Endpoint renderer waits for quiescence with stopping the rendering

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

@@ -81,10 +81,7 @@ private Task ReturnErrorResponse(string detailedMessage)
 
     internal async Task SetNotFoundResponseAsync(string baseUri, NotFoundEventArgs args)
     {
-        if (_httpContext.Response.HasStarted ||
-            // POST waits for quiescence -> rendering the NotFoundPage would be queued for the next batch
-            // but we want to send the signal to the renderer to stop rendering future batches -> use client rendering
-            HttpMethods.IsPost(_httpContext.Request.Method))
+        if (_httpContext.Response.HasStarted)
         {
             if (string.IsNullOrEmpty(_notFoundUrl))
             {
@@ -104,7 +101,7 @@ internal async Task SetNotFoundResponseAsync(string baseUri, NotFoundEventArgs a
         // When the application triggers a NotFound event, we continue rendering the current batch.
         // However, after completing this batch, we do not want to process any further UI updates,
         // as we are going to return a 404 status and discard the UI updates generated so far.
-        SignalRendererToFinishRendering();
+        RequestRendererToFinishRendering();
     }
 
     private string GetNotFoundUrl(string baseUri, NotFoundEventArgs args)

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

@@ -149,6 +149,8 @@ internal async ValueTask<PrerenderedComponentHtmlContent> RenderEndpointComponen
             var component = BeginRenderingComponent(rootComponentType, parameters);
             var result = new PrerenderedComponentHtmlContent(Dispatcher, component);
 
+            FinishRendereingOnQuiescenceIfRequested(result);
+
             await WaitForResultReady(waitForQuiescence, result);
 
             return result;
@@ -159,6 +161,19 @@ internal async ValueTask<PrerenderedComponentHtmlContent> RenderEndpointComponen
         }
     }
 
+    private void FinishRendereingOnQuiescenceIfRequested(PrerenderedComponentHtmlContent htmlContent)
+    {
+        if (htmlContent.QuiescenceTask.IsCompleted)
+        {
+            SignalRendererToFinishRendering();
+            return;
+        }
+
+        htmlContent.QuiescenceTask.ContinueWith(
+            _ => SignalRendererToFinishRendering(),
+            TaskScheduler.Default);
+    }
+
     private async Task WaitForResultReady(bool waitForQuiescence, PrerenderedComponentHtmlContent result)
     {
         if (waitForQuiescence)

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

@@ -44,6 +44,7 @@ internal partial class EndpointHtmlRenderer : StaticHtmlRenderer, IComponentPrer
     private HttpContext _httpContext = default!; // Always set at the start of an inbound call
     private ResourceAssetCollection? _resourceCollection;
     private bool _rendererIsStopped;
+    private bool _rendererStopRequested;
     private readonly ILogger _logger;
 
     // The underlying Renderer always tracks the pending tasks representing *full* quiescence, i.e.,
@@ -185,11 +186,19 @@ protected override void AddPendingTask(ComponentState? componentState, Task task
         base.AddPendingTask(componentState, task);
     }
 
+    internal void RequestRendererToFinishRendering()
+    {
+        // requests a deferred stop of the renderer, which will have an effect after the current batch is completed
+        _rendererStopRequested = true;
+    }
+
     // For testing purposes only
     internal void SignalRendererToFinishRendering()
     {
-        // sets a deferred stop on the renderer, which will have an effect after the current batch is completed
-        _rendererIsStopped = true;
+        if (_rendererStopRequested)
+        {
+            _rendererIsStopped = true;
+        }
     }
 
     protected override void ProcessPendingRender()

src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs

@@ -141,14 +141,22 @@ public void NotFoundSetOnInitialization_ResponseNotStarted_SSR(bool hasReExecuti
         string testUrl = $"{ServerPathBase}{reexecution}/set-not-found-ssr?useCustomNotFoundPage={hasCustomNotFoundPageSet}";
         Navigate(testUrl);
 
