Forms PRG and error handling fixes (#49472)

* Add some E2E test app code that demonstrates problems (no actual E2E test scripts yet though)

* Fix one of the problems (streaming SSR wasn't returning synchronous errors)

* Fix event dispatch error handling

* E2E cases

* Fix and test for P/R/G

* Renames from other PR review

Author: SteveSandersonMS

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

@@ -102,7 +102,7 @@ static Microsoft.Extensions.DependencyInjection.CascadingValueServiceCollectionE
 virtual Microsoft.AspNetCore.Components.Rendering.ComponentState.DisposeAsync() -> System.Threading.Tasks.ValueTask
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.AddPendingTask(Microsoft.AspNetCore.Components.Rendering.ComponentState? componentState, System.Threading.Tasks.Task! task) -> void
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.CreateComponentState(int componentId, Microsoft.AspNetCore.Components.IComponent! component, Microsoft.AspNetCore.Components.Rendering.ComponentState? parentComponentState) -> Microsoft.AspNetCore.Components.Rendering.ComponentState!
-virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.DispatchEventAsync(ulong eventHandlerId, Microsoft.AspNetCore.Components.RenderTree.EventFieldInfo? fieldInfo, System.EventArgs! eventArgs, bool quiesce) -> System.Threading.Tasks.Task!
+virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.DispatchEventAsync(ulong eventHandlerId, Microsoft.AspNetCore.Components.RenderTree.EventFieldInfo? fieldInfo, System.EventArgs! eventArgs, bool waitForQuiescence) -> System.Threading.Tasks.Task!
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.ResolveComponentForRenderMode(System.Type! componentType, int? parentComponentId, Microsoft.AspNetCore.Components.IComponentActivator! componentActivator, Microsoft.AspNetCore.Components.IComponentRenderMode! renderMode) -> Microsoft.AspNetCore.Components.IComponent!
 ~Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrame.ComponentRenderMode.get -> Microsoft.AspNetCore.Components.IComponentRenderMode
 ~Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrame.NamedEventAssignedName.get -> string

src/Components/Components/src/RenderTree/Renderer.cs

@@ -380,7 +380,7 @@ protected virtual ComponentState CreateComponentState(int componentId, IComponen
     /// </returns>
     public virtual Task DispatchEventAsync(ulong eventHandlerId, EventFieldInfo? fieldInfo, EventArgs eventArgs)
     {
-        return DispatchEventAsync(eventHandlerId, fieldInfo, eventArgs, quiesce: false);
+        return DispatchEventAsync(eventHandlerId, fieldInfo, eventArgs, waitForQuiescence: false);
     }
 
     /// <summary>
@@ -389,15 +389,20 @@ public virtual Task DispatchEventAsync(ulong eventHandlerId, EventFieldInfo? fie
     /// <param name="eventHandlerId">The <see cref="RenderTreeFrame.AttributeEventHandlerId"/> value from the original event attribute.</param>
     /// <param name="eventArgs">Arguments to be passed to the event handler.</param>
     /// <param name="fieldInfo">Information that the renderer can use to update the state of the existing render tree to match the UI.</param>
-    /// <param name="quiesce">Whether to wait for quiescence or not.</param>
+    /// <param name="waitForQuiescence">A flag indicating whether to wait for quiescence.</param>
     /// <returns>
     /// A <see cref="Task"/> which will complete once all asynchronous processing related to the event
     /// has completed.
     /// </returns>
-    public virtual Task DispatchEventAsync(ulong eventHandlerId, EventFieldInfo? fieldInfo, EventArgs eventArgs, bool quiesce)
+    public virtual Task DispatchEventAsync(ulong eventHandlerId, EventFieldInfo? fieldInfo, EventArgs eventArgs, bool waitForQuiescence)
     {
         Dispatcher.AssertAccess();
 
+        if (waitForQuiescence)
+        {
+            _pendingTasks ??= new();
+        }
+
         var callback = GetRequiredEventCallback(eventHandlerId);
         Log.HandlingEvent(_logger, eventHandlerId, eventArgs);
 
