Eliminate unused binding context ID concept

Author: SteveSandersonMS

src/Components/Web/src/Forms/EditForm.cs

@@ -78,17 +78,14 @@ public EditContext? EditContext
     /// </summary>
     [Parameter] public EventCallback<EditContext> OnInvalidSubmit { get; set; }
 
-    [CascadingParameter] private FormMappingContext? BindingContext { get; set; }
+    [CascadingParameter] private FormMappingContext? MappingContext { get; set; }
 
     /// <summary>
     /// Gets or sets the form handler name. This is not used by interactive forms.
     /// It is only used when posting to a server-side endpoint.
     /// </summary>
-    /// <remarks>
     [Parameter] public string? FormHandlerName { get; set; }
 
-    [Inject] private NavigationManager? TempNav { get; set; } // TODO: Remove
-
     /// <inheritdoc />
     protected override void OnParametersSet()
     {
@@ -133,9 +130,8 @@ protected override void BuildRenderTree(RenderTreeBuilder builder)
 
         builder.OpenElement(0, "form");
 
-        if (BindingContext != null)
+        if (MappingContext != null)
         {
-            // TODO: Remove bindingcontext.id concept
             builder.AddAttribute(2, "method", "post");
         }
 
@@ -144,11 +140,11 @@ protected override void BuildRenderTree(RenderTreeBuilder builder)
 
         // In SSR cases, we register onsubmit as a named event and emit other child elements
         // to include the handler and antiforgery token in the post data
-        if (BindingContext != null)
+        if (MappingContext != null)
         {
-            var submitEventName = CombineStrings(BindingContext.Name, FormHandlerName) ?? string.Empty;
-            builder.AddNamedEvent(5, "onsubmit", submitEventName);
-            RenderSSRFormHandlingChildren(builder, 6, submitEventName);
+            var combinedFormName = MappingContext.GetCombinedFormName(FormHandlerName) ?? string.Empty;
+            builder.AddNamedEvent(5, "onsubmit", combinedFormName);
+            RenderSSRFormHandlingChildren(builder, 6, combinedFormName);
         }
 
         builder.OpenComponent<CascadingValue<EditContext>>(7);
@@ -162,9 +158,6 @@ protected override void BuildRenderTree(RenderTreeBuilder builder)
         builder.CloseRegion();
     }
 
-    private static string? CombineStrings(string? a, string? b)
-        => string.IsNullOrEmpty(a) ? b : string.IsNullOrEmpty(b) ? a : $"{a}.{b}";
-
     private void RenderSSRFormHandlingChildren(RenderTreeBuilder builder, int sequence, string submitEventName)
     {
         builder.OpenRegion(sequence);

src/Components/Web/src/Forms/Mapping/FormMappingContext.cs

@@ -14,33 +14,17 @@ public sealed class FormMappingContext
     private List<KeyValuePair<string, FormMappingError>>? _pendingErrors;
     private Dictionary<string, Dictionary<string, FormMappingError>>? _errorsByFormName;
 
-    internal FormMappingContext(string name, string mappingContextId)
+    internal FormMappingContext(string name)
     {
         ArgumentNullException.ThrowIfNull(name);
-        ArgumentNullException.ThrowIfNull(mappingContextId);
-        // We are initializing the root context, that can be a "named" root context, or the default context.
-        // A named root context only provides a name, and that acts as the MappingId
-        // A "default" root context does not provide a name, and instead it provides an explicit Mapping ID.
-        // The explicit mapping ID matches that of the default handler, which is the URL Path.
-        if (string.IsNullOrEmpty(name) ^ string.IsNullOrEmpty(mappingContextId))
-        {
-            throw new InvalidOperationException("A root mapping context needs to provide a name and explicit mapping context id or none.");
-        }
-
         Name = name;
-        MappingContextId = mappingContextId ?? name;
     }
 
     /// <summary>
     /// The context name.
     /// </summary>
     public string Name { get; }
 
