[Blazor] Initial support for [SupplyParameterFromForm]

src/Components/Authorization/test/AuthorizeRouteViewTest.cs

@@ -1,8 +1,10 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Diagnostics.CodeAnalysis;
 using System.Security.Claims;
 using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Components.Binding;
 using Microsoft.AspNetCore.Components.Rendering;
 using Microsoft.AspNetCore.Components.RenderTree;
 using Microsoft.AspNetCore.Components.Test.Helpers;
@@ -32,6 +34,7 @@ public AuthorizeRouteViewTest()
         serviceCollection.AddSingleton<IAuthorizationPolicyProvider, TestAuthorizationPolicyProvider>();
         serviceCollection.AddSingleton<IAuthorizationService>(_testAuthorizationService);
         serviceCollection.AddSingleton<NavigationManager, TestNavigationManager>();
+        serviceCollection.AddSingleton<IFormValueSupplier, TestFormValueSupplier>();
 
         var services = serviceCollection.BuildServiceProvider();
         _renderer = new TestRenderer(services);
@@ -467,4 +470,18 @@ public TestNavigationManager()
             Initialize("https://localhost:85/subdir/", "https://localhost:85/subdir/path?query=value#hash");
         }
     }
+
+    private class TestFormValueSupplier : IFormValueSupplier
+    {
+        public bool CanBind(string formName, Type valueType)
+        {
+            return false;
+        }
+
+        public bool TryBind(string formName, Type valueType, [NotNullWhen(true)] out object boundValue)
+        {
+            boundValue = null;
+            return false;
+        }
+    }
 }

src/Components/Components/src/Binding/CascadingModelBinder.cs

@@ -2,18 +2,21 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Reflection.Metadata;
+using Microsoft.AspNetCore.Components.Binding;
+using Microsoft.AspNetCore.Components.Rendering;
 using Microsoft.AspNetCore.Components.Routing;
 
 namespace Microsoft.AspNetCore.Components;
 
 /// <summary>
 /// Defines the binding context for data bound from external sources.
 /// </summary>
-public sealed class CascadingModelBinder : IComponent, IDisposable
+public sealed class CascadingModelBinder : IComponent, ICascadingValueComponent, IDisposable
 {
     private RenderHandle _handle;
     private ModelBindingContext? _bindingContext;
     private bool _hasPendingQueuedRender;
+    private BindingInfo? _bindingInfo;
 
     /// <summary>
     /// The binding context name.
@@ -35,7 +38,9 @@ public sealed class CascadingModelBinder : IComponent, IDisposable
 
     [CascadingParameter] ModelBindingContext? ParentContext { get; set; }
 
-    [Inject] private NavigationManager Navigation { get; set; } = null!;
+    [Inject] internal NavigationManager Navigation { get; set; } = null!;
+
+    [Inject] internal IFormValueSupplier FormValueSupplier { get; set; } = null!;
 
     void IComponent.Attach(RenderHandle renderHandle)
     {
@@ -87,7 +92,7 @@ private void HandleLocationChanged(object? sender, LocationChangedEventArgs e)
         Render();
     }
 
-    private void UpdateBindingInformation(string url)
+    internal void UpdateBindingInformation(string url)
     {
         // BindingContextId: action parameter used to define the handler
         // Name: form name and context used to bind
@@ -103,11 +108,11 @@ private void UpdateBindingInformation(string url)
         // 3) Parent has a name "parent-name"
         // Name = "parent-name.my-handler";
         // BindingContextId = <<base-relative-uri>>((<<existing-query>>&)|?)handler=my-handler
-        var name = string.IsNullOrEmpty(ParentContext?.Name) ? Name : $"{ParentContext.Name}.{Name}";
+        var name = ModelBindingContext.Combine(ParentContext, Name);
         var bindingId = string.IsNullOrEmpty(name) ? "" : GenerateBindingContextId(name);
 
         var bindingContext = _bindingContext != null &&
-            string.Equals(_bindingContext.Name, Name, StringComparison.Ordinal) &&
+            string.Equals(_bindingContext.Name, name, StringComparison.Ordinal) &&
             string.Equals(_bindingContext.BindingContextId, bindingId, StringComparison.Ordinal) ?
             _bindingContext : new ModelBindingContext(name, bindingId);
 
