#2765 Allow Filter instance reuse

Directory.Packages.props

@@ -13,6 +13,7 @@
     <PackageVersion Include="Microsoft.AspNetCore.Mvc.Testing" Version="6.0.28" />
     <PackageVersion Include="Microsoft.AspNetCore.Mvc.Versioning" Version="5.1.0" />
     <PackageVersion Include="Microsoft.AspNetCore.Mvc.Versioning.ApiExplorer" Version="5.1.0" />
+    <PackageVersion Include="Microsoft.AspNetCore.OpenApi" Version="8.0.4" />
     <PackageVersion Include="Microsoft.AspNetCore.Razor.Design" Version="2.1.2" />
     <PackageVersion Include="Microsoft.AspNetCore.Routing" Version="2.1.0" />
     <PackageVersion Include="Microsoft.AspNetCore.StaticFiles" Version="2.1.0" />
@@ -22,11 +23,12 @@
     <PackageVersion Include="Microsoft.OpenApi.Readers" Version="1.6.14" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageVersion Include="Newtonsoft.Json" Version="13.0.3" />
+    <PackageVersion Include="NSubstitute" Version="5.1.0" />
     <PackageVersion Include="Nswag.MSbuild" Version="13.17.0" />
     <PackageVersion Include="ReportGenerator" Version="5.2.2" />
     <PackageVersion Include="System.Text.Json" Version="4.6.0" />
     <PackageVersion Include="xunit" Version="2.7.0" />
     <PackageVersion Include="xunit.core" Version="2.7.0" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.7" />
   </ItemGroup>
-</Project>
+</Project>

Swashbuckle.AspNetCore.sln

@@ -1,4 +1,3 @@
-
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
 VisualStudioVersion = 17.0.31717.71

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

@@ -25,7 +25,7 @@ public void Configure(SchemaGeneratorOptions options)
 
             // Create and add any filters that were specified through the FilterDescriptor lists
             _swaggerGenOptions.SchemaFilterDescriptors.ForEach(
-                filterDescriptor => options.SchemaFilters.Add(CreateFilter<ISchemaFilter>(filterDescriptor)));
+                filterDescriptor => options.SchemaFilters.Add(GetOrCreateFilter<ISchemaFilter>(filterDescriptor)));
         }
 
         private void DeepCopy(SchemaGeneratorOptions source, SchemaGeneratorOptions target)
@@ -44,10 +44,10 @@ private void DeepCopy(SchemaGeneratorOptions source, SchemaGeneratorOptions targ
             target.SchemaFilters = new List<ISchemaFilter>(source.SchemaFilters);
         }
 
-        private TFilter CreateFilter<TFilter>(FilterDescriptor filterDescriptor)
+        private TFilter GetOrCreateFilter<TFilter>(FilterDescriptor filterDescriptor)
         {
-            return (TFilter)ActivatorUtilities
-                .CreateInstance(_serviceProvider, filterDescriptor.Type, filterDescriptor.Arguments);
+            return (TFilter)(filterDescriptor.FilterInstance
+                ?? ActivatorUtilities .CreateInstance(_serviceProvider, filterDescriptor.Type, filterDescriptor.Arguments));
         }
     }
-}
+}

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

@@ -35,16 +35,16 @@ public void Configure(SwaggerGeneratorOptions options)
             // Create and add any filters that were specified through the FilterDescriptor lists ...
 