-    /// <summary>
-    /// The computed identifier used to determine what parts of the app can map data.
-    /// </summary>
-    public string MappingContextId { get; }
-
     /// <summary>
     /// Retrieves the list of errors for a given model key.
     /// </summary>
@@ -108,8 +92,17 @@ public IEnumerable<FormMappingError> GetAllErrors(string formName)
         _errorsByFormName?.TryGetValue(formName, out var formErrors) == true &&
             formErrors.TryGetValue(key, out var mappingError) ? mappingError.AttemptedValue : null;
 
-    internal static string Combine(FormMappingContext? parentContext, string name) =>
-        string.IsNullOrEmpty(parentContext?.Name) ? name : $"{parentContext.Name}.{name}";
+    internal string GetCombinedFormName(string? formHandlerName)
+    {
+        if (string.IsNullOrEmpty(Name))
+        {
+            return string.IsNullOrEmpty(formHandlerName) ? string.Empty : formHandlerName;
+        }
+        else
+        {
+            return string.IsNullOrEmpty(formHandlerName) ? Name : $"{Name}.{formHandlerName}";
+        }
+    }
 
     internal void AddError(string key, FormattableString error, string? attemptedValue)
     {

src/Components/Web/src/Forms/Mapping/FormMappingScope.cs

@@ -8,7 +8,7 @@
 namespace Microsoft.AspNetCore.Components.Forms;
 
 /// <summary>
-/// Defines the mapping context for data received from form posts.
+/// Defines the mapping scope for data received from form posts.
 /// </summary>
 public sealed class FormMappingScope : ICascadingValueSupplier, IComponent
 {
@@ -17,19 +17,15 @@ public sealed class FormMappingScope : ICascadingValueSupplier, IComponent
     private bool _hasPendingQueuedRender;
 
     /// <summary>
-    /// The mapping context name.
+    /// The mapping scope name.
     /// </summary>
-    [Parameter] public string Name { get; set; } = "";
+    [Parameter, EditorRequired] public string Name { get; set; } = default!;
 
     /// <summary>
     /// Specifies the content to be rendered inside this <see cref="FormMappingScope"/>.
     /// </summary>
     [Parameter] public RenderFragment<FormMappingContext> ChildContent { get; set; } = default!;
 
-    [CascadingParameter] private FormMappingContext? ParentContext { get; set; }
-
-    [Inject] internal NavigationManager Navigation { get; set; } = null!;
-
     [Inject] internal IFormValueMapper? FormValueModelBinder { get; set; } // Nonnull only on platforms that support HTTP form posts
 
     void IComponent.Attach(RenderHandle renderHandle)
@@ -40,16 +36,17 @@ void IComponent.Attach(RenderHandle renderHandle)
     Task IComponent.SetParametersAsync(ParameterView parameters)
     {
         parameters.SetParameterProperties(this);
-        if (ParentContext != null && string.IsNullOrEmpty(Name))
-        {
-            throw new InvalidOperationException($"Nested form mapping contexts must define a Name. (Parent context) = '{ParentContext.Name}'.");
-        }
 
         if (_cascadingValueSupplier is null)
         {
-            _cascadingValueSupplier = new SupplyParameterFromFormValueProvider(FormValueModelBinder, Navigation, ParentContext, Name);
+            if (string.IsNullOrEmpty(Name))
+            {
+                throw new InvalidOperationException($"The {nameof(FormMappingScope)} component requires a nonempty {nameof(Name)} parameter value.");
+            }
+
+            _cascadingValueSupplier = new SupplyParameterFromFormValueProvider(FormValueModelBinder, Name);
         }
-        else if (!string.Equals(Name, _cascadingValueSupplier.Name))
+        else if (!string.Equals(Name, _cascadingValueSupplier.MappingScopeName))
         {
             throw new InvalidOperationException($"{nameof(FormMappingScope)} '{nameof(Name)}' can't change after initialization.");
         }

src/Components/Web/src/Forms/Mapping/SupplyParameterFromFormServiceCollectionExtensions.cs