@@ -136,4 +141,54 @@ void IDisposable.Dispose()
     {
         Navigation.LocationChanged -= HandleLocationChanged;
     }
+
+    bool ICascadingValueComponent.CanSupplyValue(Type valueType, string? valueName)
+    {
+        var formName = string.IsNullOrEmpty(valueName) ?
+            (_bindingContext?.Name) :
+            ModelBindingContext.Combine(_bindingContext, valueName);
+
+        if (_bindingInfo != null &&
+            string.Equals(_bindingInfo.FormName, formName, StringComparison.Ordinal) &&
+            _bindingInfo.ValueType.Equals(valueType))
+        {
+            // We already bound the value, but some component might have been destroyed and
+            // re-created. If the type and name of the value that we bound are the same,
+            // we can provide the value that we bound.
+            return true;
+        }
+
+        // Can't supply the value if this context is for a form with a different name.
+        if (FormValueSupplier.CanBind(formName!, valueType))
+        {
+            var bindingSucceeded = FormValueSupplier.TryBind(formName!, valueType, out var boundValue);
+            _bindingInfo = new BindingInfo(formName, valueType, bindingSucceeded, boundValue);
+            if (!bindingSucceeded)
+            {
+                // Report errors
+            }
+
+            return true;
+        }
+
+        return false;
+    }
+
+    void ICascadingValueComponent.Subscribe(ComponentState subscriber)
+    {
+        throw new InvalidOperationException("Form values are always fixed.");
+    }
+
+    void ICascadingValueComponent.Unsubscribe(ComponentState subscriber)
+    {
+        throw new InvalidOperationException("Form values are always fixed.");
+    }
+
+    object? ICascadingValueComponent.CurrentValue => _bindingInfo == null ?
+        throw new InvalidOperationException("Tried to access form value before it was bound.") :
+        _bindingInfo.BoundValue;
+
+    bool ICascadingValueComponent.CurrentValueIsFixed => true;
+
+    private record BindingInfo(string? FormName, Type ValueType, bool BindingResult, object? BoundValue);
 }

src/Components/Components/src/Binding/IFormValueSupplier.cs

@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace Microsoft.AspNetCore.Components.Binding;
+
+/// <summary>
+/// Binds form data valuesto a model.
+/// </summary>
+public interface IFormValueSupplier
+{
+    /// <summary>
+    /// Determines whether the specified value type can be bound.
+    /// </summary>
+    /// <param name="formName">The form name to bind data from.</param>
+    /// <param name="valueType">The <see cref="Type"/> for the value to bind.</param>
+    /// <returns><c>true</c> if the value type can be bound; otherwise, <c>false</c>.</returns>
+    bool CanBind(string formName, Type valueType);
+
+    /// <summary>
+    /// Tries to bind the form with the specified name to a value of the specified type.
+    /// </summary>
+    /// <param name="formName">The form name to bind data from.</param>
+    /// <param name="valueType">The <see cref="Type"/> for the value to bind.</param>
+    /// <param name="boundValue">The bound value if succeeded.</param>
+    /// <returns><c>true</c> if the form was bound successfully; otherwise, <c>false</c>.</returns>
+    bool TryBind(string formName, Type valueType, [NotNullWhen(true)] out object? boundValue);
+}

src/Components/Components/src/Binding/ModelBindingContext.cs

@@ -34,4 +34,7 @@ internal ModelBindingContext(string name, string bindingContextId)
     /// The computed identifier used to determine what parts of the app can bind data.
     /// </summary>
     public string BindingContextId { get; }
+
+    internal static string Combine(ModelBindingContext? parentContext, string name) =>
+        string.IsNullOrEmpty(parentContext?.Name) ? name : $"{parentContext.Name}.{name}";
 }