@@ -425,22 +430,9 @@ public virtual Task DispatchEventAsync(ulong eventHandlerId, EventFieldInfo? fie
             _isBatchInProgress = true;
 
             task = callback.InvokeAsync(eventArgs);
-            if (quiesce)
-            {
-                // If we are waiting for quiescence, the quiescence task will capture any async exception.
-                // If the exception is thrown synchronously, we just want it to flow to the callers, and
-                // not go through the ErrorBoundary.
-                _pendingTasks ??= new();
-                AddPendingTask(receiverComponentState, task);
-            }
         }
         catch (Exception e)
         {
-            if (quiesce)
-            {
-                // Exception filters are not AoT friendly.
-                throw;
-            }
             HandleExceptionViaErrorBoundary(e, receiverComponentState);
             return Task.CompletedTask;
         }
@@ -453,15 +445,19 @@ public virtual Task DispatchEventAsync(ulong eventHandlerId, EventFieldInfo? fie
             ProcessPendingRender();
         }
 
-        if (quiesce)
+        // Task completed synchronously or is still running. We already processed all of the rendering
+        // work that was queued so let our error handler deal with it.
+        var errorHandledTask = GetErrorHandledTask(task, receiverComponentState);
+
+        if (waitForQuiescence)
         {
+            AddPendingTask(receiverComponentState, errorHandledTask);
             return WaitForQuiescence();
         }
-
-        // Task completed synchronously or is still running. We already processed all of the rendering
-        // work that was queued so let our error handler deal with it.
-        var result = GetErrorHandledTask(task, receiverComponentState);
-        return result;
+        else
+        {
+            return errorHandledTask;
+        }
     }
 
     /// <summary>

src/Components/Endpoints/src/FormMapping/HttpContextFormValueMapper.cs

@@ -73,7 +73,7 @@ private static bool MatchesScope(string incomingScopeQualifiedFormName, string c
     public void Map(FormValueMappingContext context)
     {
         // This will func to a proper binder
-        if (!CanMap(context.ValueType, context.MappingScopeName, context.RestrictToFormName))
+        if (!CanMap(context.ValueType, context.AcceptMappingScopeName, context.AcceptFormName))
         {
             context.SetResult(null);
         }

src/Components/Endpoints/src/RazorComponentEndpointInvoker.cs

@@ -77,16 +77,29 @@ await EndpointHtmlRenderer.InitializeStandardComponentServicesAsync(
             ParameterView.Empty,
             waitForQuiescence: isPost);
 
-        var isBadRequest = false;
-        var quiesceTask = isPost ? _renderer.DispatchSubmitEventAsync(handler, out isBadRequest) : htmlContent.QuiescenceTask;
-        if (isBadRequest)
+        Task quiesceTask;
+        if (!isPost)
         {
-            return;
+            quiesceTask = htmlContent.QuiescenceTask;
         }
-
-        if (isPost)
+        else
         {
-            await Task.WhenAll(_renderer.NonStreamingPendingTasks);
+            try
+            {
+                var isBadRequest = false;
+                quiesceTask = _renderer.DispatchSubmitEventAsync(handler, out isBadRequest);
+                if (isBadRequest)
+                {
+                    return;
+                }
+
+                await Task.WhenAll(_renderer.NonStreamingPendingTasks);
+            }
+            catch (NavigationException ex)
+            {
+                await EndpointHtmlRenderer.HandleNavigationException(_context, ex);
+                quiesceTask = Task.CompletedTask;
+            }
         }
 
         // Importantly, we must not yield this thread (which holds exclusive access to the renderer sync context)
@@ -95,7 +108,7 @@ await EndpointHtmlRenderer.InitializeStandardComponentServicesAsync(
         // renderer sync context and cause a batch that would get missed.
         htmlContent.WriteTo(writer, HtmlEncoder.Default); // Don't use WriteToAsync, as per the comment above
 
-        if (!quiesceTask.IsCompleted)
+        if (!quiesceTask.IsCompletedSuccessfully)
         {
             await _renderer.SendStreamingUpdatesAsync(_context, quiesceTask, writer);
         }

src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.EventDispatch.cs

@@ -48,7 +48,7 @@ internal Task DispatchSubmitEventAsync(string? handlerName, out bool isBadReques
         var frameLocation = locationsForName.Single();
         var eventHandlerId = FindEventHandlerIdForNamedEvent("onsubmit", frameLocation.ComponentId, frameLocation.FrameIndex);
         return eventHandlerId.HasValue
-            ? DispatchEventAsync(eventHandlerId.Value, null, EventArgs.Empty, quiesce: true)
+            ? DispatchEventAsync(eventHandlerId.Value, null, EventArgs.Empty, waitForQuiescence: true)
             : Task.CompletedTask;
     }
 

src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.Prerendering.cs

@@ -133,7 +133,7 @@ private async Task WaitForResultReady(bool waitForQuiescence, PrerenderedCompone
         }
     }
 