@@ -22,8 +22,7 @@ public static IServiceCollection AddSupplyValueFromFormProvider(this IServiceCol
         {
             return new SupplyParameterFromFormValueProvider(
                 services.GetRequiredService<IFormValueMapper>(),
-                services.GetRequiredService<NavigationManager>(),
-                null, "");
+                mappingScopeName: "");
         }));
 
         return serviceCollection;

src/Components/Web/src/Forms/Mapping/SupplyParameterFromFormValueProvider.cs

@@ -6,47 +6,26 @@
 
 namespace Microsoft.AspNetCore.Components.Forms.Mapping;
 
+// Provides values for [SupplyParameterFromForm] parameters on components.
+// It is used in two ways:
+// - By default, an instance is registered in DI, supplying values outside any FormMappingScope
+// - If there is a FormMappingScope, internally it creates an instance of this to implement ICascadingValueSupplier for it
 internal class SupplyParameterFromFormValueProvider : ICascadingValueSupplier
 {
-    private readonly FormMappingContext _mappingContext;
     private readonly IFormValueMapper? _formValueMapper;
+    private readonly FormMappingContext _mappingContext;
 
     public FormMappingContext MappingContext => _mappingContext;
 
-    public SupplyParameterFromFormValueProvider(IFormValueMapper? formValueMapper, NavigationManager navigation, FormMappingContext? parentContext, string thisName)
+    public SupplyParameterFromFormValueProvider(IFormValueMapper? formValueMapper, string mappingScopeName)
     {
-        ArgumentNullException.ThrowIfNull(navigation);
-
         _formValueMapper = formValueMapper;
-        Name = thisName;
-
-        // MappingContextId: action parameter used to define the handler
-        // Name: form name and context used to map
-        // Cases:
-        // 1) No name ("")
-        // Name = "";
-        // MappingContextId = "";
-        // <form name="" action="" />
-        // 2) Name provided
-        // Name = "my-handler";
-        // MappingContextId = <<base-relative-uri>>((<<existing-query>>&)|?)handler=my-handler
-        // <form name="my-handler" action="relative/path?existing=value&handler=my-handler
-        // 3) Parent has a name "parent-name"
-        // Name = "parent-name.my-handler";
-        // MappingContextId = <<base-relative-uri>>((<<existing-query>>&)|?)handler=my-handler
-        var name = FormMappingContext.Combine(parentContext, thisName);
-        var mappingId = string.IsNullOrEmpty(name) ? "" : GenerateMappingContextId(name);
-        _mappingContext = new FormMappingContext(name, mappingId);
-
-        string GenerateMappingContextId(string name)
-        {
-            var mappingId = navigation.ToBaseRelativePath(navigation.GetUriWithQueryParameter("handler", name));
-            var hashIndex = mappingId.IndexOf('#');
-            return hashIndex == -1 ? mappingId : new string(mappingId.AsSpan(0, hashIndex));
-        }
+        _mappingContext = new FormMappingContext(mappingScopeName);
+
+        MappingScopeName = mappingScopeName;
     }
 
-    public string Name { get; }
+    public string MappingScopeName { get; }
 
     bool ICascadingValueSupplier.IsFixed => true;
 
@@ -59,10 +38,10 @@ public bool CanSupplyValue(in CascadingParameterInfo parameterInfo)
         }
 
         // We also supply values for [SupplyValueFromForm]
-        if (_formValueMapper is not null && parameterInfo.Attribute is SupplyParameterFromFormAttribute)
+        if (_formValueMapper is not null && parameterInfo.Attribute is SupplyParameterFromFormAttribute supplyParameterFromFormAttribute)
         {
-            var (formName, valueType) = GetFormNameAndValueType(_mappingContext, parameterInfo);
-            return _formValueMapper.CanMap(valueType, formName);
+            var combinedFormName = _mappingContext.GetCombinedFormName(supplyParameterFromFormAttribute.Handler);
+            return _formValueMapper.CanMap(parameterInfo.PropertyType, combinedFormName);
         }
 
         return false;
@@ -77,9 +56,9 @@ public bool CanSupplyValue(in CascadingParameterInfo parameterInfo)
         }
 