src/Components/Components/src/CascadingParameterState.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Concurrent;
 using System.Diagnostics.CodeAnalysis;
+using System.Linq;
 using System.Reflection;
 using Microsoft.AspNetCore.Components.Reflection;
 using Microsoft.AspNetCore.Components.Rendering;
@@ -45,11 +46,8 @@ public static IReadOnlyList<CascadingParameterState> FindCascadingParameters(Com
             var supplier = GetMatchingCascadingValueSupplier(info, componentState);
             if (supplier != null)
             {
-                if (resultStates == null)
-                {
-                    // Although not all parameters might be matched, we know the maximum number
-                    resultStates = new List<CascadingParameterState>(infos.Length - infoIndex);
-                }
+                // Although not all parameters might be matched, we know the maximum number
+                resultStates ??= new List<CascadingParameterState>(infos.Length - infoIndex);
 
                 resultStates.Add(new CascadingParameterState(info.ConsumerValueName, supplier));
             }
@@ -98,16 +96,25 @@ private static ReflectedCascadingParameterInfo[] CreateReflectedCascadingParamet
             var attribute = prop.GetCustomAttribute<CascadingParameterAttribute>();
             if (attribute != null)
             {
-                if (result == null)
-                {
-                    result = new List<ReflectedCascadingParameterInfo>();
-                }
+                result ??= new List<ReflectedCascadingParameterInfo>();
 
                 result.Add(new ReflectedCascadingParameterInfo(
                     prop.Name,
                     prop.PropertyType,
                     attribute.Name));
             }
+
+            var hostParameterAttribute = prop.GetCustomAttributes()
+                .OfType<IHostEnvironmentCascadingParameter>().SingleOrDefault();
+            if (hostParameterAttribute != null)
+            {
+                result ??= new List<ReflectedCascadingParameterInfo>();
+
+                result.Add(new ReflectedCascadingParameterInfo(
+                    prop.Name,
+                    prop.PropertyType,
+                    hostParameterAttribute.Name));
+            }
         }
 
         return result?.ToArray() ?? Array.Empty<ReflectedCascadingParameterInfo>();

src/Components/Components/src/IHostEnvironmentCascadingParameter.cs

@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.Components;
+
+// Marks a cascading parameter that can be offered via an attribute that is not
+// directly defined in the Components assembly. For example [SupplyParameterFromForm].
+internal interface IHostEnvironmentCascadingParameter
+{
+    public string? Name { get; set; }
+}

src/Components/Components/src/PublicAPI.Unshipped.txt

@@ -1,5 +1,8 @@
 #nullable enable
 abstract Microsoft.AspNetCore.Components.RenderModeAttribute.Mode.get -> Microsoft.AspNetCore.Components.IComponentRenderMode!
+Microsoft.AspNetCore.Components.Binding.IFormValueSupplier
+Microsoft.AspNetCore.Components.Binding.IFormValueSupplier.CanBind(string! formName, System.Type! valueType) -> bool
+Microsoft.AspNetCore.Components.Binding.IFormValueSupplier.TryBind(string! formName, System.Type! valueType, out object? boundValue) -> bool
 Microsoft.AspNetCore.Components.CascadingModelBinder
 Microsoft.AspNetCore.Components.CascadingModelBinder.CascadingModelBinder() -> void
 Microsoft.AspNetCore.Components.CascadingModelBinder.ChildContent.get -> Microsoft.AspNetCore.Components.RenderFragment<Microsoft.AspNetCore.Components.ModelBindingContext!>!

src/Components/Components/src/Reflection/ComponentProperties.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Concurrent;
 using System.Diagnostics.CodeAnalysis;
+using System.Linq;
 using System.Reflection;
 using static Microsoft.AspNetCore.Internal.LinkerFlags;
 