             _swaggerGenOptions.ParameterFilterDescriptors.ForEach(
-                filterDescriptor => options.ParameterFilters.Add(CreateFilter<IParameterFilter>(filterDescriptor)));
+                filterDescriptor => options.ParameterFilters.Add(GetOrCreateFilter<IParameterFilter>(filterDescriptor)));
 
             _swaggerGenOptions.RequestBodyFilterDescriptors.ForEach(
-                filterDescriptor => options.RequestBodyFilters.Add(CreateFilter<IRequestBodyFilter>(filterDescriptor)));
+                filterDescriptor => options.RequestBodyFilters.Add(GetOrCreateFilter<IRequestBodyFilter>(filterDescriptor)));
 
             _swaggerGenOptions.OperationFilterDescriptors.ForEach(
-                filterDescriptor => options.OperationFilters.Add(CreateFilter<IOperationFilter>(filterDescriptor)));
+                filterDescriptor => options.OperationFilters.Add(GetOrCreateFilter<IOperationFilter>(filterDescriptor)));
 
             _swaggerGenOptions.DocumentFilterDescriptors.ForEach(
-                filterDescriptor => options.DocumentFilters.Add(CreateFilter<IDocumentFilter>(filterDescriptor)));
+                filterDescriptor => options.DocumentFilters.Add(GetOrCreateFilter<IDocumentFilter>(filterDescriptor)));
 
             if (!options.SwaggerDocs.Any())
             {
@@ -74,10 +74,10 @@ public void DeepCopy(SwaggerGeneratorOptions source, SwaggerGeneratorOptions tar
             target.SecuritySchemesSelector = source.SecuritySchemesSelector;
         }
 
-        private TFilter CreateFilter<TFilter>(FilterDescriptor filterDescriptor)
+        private TFilter GetOrCreateFilter<TFilter>(FilterDescriptor filterDescriptor)
         {
-            return (TFilter)ActivatorUtilities
-                .CreateInstance(_serviceProvider, filterDescriptor.Type, filterDescriptor.Arguments);
+            return (TFilter)(filterDescriptor.FilterInstance
+                ?? ActivatorUtilities.CreateInstance(_serviceProvider, filterDescriptor.Type, filterDescriptor.Arguments));
         }
     }
 }

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

@@ -30,5 +30,7 @@ public class FilterDescriptor
         public Type Type { get; set; }
 
         public object[] Arguments { get; set; }
+
+        public object FilterInstance { get; set; }
     }
 }

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

@@ -328,93 +328,193 @@ public static void SupportNonNullableReferenceTypes(this SwaggerGenOptions swagg
         /// <summary>
         /// Extend the Swagger Generator with "filters" that can modify Schemas after they're initially generated
         /// </summary>
-        /// <typeparam name="TFilter">A type that derives from ISchemaFilter</typeparam>
+        /// <typeparam name="TFilter">A type that derives from <see cref="ISchemaFilter"/></typeparam>
         /// <param name="swaggerGenOptions"></param>
         /// <param name="arguments">Optionally inject parameters through filter constructors</param>
         public static void SchemaFilter<TFilter>(
             this SwaggerGenOptions swaggerGenOptions,
             params object[] arguments)
             where TFilter : ISchemaFilter
         {
+            swaggerGenOptions = swaggerGenOptions ?? throw new ArgumentNullException(nameof(swaggerGenOptions));
             swaggerGenOptions.SchemaFilterDescriptors.Add(new FilterDescriptor
             {
                 Type = typeof(TFilter),
                 Arguments = arguments
             });
         }
 
+        /// <summary>
+        /// Extend the Swagger Generator with "filters" that can modify Schemas after they're initially generated
+        /// </summary>
+        /// <typeparam name="TFilter">A type that derives from <see cref="ISchemaFilter"/></typeparam>
+        /// <param name="swaggerGenOptions"></param>
+        /// <param name="filterInstance">An instance of the filter, to enable reuse.</param>
+        public static void AddSchemaFilterInstance<TFilter>(
+            this SwaggerGenOptions swaggerGenOptions,
+            TFilter filterInstance)
+            where TFilter : ISchemaFilter
+        {
+            swaggerGenOptions = swaggerGenOptions ?? throw new ArgumentNullException(nameof(swaggerGenOptions));
+            filterInstance = filterInstance ?? throw new ArgumentNullException(nameof(filterInstance));
+            swaggerGenOptions.SchemaFilterDescriptors.Add(new FilterDescriptor
+            {
+                FilterInstance = filterInstance
+            });
+        }
+
         /// <summary>
         /// Extend the Swagger Generator with "filters" that can modify Parameters after they're initially generated
         /// </summary>
-        /// <typeparam name="TFilter">A type that derives from IParameterFilter</typeparam>
+        /// <typeparam name="TFilter">A type that derives from <see cref="IParameterFilter"/></typeparam>
         /// <param name="swaggerGenOptions"></param>
         /// <param name="arguments">Optionally inject parameters through filter constructors</param>
         public static void ParameterFilter<TFilter>(
             this SwaggerGenOptions swaggerGenOptions,
             params object[] arguments)
             where TFilter : IParameterFilter
         {
+            swaggerGenOptions = swaggerGenOptions ?? throw new ArgumentNullException(nameof(swaggerGenOptions));
             swaggerGenOptions.ParameterFilterDescriptors.Add(new FilterDescriptor
             {
                 Type = typeof(TFilter),
                 Arguments = arguments
             });
         }
 