         // We also supply values for [SupplyValueFromForm]
-        if (_formValueMapper is { } valueMapper && parameterInfo.Attribute is SupplyParameterFromFormAttribute)
+        if (_formValueMapper is { } valueMapper && parameterInfo.Attribute is SupplyParameterFromFormAttribute supplyParameterFromFormAttribute)
         {
-            return GetFormPostValue(valueMapper, _mappingContext, parameterInfo);
+            return GetFormPostValue(valueMapper, _mappingContext, parameterInfo, supplyParameterFromFormAttribute);
         }
 
         throw new InvalidOperationException($"Received an unexpected attribute type {parameterInfo.Attribute.GetType()}");
@@ -91,18 +70,18 @@ void ICascadingValueSupplier.Subscribe(ComponentState subscriber, in CascadingPa
     void ICascadingValueSupplier.Unsubscribe(ComponentState subscriber, in CascadingParameterInfo parameterInfo)
         => throw new NotSupportedException(); // IsFixed = true, so the framework won't call this
 
-    internal static object? GetFormPostValue(IFormValueMapper formValueMapper, FormMappingContext? mappingContext, in CascadingParameterInfo parameterInfo)
+    internal static object? GetFormPostValue(IFormValueMapper formValueMapper, FormMappingContext? mappingContext, in CascadingParameterInfo parameterInfo, SupplyParameterFromFormAttribute supplyParameterFromFormAttribute)
     {
         Debug.Assert(mappingContext != null);
-        var (formName, valueType) = GetFormNameAndValueType(mappingContext, parameterInfo);
+        var combinedFormName = mappingContext.GetCombinedFormName(supplyParameterFromFormAttribute.Handler);
 
         var parameterName = parameterInfo.Attribute.Name ?? parameterInfo.PropertyName;
         var handler = ((SupplyParameterFromFormAttribute)parameterInfo.Attribute).Handler;
         Action<string, FormattableString, string?> errorHandler = string.IsNullOrEmpty(handler) ?
             mappingContext.AddError :
-            (name, message, value) => mappingContext.AddError(formName, parameterName, message, value);
+            (name, message, value) => mappingContext.AddError(combinedFormName, parameterName, message, value);
 
-        var context = new FormValueMappingContext(formName!, valueType, parameterName)
+        var context = new FormValueMappingContext(combinedFormName, parameterInfo.PropertyType, parameterName)
         {
             OnError = errorHandler,
             MapErrorToContainer = mappingContext.AttachParentValue
@@ -112,15 +91,4 @@ void ICascadingValueSupplier.Unsubscribe(ComponentState subscriber, in Cascading
 
         return context.Result;
     }
-
-    private static (string FormName, Type ValueType) GetFormNameAndValueType(FormMappingContext? mappingContext, in CascadingParameterInfo parameterInfo)
-    {
-        var valueType = parameterInfo.PropertyType;
-        var valueName = ((SupplyParameterFromFormAttribute)parameterInfo.Attribute).Handler;
-        var formName = string.IsNullOrEmpty(valueName) ?
-            (mappingContext?.Name) :
-            FormMappingContext.Combine(mappingContext, valueName);
-
-        return (formName!, valueType);
-    }
 }

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

@@ -25,7 +25,6 @@ Microsoft.AspNetCore.Components.Forms.FormMappingContext.GetAttemptedValue(strin
 Microsoft.AspNetCore.Components.Forms.FormMappingContext.GetAttemptedValue(string! key) -> string?
 Microsoft.AspNetCore.Components.Forms.FormMappingContext.GetErrors(string! formName, string! key) -> Microsoft.AspNetCore.Components.Forms.Mapping.FormMappingError?
 Microsoft.AspNetCore.Components.Forms.FormMappingContext.GetErrors(string! key) -> Microsoft.AspNetCore.Components.Forms.Mapping.FormMappingError?
-Microsoft.AspNetCore.Components.Forms.FormMappingContext.MappingContextId.get -> string!
 Microsoft.AspNetCore.Components.Forms.FormMappingContext.Name.get -> string!
 Microsoft.AspNetCore.Components.Forms.FormMappingScope
 Microsoft.AspNetCore.Components.Forms.FormMappingScope.ChildContent.get -> Microsoft.AspNetCore.Components.RenderFragment<Microsoft.AspNetCore.Components.Forms.FormMappingContext!>!