpenApi.Models;
+using Swashbuckle.AspNetCore.TestSupport;
+using System.Threading.Tasks;
+
+namespace Swashbuckle.AspNetCore.SwaggerGen.Test
+{
+    public class TestDocumentAsyncFilter : IDocumentAsyncFilter
+    {
+        public Task Apply(OpenApiDocument swaggerDoc, DocumentFilterContext context)
+        {
+            swaggerDoc.Extensions.Add("X-foo", new OpenApiString("bar"));
+            swaggerDoc.Extensions.Add("X-docName", new OpenApiString(context.DocumentName));
+            context.SchemaGenerator.GenerateSchema(typeof(ComplexType), context.SchemaRepository);
+
+            return Task.CompletedTask;
+        }
+    }
+}

test/Swashbuckle.AspNetCore.SwaggerGen.Test/SwaggerGenerator/SwaggerGeneratorTests.cs

@@ -1277,6 +1277,32 @@ public void GetSwagger_SupportsOption_DocumentFilters()
             Assert.Contains("ComplexType", document.Components.Schemas.Keys);
         }
 
+        [Fact]
+        public async Task GetSwagger_SupportsOption_AsyncDocumentFilters()
+        {
+            var subject = Subject(
+                apiDescriptions: new ApiDescription[] { },
+                options: new SwaggerGeneratorOptions
+                {
+                    SwaggerDocs = new Dictionary<string, OpenApiInfo>
+                    {
+                        ["v1"] = new OpenApiInfo { Version = "V1", Title = "Test API" }
+                    },
+                    DocumentAsyncFilters = new List<IDocumentAsyncFilter>
+                    {
+                        new TestDocumentAsyncFilter()
+                    }
+                }
+            );
+
+            var document = await subject.GetSwaggerAsync("v1");
+
+            Assert.Equal(2, document.Extensions.Count);
+            Assert.Equal("bar", ((OpenApiString)document.Extensions["X-foo"]).Value);
+            Assert.Equal("v1", ((OpenApiString)document.Extensions["X-docName"]).Value);
+            Assert.Contains("ComplexType", document.Components.Schemas.Keys);
+        }
+
         private SwaggerGenerator Subject(
             IEnumerable<ApiDescription> apiDescriptions,
             SwaggerGeneratorOptions options = null,