+        /// <summary>
+        /// Extend the Swagger Generator with "filters" that can modify Parameters after they're initially generated
+        /// </summary>
+        /// <typeparam name="TFilter">A type that derives from <see cref="IParameterFilter"/></typeparam>
+        /// <param name="swaggerGenOptions"></param>
+        /// <param name="filterInstance">An instance of the filter, to enable reuse.</param>
+        public static void AddParameterFilterInstance<TFilter>(
+            this SwaggerGenOptions swaggerGenOptions,
+            TFilter filterInstance)
+            where TFilter : IParameterFilter
+        {
+            swaggerGenOptions = swaggerGenOptions ?? throw new ArgumentNullException(nameof(swaggerGenOptions));
+            filterInstance = filterInstance ?? throw new ArgumentNullException(nameof(filterInstance));
+            swaggerGenOptions.ParameterFilterDescriptors.Add(new FilterDescriptor
+            {
+                FilterInstance = filterInstance
+            });
+        }
+
         /// <summary>
         /// Extend the Swagger Generator with "filters" that can modify RequestBodys after they're initially generated
         /// </summary>
-        /// <typeparam name="TFilter">A type that derives from IRequestBodyFilter</typeparam>
+        /// <typeparam name="TFilter">A type that derives from <see cref="IRequestBodyFilter"/></typeparam>
         /// <param name="swaggerGenOptions"></param>
         /// <param name="arguments">Optionally inject parameters through filter constructors</param>
         public static void RequestBodyFilter<TFilter>(
             this SwaggerGenOptions swaggerGenOptions,
             params object[] arguments)
             where TFilter : IRequestBodyFilter
         {
+            swaggerGenOptions = swaggerGenOptions ?? throw new ArgumentNullException(nameof(swaggerGenOptions));
             swaggerGenOptions.RequestBodyFilterDescriptors.Add(new FilterDescriptor
             {
                 Type = typeof(TFilter),
                 Arguments = arguments
             });
         }
 
+        /// <summary>
+        /// Extend the Swagger Generator with "filters" that can modify RequestBodys after they're initially generated
+        /// </summary>
+        /// <typeparam name="TFilter">A type that derives from <see cref="IRequestBodyFilter"/></typeparam>
+        /// <param name="swaggerGenOptions"></param>
+        /// <param name="filterInstance">An instance of the filter, to enable reuse.</param>
+        public static void AddRequestBodyFilterInstance<TFilter>(
+            this SwaggerGenOptions swaggerGenOptions,
+            TFilter filterInstance)
+            where TFilter : IRequestBodyFilter
+        {
+            swaggerGenOptions = swaggerGenOptions ?? throw new ArgumentNullException(nameof(swaggerGenOptions));
+            filterInstance = filterInstance ?? throw new ArgumentNullException(nameof(filterInstance));
+            swaggerGenOptions.RequestBodyFilterDescriptors.Add(new FilterDescriptor
+            {
+                FilterInstance = filterInstance
+            });
+        }
+
         /// <summary>
         /// Extend the Swagger Generator with "filters" that can modify Operations after they're initially generated
         /// </summary>
-        /// <typeparam name="TFilter">A type that derives from IOperationFilter</typeparam>
+        /// <typeparam name="TFilter">A type that derives from <see cref="IOperationFilter"/></typeparam>
         /// <param name="swaggerGenOptions"></param>
         /// <param name="arguments">Optionally inject parameters through filter constructors</param>
         public static void OperationFilter<TFilter>(
             this SwaggerGenOptions swaggerGenOptions,
             params object[] arguments)
             where TFilter : IOperationFilter
         {
+            swaggerGenOptions = swaggerGenOptions ?? throw new ArgumentNullException(nameof(swaggerGenOptions));
             swaggerGenOptions.OperationFilterDescriptors.Add(new FilterDescriptor
             {
                 Type = typeof(TFilter),
                 Arguments = arguments
             });
         }
 