-        if (hasCustomNotFoundPageSet)
-        {
-            AssertNotFoundPageRendered();
-        }
-        else
-        {
-            AssertNotFoundFragmentRendered();
-        }
+        AssertNotFoundRendered_ResponseNotStarted(hasCustomNotFoundPageSet);
+        AssertUrlNotChanged(testUrl);
+    }
+
+    [Theory]
+    [InlineData(true, true)]
+    [InlineData(true, false)]
+    [InlineData(false, true)]
+    [InlineData(false, false)]
+    public void NotFoundSetOnInitialization_AfterAsyncOperation_ResponseNotStarted_SSR(bool hasReExecutionMiddleware, bool hasCustomNotFoundPageSet)
+    {
+        string reexecution = hasReExecutionMiddleware ? "/reexecution" : "";
+        string testUrl = $"{ServerPathBase}{reexecution}/set-not-found-ssr?doAsync=true&useCustomNotFoundPage={hasCustomNotFoundPageSet}";
+        Navigate(testUrl);
+
+        AssertNotFoundRendered_ResponseNotStarted(hasCustomNotFoundPageSet);
         AssertUrlNotChanged(testUrl);
     }
 
@@ -162,7 +170,8 @@ public void NotFoundSetOnInitialization_ResponseStarted_SSR(bool hasReExecutionM
         string reexecution = hasReExecutionMiddleware ? "/reexecution" : "";
         string testUrl = $"{ServerPathBase}{reexecution}/set-not-found-ssr-streaming?useCustomNotFoundPage={hasCustomNotFoundPageSet}";
         Navigate(testUrl);
-        AssertNotFoundRendered_ResponseStarted_Or_POST(hasReExecutionMiddleware, hasCustomNotFoundPageSet, testUrl);
+
+        AssertNotFoundRendered_ResponseStarted(hasReExecutionMiddleware, hasCustomNotFoundPageSet, testUrl);
         AssertUrlNotChanged(testUrl);
     }
 
@@ -176,11 +185,12 @@ public void NotFoundSetOnInitialization_ResponseStarted_EnhancedNavigationDisabl
         string reexecution = hasReExecutionMiddleware ? "/reexecution" : "";
         string testUrl = $"{ServerPathBase}{reexecution}/set-not-found-ssr-streaming?useCustomNotFoundPage={hasCustomNotFoundPageSet}";
         Navigate(testUrl);
-        AssertNotFoundRendered_ResponseStarted_Or_POST(hasReExecutionMiddleware, hasCustomNotFoundPageSet, testUrl);
+
+        AssertNotFoundRendered_ResponseStarted(hasReExecutionMiddleware, hasCustomNotFoundPageSet, testUrl);
         AssertUrlChanged(testUrl);
     }
 
-    private void AssertNotFoundRendered_ResponseStarted_Or_POST(bool hasReExecutionMiddleware, bool hasCustomNotFoundPageSet, string testUrl)
+    private void AssertNotFoundRendered_ResponseStarted(bool hasReExecutionMiddleware, bool hasCustomNotFoundPageSet, string testUrl)
     {
         if (hasCustomNotFoundPageSet)
         {
@@ -197,6 +207,18 @@ private void AssertNotFoundRendered_ResponseStarted_Or_POST(bool hasReExecutionM
         }
     }
 
+    private void AssertNotFoundRendered_ResponseNotStarted(bool hasCustomNotFoundPageSet)
+    {
+        if (hasCustomNotFoundPageSet)
+        {
+            AssertNotFoundPageRendered();
+        }
+        else
+        {
+            AssertNotFoundFragmentRendered();
+        }
+    }
+
     [Theory]
     [InlineData(true, true)]
     [InlineData(true, false)]
@@ -209,7 +231,23 @@ public void NotFoundSetOnFormSubmit_ResponseNotStarted_SSR(bool hasReExecutionMi
         Navigate(testUrl);
         Browser.FindElement(By.Id("not-found-form")).FindElement(By.TagName("button")).Click();
 
-        AssertNotFoundRendered_ResponseStarted_Or_POST(hasReExecutionMiddleware, hasCustomNotFoundPageSet, testUrl);
+        AssertNotFoundRendered_ResponseStarted(hasReExecutionMiddleware, hasCustomNotFoundPageSet, testUrl);
+        AssertUrlNotChanged(testUrl);
+    }
+
+    [Theory]
+    [InlineData(true, true)]
+    [InlineData(true, false)]
+    [InlineData(false, true)]
+    [InlineData(false, false)]
+    public void NotFoundSetOnFormSubmit_AfterAsyncOperation_ResponseNotStarted_SSR(bool hasReExecutionMiddleware, bool hasCustomNotFoundPageSet)
+    {
+        string reexecution = hasReExecutionMiddleware ? "/reexecution" : "";
+        string testUrl = $"{ServerPathBase}{reexecution}/post-not-found-ssr?doAsync=true&useCustomNotFoundPage={hasCustomNotFoundPageSet}";
+        Navigate(testUrl);
+        Browser.FindElement(By.Id("not-found-form")).FindElement(By.TagName("button")).Click();
+
+        AssertNotFoundRendered_ResponseNotStarted(hasCustomNotFoundPageSet);
         AssertUrlNotChanged(testUrl);
     }
 
