Add support for binding record types

src/Mvc/Mvc.Abstractions/src/ModelBinding/Metadata/ModelBindingMessageProvider.cs

@@ -43,7 +43,7 @@ public abstract class ModelBindingMessageProvider
         /// <summary>
         /// Error message the model binding system adds when <see cref="ModelError.Exception"/> is of type
         /// <see cref="FormatException"/> or <see cref="OverflowException"/>, value is known, and error is associated
-        /// with a property or parameter.
+        /// with a property.
         /// </summary>
         /// <value>Default <see cref="string"/> is "The value '{0}' is not valid for {1}.".</value>
         public virtual Func<string, string, string> AttemptedValueIsInvalidAccessor { get; } = default!;

src/Mvc/Mvc.Abstractions/src/ModelBinding/ModelMetadata.cs

@@ -106,7 +106,7 @@ internal IReadOnlyList<ModelMetadata> BoundProperties
             get
             {
                 // In record types, each constructor parameter in the primary constructor is also a settable property with the same name.
-                // Executing model binding on these parameters twice may have detrimental effects, such as duplicate validation entries,
+                // Executing model binding on these parameters twice may have detrimental effects, such as duplicate ModelState entries,
                 // or failures if a model expects to be bound exactly ones.
                 // Consequently when binding to a constructor, we only bind and validate the subset of properties whose names
                 // haven't appeared as parameters.

src/Mvc/Mvc.Core/src/ModelBinding/Binders/ComplexObjectModelBinder.cs

@@ -36,7 +36,6 @@ public sealed class ComplexObjectModelBinder : IModelBinder
         private readonly ILogger _logger;
         private Func<object> _modelCreator;
 
-
         internal ComplexObjectModelBinder(
             IDictionary<ModelMetadata, IModelBinder> propertyBinders,
             IReadOnlyList<IModelBinder> parameterBinders,
@@ -83,7 +82,7 @@ private async Task BindModelCoreAsync(ModelBindingContext bindingContext, int pr
                 if (boundConstructor != null)
                 {
                     var values = new object[boundConstructor.BoundConstructorParameters.Count];
-                    var (attemptedParameterBinding, parameterBindingSucceeded) = await BindParameters(
+                    var (attemptedParameterBinding, parameterBindingSucceeded) = await BindParametersAsync(
                         bindingContext,
                         propertyData,
                         boundConstructor.BoundConstructorParameters,
@@ -103,7 +102,7 @@ private async Task BindModelCoreAsync(ModelBindingContext bindingContext, int pr
                 }
             }
 
-            var (attemptedPropertyBinding, propertyBindingSucceeded) = await BindProperties(
+            var (attemptedPropertyBinding, propertyBindingSucceeded) = await BindPropertiesAsync(
                 bindingContext,
                 propertyData,
                 modelMetadata.BoundProperties);
@@ -225,7 +224,7 @@ internal void CreateModel(ModelBindingContext bindingContext)
             bindingContext.Model = _modelCreator();
         }
 
-        private async ValueTask<(bool attemptedBinding, bool bindingSucceeded)> BindParameters(
+        private async ValueTask<(bool attemptedBinding, bool bindingSucceeded)> BindParametersAsync(
             ModelBindingContext bindingContext,
             int propertyData,
             IReadOnlyList<ModelMetadata> parameters,
@@ -322,7 +321,7 @@ internal void CreateModel(ModelBindingContext bindingContext)
             return (attemptedBinding, bindingSucceeded);
         }
 
-        private async ValueTask<(bool attemptedBinding, bool bindingSucceeded)> BindProperties(
+        private async ValueTask<(bool attemptedBinding, bool bindingSucceeded)> BindPropertiesAsync(
             ModelBindingContext bindingContext,
             int propertyData,
             IReadOnlyList<ModelMetadata> boundProperties)
@@ -344,9 +343,6 @@ internal void CreateModel(ModelBindingContext bindingContext)
                     continue;
                 }
 
-                var fieldName = property.BinderModelName ?? property.PropertyName;
-                var modelName = ModelNames.CreatePropertyModelName(bindingContext.ModelName, fieldName);
-
                 var propertyBinder = _propertyBinders[property];
                 if (propertyBinder is PlaceholderBinder)
                 {
@@ -372,6 +368,8 @@ internal void CreateModel(ModelBindingContext bindingContext)
                     }
                 }
 
+                var fieldName = property.BinderModelName ?? property.PropertyName;
+                var modelName = ModelNames.CreatePropertyModelName(bindingContext.ModelName, fieldName);
                 var result = await BindPropertyAsync(bindingContext, property, propertyBinder, fieldName, modelName);
 
                 if (result.IsModelSet)

src/Mvc/Mvc.Core/src/ModelBinding/Binders/ComplexObjectModelBinderProvider.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -25,6 +25,7 @@ public IModelBinder GetBinder(ModelBinderProviderContext context)
             if (metadata.IsComplexType && !metadata.IsCollectionType)
             {
                 var loggerFactory = context.Services.GetRequiredService<ILoggerFactory>();
+                var logger = loggerFactory.CreateLogger<ComplexObjectModelBinder>();
                 var parameterBinders = GetParameterBinders(context);
 
                 var propertyBinders = new Dictionary<ModelMetadata, IModelBinder>();
@@ -34,7 +35,7 @@ public IModelBinder GetBinder(ModelBinderProviderContext context)
                     propertyBinders.Add(property, context.CreateBinder(property));
                 }
 