-    private static ValueTask<PrerenderedComponentHtmlContent> HandleNavigationException(HttpContext httpContext, NavigationException navigationException)
+    public static ValueTask<PrerenderedComponentHtmlContent> HandleNavigationException(HttpContext httpContext, NavigationException navigationException)
     {
         if (httpContext.Response.HasStarted)
         {

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

@@ -13,31 +13,31 @@ public class FormValueMappingContext
     /// <summary>
     /// Initializes a new instance of <see cref="FormValueMappingContext"/>.
     /// </summary>
-    /// <param name="mappingScopeName">The name of the current <see cref="FormMappingScope"/>. Values will only be mapped if the incoming data corresponds to this scope name.</param>
-    /// <param name="restrictToFormName">If set, indicates that the mapping should only receive values if the incoming form matches this name. If null, the mapping should receive data from any form in the mapping scope.</param>
+    /// <param name="acceptMappingScopeName">The name of a <see cref="FormMappingScope"/>. Values will only be mapped if the incoming data corresponds to this scope name.</param>
+    /// <param name="acceptFormName">If set, indicates that the mapping should only receive values if the incoming form matches this name. If null, the mapping should receive data from any form in the mapping scope.</param>
     /// <param name="valueType">The <see cref="Type"/> of the value to map.</param>
     /// <param name="parameterName">The name of the parameter to map data to.</param>
-    public FormValueMappingContext(string mappingScopeName, string? restrictToFormName, Type valueType, string parameterName)
+    public FormValueMappingContext(string acceptMappingScopeName, string? acceptFormName, Type valueType, string parameterName)
     {
-        ArgumentNullException.ThrowIfNull(mappingScopeName, nameof(mappingScopeName));
+        ArgumentNullException.ThrowIfNull(acceptMappingScopeName, nameof(acceptMappingScopeName));
         ArgumentNullException.ThrowIfNull(valueType, nameof(valueType));
         ArgumentNullException.ThrowIfNull(parameterName, nameof(parameterName));
 
-        MappingScopeName = mappingScopeName;
-        RestrictToFormName = restrictToFormName;
+        AcceptMappingScopeName = acceptMappingScopeName;
+        AcceptFormName = acceptFormName;
         ParameterName = parameterName;
         ValueType = valueType;
     }
 
     /// <summary>
-    /// Gets the name of the current <see cref="FormMappingScope"/>.
+    /// Gets the name of <see cref="FormMappingScope"/> that is allowed to supply data in this context.
     /// </summary>
-    public string MappingScopeName { get; }
+    public string AcceptMappingScopeName { get; }
 
     /// <summary>
     /// If set, indicates that the mapping should only receive values if the incoming form matches this name. If null, the mapping should receive data from any form in the mapping scope.
     /// </summary>
-    public string? RestrictToFormName { get; }
+    public string? AcceptFormName { get; }
 
     /// <summary>
     /// Gets the name of the parameter to map data to.

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

@@ -42,14 +42,14 @@ Microsoft.AspNetCore.Components.Forms.Mapping.FormMappingError.ErrorMessages.get
 Microsoft.AspNetCore.Components.Forms.Mapping.FormMappingError.Name.get -> string!
 Microsoft.AspNetCore.Components.Forms.Mapping.FormMappingError.Path.get -> string!
 Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext
-Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.FormValueMappingContext(string! mappingScopeName, string? restrictToFormName, System.Type! valueType, string! parameterName) -> void
+Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.AcceptFormName.get -> string?
+Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.AcceptMappingScopeName.get -> string!
+Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.FormValueMappingContext(string! acceptMappingScopeName, string? acceptFormName, System.Type! valueType, string! parameterName) -> void
 Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.MapErrorToContainer.get -> System.Action<string!, object!>?
 Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.MapErrorToContainer.set -> void
-Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.MappingScopeName.get -> string!
 Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.OnError.get -> System.Action<string!, System.FormattableString!, string?>?
 Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.OnError.set -> void
 Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.ParameterName.get -> string!
-Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.RestrictToFormName.get -> string?
 Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.Result.get -> object?
 Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.SetResult(object? result) -> void
 Microsoft.AspNetCore.Components.Forms.Mapping.FormValueMappingContext.ValueType.get -> System.Type!