+        /// <summary>
+        /// Extend the Swagger Generator with "filters" that can modify Operations after they're initially generated
+        /// </summary>
+        /// <typeparam name="TFilter">A type that derives from <see cref="IOperationFilter"/></typeparam>
+        /// <param name="swaggerGenOptions"></param>
+        /// <param name="filterInstance">An instance of the filter, to enable reuse.</param>
+        public static void AddOperationFilterInstance<TFilter>(
+            this SwaggerGenOptions swaggerGenOptions,
+            TFilter filterInstance)
+            where TFilter : IOperationFilter
+        {
+            swaggerGenOptions = swaggerGenOptions ?? throw new ArgumentNullException(nameof(swaggerGenOptions));
+            filterInstance = filterInstance ?? throw new ArgumentNullException(nameof(filterInstance));
+            swaggerGenOptions.OperationFilterDescriptors.Add(new FilterDescriptor
+            {
+                FilterInstance = filterInstance
+            });
+        }
+
         /// <summary>
         /// Extend the Swagger Generator with "filters" that can modify SwaggerDocuments after they're initially generated
         /// </summary>
-        /// <typeparam name="TFilter">A type that derives from IDocumentFilter</typeparam>
+        /// <typeparam name="TFilter">A type that derives from <see cref="IDocumentFilter"/></typeparam>
         /// <param name="swaggerGenOptions"></param>
         /// <param name="arguments">Optionally inject parameters through filter constructors</param>
         public static void DocumentFilter<TFilter>(
             this SwaggerGenOptions swaggerGenOptions,
             params object[] arguments)
             where TFilter : IDocumentFilter
         {
+            swaggerGenOptions = swaggerGenOptions ?? throw new ArgumentNullException(nameof(swaggerGenOptions));
             swaggerGenOptions.DocumentFilterDescriptors.Add(new FilterDescriptor
             {
                 Type = typeof(TFilter),
                 Arguments = arguments
             });
         }
 
+        /// <summary>
+        /// Extend the Swagger Generator with "filters" that can modify SwaggerDocuments after they're initially generated
+        /// </summary>
+        /// <typeparam name="TFilter">A type that derives from <see cref="IDocumentFilter"/></typeparam>
+        /// <param name="swaggerGenOptions"></param>
+        /// <param name="filterInstance">An instance of the filter, to enable reuse.</param>
+        public static void AddDocumentFilterInstance<TFilter>(
+            this SwaggerGenOptions swaggerGenOptions,
+            TFilter filterInstance)
+            where TFilter : IDocumentFilter
+        {
+            swaggerGenOptions = swaggerGenOptions ?? throw new ArgumentNullException(nameof(swaggerGenOptions));
+            filterInstance = filterInstance ?? throw new ArgumentNullException(nameof(filterInstance));
+            swaggerGenOptions.DocumentFilterDescriptors.Add(new FilterDescriptor
+            {
+                FilterInstance = filterInstance
+            });
+        }
+
         /// <summary>
         /// Inject human-friendly descriptions for Operations, Parameters and Schemas based on XML Comment files
         /// </summary>

src/Swashbuckle.AspNetCore.SwaggerGen/Properties/AssemblyInfo.cs

@@ -1,3 +1,4 @@
 using System.Runtime.CompilerServices;
 
