Throw an error when a user uses FromForm attribute with IFormFile in …

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

@@ -5,12 +5,14 @@
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.ApiExplorer;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.OpenApi.Models;
 using Swashbuckle.AspNetCore.Annotations;
 using Swashbuckle.AspNetCore.Swagger;
+
 #if NET7_0_OR_GREATER
 using Microsoft.AspNetCore.Http.Metadata;
 #endif
@@ -328,6 +330,12 @@ private IList<OpenApiTag> GenerateOperationTags(ApiDescription apiDescription)
 
         private IList<OpenApiParameter> GenerateParameters(ApiDescription apiDescription, SchemaRepository schemaRespository)
         {
+            if (apiDescription.ParameterDescriptions.Any(apiParam => IsFromFormAttributeUsedWithIFormFile(apiParam)))
+                throw new SwaggerGeneratorException(string.Format(
+                       "Error reading parameter(s) for action {0} as [FromForm] attribute used with IFormFile. " +
+                       "Please refer to https://github.com/domaindrivendev/Swashbuckle.AspNetCore#handle-forms-and-file-uploads for more information",
+                       apiDescription.ActionDescriptor.DisplayName));
+
             var applicableApiParameters = apiDescription.ParameterDescriptions
                 .Where(apiParam =>
                 {
@@ -626,6 +634,17 @@ private OpenApiMediaType CreateResponseMediaType(ModelMetadata modelMetadata, Sc
             };
         }
 
+        private static bool IsFromFormAttributeUsedWithIFormFile(ApiParameterDescription apiParameter)
+        {
+            // Retrieve parameter information
+            var parameterInfo = apiParameter.ParameterInfo();
+
+            // Check if Parameter has FromForm Attribute
+            var fromFormAttribute = parameterInfo?.GetCustomAttribute<FromFormAttribute>();
+
+            return fromFormAttribute != null && parameterInfo?.ParameterType == typeof(IFormFile);
+        }
+
         private static readonly Dictionary<string, OperationType> OperationTypeMap = new Dictionary<string, OperationType>
         {
             { "GET", OperationType.Get },

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

@@ -1,6 +1,7 @@
 using System;
 using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
+using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Swashbuckle.AspNetCore.Annotations;
@@ -84,5 +85,11 @@ public int ActionWithProducesAttribute()
         [SwaggerIgnore]
         public void ActionWithSwaggerIgnoreAttribute()
         { }
+
+        public void ActionHavingIFormFileParamWithFromFormAtribute([FromForm] IFormFile fileUpload)
+        { }
+
+        public void ActionHavingFromFormAtributeButNotWithIFormFile([FromForm] string param1, IFormFile param2)
+        { }
     }
 }

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

@@ -7,6 +7,7 @@
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc.Abstractions;
 using Microsoft.AspNetCore.Mvc.ApiExplorer;
+using Microsoft.AspNetCore.Mvc.Controllers;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.OpenApi.Any;
@@ -1433,6 +1434,87 @@ public void GetSwagger_GeneratesSwaggerDocument_ThrowsIfHttpMethodNotSupported(s
             Assert.Equal($"The \"{httpMethod}\" HTTP method is not supported.", exception.Message);
         }
 
+        [Fact]
+        public void GetSwagger_Throws_Exception_When_FromForm_Attribute_Used_With_IFormFile()
+        {
+            var parameterInfo = typeof(FakeController)
+                .GetMethod(nameof(FakeController.ActionHavingIFormFileParamWithFromFormAtribute))
+                .GetParameters()[0];
+
+
+            var subject = Subject(
+                apiDescriptions: new[]
+                {
+                   ApiDescriptionFactory.Create<FakeController>(
+                        c => nameof(c.ActionHavingIFormFileParamWithFromFormAtribute),
+                        groupName: "v1",
+                        httpMethod: "POST",
+                        relativePath: "resource",
+                        parameterDescriptions: new[]
+                        {
+                            new ApiParameterDescription
+                            {
+                                Name = "fileUpload", // Name of the parameter
+                                Type = typeof(IFormFile), // Type of the parameter
+                                ParameterDescriptor = new ControllerParameterDescriptor { ParameterInfo = parameterInfo }
+                            }
+                        })
+                }
+            );
+
+            var exception = Assert.Throws<SwaggerGeneratorException>(() => subject.GetSwagger("v1"));
+        }
+
+        [Fact]
+        public void GetSwagger_Works_As_Expected_When_FromForm_Attribute_Not_Used_With_IFormFile()
+        {
+            var paraminfo = typeof(FakeController)
+                .GetMethod(nameof(FakeController.ActionHavingFromFormAtributeButNotWithIFormFile))
+                .GetParameters()[0];
+
+            var fileUploadParameterInfo = typeof(FakeController)
+                .GetMethod(nameof(FakeController.ActionHavingFromFormAtributeButNotWithIFormFile))
+                .GetParameters()[1];
+
+            var subject = Subject(
+                apiDescriptions: new[]
+                {
+                   ApiDescriptionFactory.Create<FakeController>(
+                        c => nameof(c.ActionHavingFromFormAtributeButNotWithIFormFile),
+                        groupName: "v1",
+                        httpMethod: "POST",
+                        relativePath: "resource",
+                        parameterDescriptions: new[]
+                        {
+                            new ApiParameterDescription
+                            {
+                                Name = "param1", // Name of the parameter
+                                Type = typeof(string), // Type of the parameter
+                                ParameterDescriptor = new ControllerParameterDescriptor { ParameterInfo = paraminfo }
+                            },
+                            new ApiParameterDescription
+                            {
+                                Name = "param2", // Name of the parameter
+                                Type = typeof(IFormFile), // Type of the parameter
+                                ParameterDescriptor = new ControllerParameterDescriptor { ParameterInfo = fileUploadParameterInfo }
+                            }
+                        })
+                }
+            );
+
+            var document = subject.GetSwagger("v1");
+
+            Assert.Equal("V1", document.Info.Version);
+            Assert.Equal("Test API", document.Info.Title);
+            Assert.Equal(new[] { "/resource" }, document.Paths.Keys.ToArray());
+
+            var operation = document.Paths["/resource"].Operations[OperationType.Post];
+            Assert.NotNull(operation.Parameters);
+            Assert.Equal(2, operation.Parameters.Count);
+            Assert.Equal("param1", operation.Parameters[0].Name);
+            Assert.Equal("param2", operation.Parameters[1].Name);
+        }
+
         private static SwaggerGenerator Subject(
             IEnumerable<ApiDescription> apiDescriptions,
             SwaggerGeneratorOptions options = null,