Infer BindingSource.FormFile for IEnumerable<IFormFile>

Fixes #7770

Author: pranavkm

src/Microsoft.AspNetCore.Mvc.Core/Internal/MvcCoreMvcOptionsSetup.cs

@@ -96,6 +96,7 @@ internal static void ConfigureAdditionalModelMetadataDetailsProviders(IList<IMet
             modelMetadataDetailsProviders.Add(new BindingSourceMetadataProvider(typeof(IFormFile), BindingSource.FormFile));
             modelMetadataDetailsProviders.Add(new BindingSourceMetadataProvider(typeof(IFormCollection), BindingSource.FormFile));
             modelMetadataDetailsProviders.Add(new BindingSourceMetadataProvider(typeof(IFormFileCollection), BindingSource.FormFile));
+            modelMetadataDetailsProviders.Add(new BindingSourceMetadataProvider(typeof(IEnumerable<IFormFile>), BindingSource.FormFile));
 
             // Add types to be excluded from Validation
             modelMetadataDetailsProviders.Add(new SuppressChildValidationMetadataProvider(typeof(Type)));

test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/DefaultApplicationModelProviderTest.cs

@@ -211,6 +211,52 @@ public void OnProvidersExecuting_AddsBindingSources_ForActionParameters_WithLega
                 });
         }
 
+        [Fact]
+        public void OnProvidersExecuting_InfersFormFileSourceForTypesAssignableFromIEnumerableOfFormFiles()
+        {
+            // Arrange
+            var builder = new TestApplicationModelProvider(
+                new MvcOptions { AllowValidatingTopLevelNodes = true },
+                TestModelMetadataProvider.CreateDefaultProvider());
+            var typeInfo = typeof(ModelBinderController).GetTypeInfo();
+
+            var context = new ApplicationModelProviderContext(new[] { typeInfo });
+
+            // Act
+            builder.OnProvidersExecuting(context);
+
+            // Assert
+            var controllerModel = Assert.Single(context.Result.Controllers);
+            var action = Assert.Single(controllerModel.Actions, a => a.ActionMethod.Name == nameof(ModelBinderController.FormFilesSequences));
+            Assert.Collection(
+                action.Parameters,
+                parameter =>
+                {
+                    Assert.Equal("formFileEnumerable", parameter.ParameterName);
+                    Assert.Equal(BindingSource.FormFile, parameter.BindingInfo.BindingSource);
+                },
+                parameter =>
+                {
+                    Assert.Equal("formFileCollection", parameter.ParameterName);
+                    Assert.Equal(BindingSource.FormFile, parameter.BindingInfo.BindingSource);
+                },
+                parameter =>
+                {
+                    Assert.Equal("formFileIList", parameter.ParameterName);
+                    Assert.Equal(BindingSource.FormFile, parameter.BindingInfo.BindingSource);
+                },
+                parameter =>
+                {
+                    Assert.Equal("formFileList", parameter.ParameterName);
+                    Assert.Equal(BindingSource.FormFile, parameter.BindingInfo.BindingSource);
+                },
+                parameter =>
+                {
+                    Assert.Equal("formFileArray", parameter.ParameterName);
+                    Assert.Equal(BindingSource.FormFile, parameter.BindingInfo.BindingSource);
+                });
+        }
+
         [Fact]
         public void OnProvidersExecuting_AddsBindingSources_ForActionParameters_ReadFromModelMetadata()
         {
@@ -1625,6 +1671,13 @@ public class ModelBinderController
 
             public IActionResult PostAction([FromQuery] string fromQuery, IFormFileCollection formFileCollection, string unbound) => null;
 
+            public IActionResult FormFilesSequences(
+                IEnumerable<IFormFile> formFileEnumerable,
+                ICollection<IFormFile> formFileCollection,
+                IList<IFormFile> formFileIList,
+                List<IFormFile> formFileList,
+                IFormFile[] formFileArray) => null;
+
             public IActionResult PostAction1(Guid guid) => null;
 
             public IActionResult PostAction2([FromQuery] Guid fromQuery) => null;

test/Microsoft.AspNetCore.Mvc.Test/MvcOptionsSetupTest.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
@@ -189,6 +190,12 @@ public void Setup_SetsUpMetadataDetailsProviders()
                     Assert.Equal(BindingSource.FormFile, formFileParameter.BindingSource);
                 },
                 provider =>
+                {
+                    var formFileParameter = Assert.IsType<BindingSourceMetadataProvider>(provider);
+                    Assert.Equal(typeof(IEnumerable<IFormFile>), formFileParameter.Type);
+                    Assert.Equal(BindingSource.FormFile, formFileParameter.BindingSource);
+                },
+                provider =>
                 {
                     var excludeFilter = Assert.IsType<SuppressChildValidationMetadataProvider>(provider);
                     Assert.Equal(typeof(Type), excludeFilter.Type);