 [assembly: InternalsVisibleTo("Swashbuckle.AspNetCore.IntegrationTests, PublicKey=0024000004800000940000000602000000240000525341310004000001000100795482b2b019ad690196ad34ca1d13abb1c3ed0e24fdaea1ca82ca11462a2d883e149864773aada8b40f41c1b1ea7824f23fb569cfc20e9fd03763896a2905fa23e1a62a940d40d14e3107e8cf90f6d705848e39fe25121a7f8c1cd5dcd6701aea982d13c4a42b3a0766dfc27fc02fa40194ed0a7841a8768d33f7aaabde87a7")]
+[assembly: InternalsVisibleTo("Swashbuckle.AspNetCore.SwaggerGen.Test, PublicKey=002400000480000094000000060200000024000052534131000400000100010055d6060294c6e19033fac1eb2d1a17f29d7ddd3a09b31f460302a2a7a9955cd1afaa6bd579125ee2ccce330e4dc84f238ed10d372a5c7db774ab2bf2dd77bf9fc0abb3fc84a32f0aacf4cf166c5af981e80419f83c0e4bb9868c3b9dd3a3c7e0a022b7da66ebfed28c073e99e3847491a84678ac55bcff5a2f573838518f4fef")]

test/Swashbuckle.AspNetCore.SwaggerGen.Test/ConfigureSwaggerGeneratorOptionsTests.cs

@@ -1,4 +1,10 @@
-using System.Reflection;
+using System.Linq;
+using System.Reflection;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting.Internal;
+using Microsoft.Extensions.Options;
+using NSubstitute;
 using Xunit;
 
 namespace Swashbuckle.AspNetCore.SwaggerGen.Test;
@@ -15,4 +21,27 @@ public static void DeepCopy_Copies_All_Properties()
         // to SwaggerGeneratorOptions and ConfigureSwaggerGeneratorOptions.DeepCopy() needs to be updated
         Assert.Equal(18, publicProperties.Length);
     }
+
+    [Fact]
+    public static void AddingDocumentFilterInstance_WhenConfiguringOption_SameInstanceIsAdded()
+    {
+        var webhostingEnvironment = Substitute.For<IWebHostEnvironment>();
+        webhostingEnvironment.ApplicationName.Returns("Swashbuckle.AspNetCore.SwaggerGen.Test");
+
+        var testDocumentFilter = new TestDocumentFilter();
+
+        var options = new SwaggerGenOptions();
+        options.AddDocumentFilterInstance(testDocumentFilter);
+
+        var configureSwaggerGeneratorOptions = new ConfigureSwaggerGeneratorOptions(
+            Options.Create(options),
+            null,
+            webhostingEnvironment);
+        var swaggerGeneratorOptions = new SwaggerGeneratorOptions();
+
+        configureSwaggerGeneratorOptions.Configure(swaggerGeneratorOptions);
+
+        Assert.Single(swaggerGeneratorOptions.DocumentFilters);
+        Assert.Same(testDocumentFilter, swaggerGeneratorOptions.DocumentFilters.First());
+    }
 }

test/Swashbuckle.AspNetCore.SwaggerGen.Test/Swashbuckle.AspNetCore.SwaggerGen.Test.csproj

@@ -4,6 +4,8 @@
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <NoWarn>1701;1702;1591</NoWarn>
     <TargetFrameworks>net6.0;net7.0</TargetFrameworks>
+    <SignAssembly>True</SignAssembly>
+    <AssemblyOriginatorKeyFile>Swashbuckle.AspNetCore.SwaggerGen.Test.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
 
   <ItemGroup>
@@ -14,6 +16,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="NSubstitute" />
     <PackageReference Include="xunit" />
     <PackageReference Include="xunit.runner.visualstudio" />
   </ItemGroup>