-                return new ComplexObjectModelBinder(propertyBinders, parameterBinders, loggerFactory.CreateLogger<ComplexObjectModelBinder>());
+                return new ComplexObjectModelBinder(propertyBinders, parameterBinders, logger);
             }
 
             return null;
@@ -48,7 +49,9 @@ private static IReadOnlyList<IModelBinder> GetParameterBinders(ModelBinderProvid
                 return Array.Empty<IModelBinder>();
             }
 
-            var parameterBinders = boundConstructor.BoundConstructorParameters.Count == 0 ? Array.Empty<IModelBinder>() : new IModelBinder[boundConstructor.BoundConstructorParameters.Count];
+            var parameterBinders = boundConstructor.BoundConstructorParameters.Count == 0 ?
+                Array.Empty<IModelBinder>() :
+                new IModelBinder[boundConstructor.BoundConstructorParameters.Count];
 
             for (var i = 0; i < parameterBinders.Length; i++)
             {

src/Mvc/Mvc.Core/src/ModelBinding/Metadata/DefaultBindingMetadataProvider.cs

@@ -116,6 +116,12 @@ private static ConstructorInfo GetRecordTypeConstructor(Type type, ConstructorIn
             var constructor = constructors[0];
 
             var parameters = constructor.GetParameters();
+            if (parameters.Length == 0)
+            {
+                // We do not need to do special handling for parameterless constructors.
+                return null;
+            }
+
             var properties = PropertyHelper.GetVisibleProperties(type);
 
             for (var i = 0; i < parameters.Length; i++)

src/Mvc/Mvc.Core/src/ModelBinding/Metadata/DefaultModelMetadataProvider.cs

@@ -282,8 +282,7 @@ private DefaultMetadataDetails CreateConstructorDetails(ModelMetadataIdentity co
                 var args = Expression.Parameter(typeof(object[]), "args");
                 var factoryExpressionBody = BuildFactoryExpression(constructor, args);
 
-                var factoryLamda = Expression.Lambda<Func<object[], object>>(
-                   factoryExpressionBody, args);
+                var factoryLamda = Expression.Lambda<Func<object[], object>>(factoryExpressionBody, args);
 
                 return factoryLamda.Compile();
             }

src/Mvc/Mvc.Core/src/ModelBinding/ParameterBinder.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;

src/Mvc/Mvc.Core/src/Resources.resx

@@ -532,6 +532,6 @@
     <value>Could not create an instance of type '{0}'. Model bound complex types must not be abstract or value types and must have a parameterless constructor. Record types must have a single primary constructor.</value>
   </data>
   <data name="ValidationStrategy_MappedPropertyNotFound" xml:space="preserve">
-    <value>No property found that maps to constructor parameter '{0}' for type '{1}'. Validation requires that each bound parameter must have a property to read the value.</value>
+    <value>No property found that maps to pconstructor parameter '{0}' for type '{1}'. Validation requires that each bound parameter of a record type's primary constructor must have a property to read the value.</value>
   </data>
 </root>

src/Mvc/Mvc.Core/test/ModelBinding/Binders/ComplexObjectModelBinderProviderTest.cs

@@ -8,7 +8,6 @@
 
 namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
-    [Obsolete]
     public class ComplexObjectModelBinderProviderTest
     {
         [Theory]

src/Mvc/Mvc.Core/test/ModelBinding/Binders/ComplexTypeModelBinderTest.cs

@@ -19,7 +19,7 @@
 
 namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
 {
-    [Obsolete]
+#pragma warning disable CS0618 // Type or member is obsolete
     public class ComplexTypeModelBinderTest
     {
         private static readonly IModelMetadataProvider _metadataProvider = TestModelMetadataProvider.CreateDefaultProvider();
@@ -1662,4 +1662,5 @@ protected override object CreateModel(ModelBindingContext bindingContext)
             }
         }
     }
+#pragma warning restore CS0618 // Type or member is obsolete
 }

src/Mvc/Mvc.Core/test/ModelBinding/Metadata/DefaultBindingMetadataProviderTest.cs

@@ -748,17 +748,27 @@ public void GetBoundConstructor_ReturnsPrimaryConstructor_ForRecordType()
                 p => Assert.Equal("name", p.Name));
         }
 
-        private record RecordTypeWithPrimaryAndParameterlessConstructor(string name)
+        private record RecordTypeWithDefaultConstructor
         {
-            public RecordTypeWithPrimaryAndParameterlessConstructor() : this(string.Empty) {}
+            public string Name { get; init; }
+
+            public int Age { get; init; }
         }
 
-        [Fact]
-        public void GetBoundConstructor_ReturnsNull_ForRecordTypeWithParameterlessConstructor()
+        private record RecordTypeWithParameterlessConstructor
         {
-            // Arrange
-            var type = typeof(RecordTypeWithPrimaryAndParameterlessConstructor);
+            public RecordTypeWithParameterlessConstructor() { }
+
+            public string Name { get; init; }
 
+            public int Age { get; init; }
+        }
+
+        [Theory]
+        [InlineData(typeof(RecordTypeWithDefaultConstructor))]
+        [InlineData(typeof(RecordTypeWithParameterlessConstructor))]
+        public void GetBoundConstructor_ReturnsNull_ForRecordTypeWithParameterlessConstructor(Type type)
+        {
             // Act
             var result = DefaultBindingMetadataProvider.GetBoundConstructor(type);