@@ -168,11 +169,14 @@ private static void ThrowForUnknownIncomingParameterName([DynamicallyAccessedMem
         var propertyInfo = targetType.GetProperty(parameterName, BindablePropertyFlags);
         if (propertyInfo != null)
         {
-            if (!propertyInfo.IsDefined(typeof(ParameterAttribute)) && !propertyInfo.IsDefined(typeof(CascadingParameterAttribute)))
+            if (!propertyInfo.IsDefined(typeof(ParameterAttribute)) &&
+                !propertyInfo.IsDefined(typeof(CascadingParameterAttribute)) &&
+                !propertyInfo.GetCustomAttributes().OfType<IHostEnvironmentCascadingParameter>().Any())
             {
                 throw new InvalidOperationException(
                     $"Object of type '{targetType.FullName}' has a property matching the name '{parameterName}', " +
-                    $"but it does not have [{nameof(ParameterAttribute)}] or [{nameof(CascadingParameterAttribute)}] applied.");
+                    $"but it does not have [{nameof(ParameterAttribute)}], [{nameof(CascadingParameterAttribute)}] or " +
+                    $"[SupplyParameterFromFormAttribute] applied.");
             }
             else
             {
@@ -257,9 +261,30 @@ public WritersForType([DynamicallyAccessedMembers(Component)] Type targetType)
 
             foreach (var propertyInfo in GetCandidateBindableProperties(targetType))
             {
-                var parameterAttribute = propertyInfo.GetCustomAttribute<ParameterAttribute>();
-                var cascadingParameterAttribute = propertyInfo.GetCustomAttribute<CascadingParameterAttribute>();
-                var isParameter = parameterAttribute != null || cascadingParameterAttribute != null;
+                ParameterAttribute? parameterAttribute = null;
+                CascadingParameterAttribute? cascadingParameterAttribute = null;
+                IHostEnvironmentCascadingParameter? hostEnvironmentCascadingParameter = null;
+
+                var attributes = propertyInfo.GetCustomAttributes();
+                foreach (var attribute in attributes)
+                {
+                    switch (attribute)
+                    {
+                        case ParameterAttribute parameter:
+                            parameterAttribute = parameter;
+                            break;
+                        case CascadingParameterAttribute cascadingParameter:
+                            cascadingParameterAttribute = cascadingParameter;
+                            break;
+                        case IHostEnvironmentCascadingParameter hostEnvironmentAttribute:
+                            hostEnvironmentCascadingParameter = hostEnvironmentAttribute;
+                            break;
+                        default:
+                            break;
+                    }
+                }
+
+                var isParameter = parameterAttribute != null || cascadingParameterAttribute != null || hostEnvironmentCascadingParameter != null;
                 if (!isParameter)
                 {
                     continue;
@@ -274,7 +299,7 @@ public WritersForType([DynamicallyAccessedMembers(Component)] Type targetType)
 
                 var propertySetter = new PropertySetter(targetType, propertyInfo)
                 {
-                    Cascading = cascadingParameterAttribute != null,
+                    Cascading = cascadingParameterAttribute != null || hostEnvironmentCascadingParameter != null,
                 };
 
                 if (_underlyingWriters.ContainsKey(propertyName))

src/Components/Components/test/CascadingModelBinderTest.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Diagnostics.CodeAnalysis;
+using Microsoft.AspNetCore.Components.Binding;
 using Microsoft.AspNetCore.Components.Rendering;
 using Microsoft.AspNetCore.Components.Test.Helpers;
 using Microsoft.Extensions.DependencyInjection;
@@ -18,6 +19,7 @@ public CascadingModelBinderTest()
         var serviceCollection = new ServiceCollection();
         _navigationManager = new TestNavigationManager();
         serviceCollection.AddSingleton<NavigationManager>(_navigationManager);
+        serviceCollection.AddSingleton<IFormValueSupplier, TestFormValueSupplier>();
         var services = serviceCollection.BuildServiceProvider();
         _renderer = new TestRenderer(services);
     }
@@ -328,4 +330,18 @@ public TestComponent(RenderFragment renderFragment)
         protected override void BuildRenderTree(RenderTreeBuilder builder)
             => _renderFragment(builder);
     }
+
+    private class TestFormValueSupplier : IFormValueSupplier
+    {
+        public bool CanBind(string formName, Type valueType)
+        {
+            return false;
+        }
+
+        public bool TryBind(string formName, Type valueType, [NotNullWhen(true)] out object boundValue)
+        {
+            boundValue = null;
+            return false;
+        }
+    }
 }