@@ -225,7 +263,7 @@ public void NotFoundSetOnFormSubmit_ResponseStarted_SSR(bool hasReExecutionMiddl
         Navigate(testUrl);
         Browser.FindElement(By.Id("not-found-form")).FindElement(By.TagName("button")).Click();
 
-        AssertNotFoundRendered_ResponseStarted_Or_POST(hasReExecutionMiddleware, hasCustomNotFoundPageSet, testUrl);
+        AssertNotFoundRendered_ResponseStarted(hasReExecutionMiddleware, hasCustomNotFoundPageSet, testUrl);
         AssertUrlNotChanged(testUrl);
     }
 

src/Components/test/testassets/TestContentPackage/NotFound/ComponentThatPostsNotFound.razor

@@ -1,4 +1,4 @@
-@using Microsoft.AspNetCore.Components.Forms
+@using Microsoft.AspNetCore.Components.Forms
 
 @inject NavigationManager NavigationManager
 
@@ -16,17 +16,17 @@
 
 @code{
     [Parameter]
-    public bool StartStreaming { get; set; } = false;
+    public bool DoAsyncOperationBeforeSettingNotFound { get; set; } = false;
 
     [Parameter]
     public bool WaitForInteractivity { get; set; } = false;
 
     private async Task HandleSubmit()
     {
-        if (StartStreaming)
+        if (DoAsyncOperationBeforeSettingNotFound)
         {
             await Task.Yield();
         }
         NavigationManager.NotFound();
     }
-}
+}

src/Components/test/testassets/TestContentPackage/NotFound/ComponentThatSetsNotFound.razor

@@ -1,4 +1,4 @@
-@inject NavigationManager NavigationManager
+@inject NavigationManager NavigationManager
 
 @if (!WaitForInteractivity || RendererInfo.IsInteractive)
 {
@@ -10,17 +10,17 @@
 
 @code{
     [Parameter]
-    public bool StartStreaming { get; set; } = false;
+    public bool DoAsyncOperationBeforeSettingNotFound { get; set; } = false;
 
     [Parameter]
     public bool WaitForInteractivity { get; set; } = false;
 
     protected async override Task OnInitializedAsync()
     {
-        if (StartStreaming)
+        if (DoAsyncOperationBeforeSettingNotFound)
         {
             await Task.Yield();
         }
         NavigationManager.NotFound();
     }
-}
+}

src/Components/test/testassets/TestContentPackage/NotFound/PageThatPostsNotFound-no-streaming.razor

@@ -8,4 +8,9 @@
     interactive later if interactivity was enabled in the app
 *@
 
-<TestContentPackage.NotFound.ComponentThatPostsNotFound />
+<TestContentPackage.NotFound.ComponentThatPostsNotFound DoAsyncOperationBeforeSettingNotFound="@DoAsync" />
+
+@code{
+    [SupplyParameterFromQuery(Name = "doAsync")]
+    public bool DoAsync { get; set; } = false;
+}

src/Components/test/testassets/TestContentPackage/NotFound/PageThatPostsNotFound-streaming.razor

@@ -8,4 +8,4 @@
     interactive later if interactivity was enabled in the app
 *@
 
-<TestContentPackage.NotFound.ComponentThatPostsNotFound StartStreaming="true"/>
+<TestContentPackage.NotFound.ComponentThatPostsNotFound DoAsyncOperationBeforeSettingNotFound="true"/>

src/Components/test/testassets/TestContentPackage/NotFound/PageThatSetsNotFound-no-streaming.razor

@@ -8,4 +8,9 @@
     interactive later if interactivity was enabled in the app
 *@
 
-<TestContentPackage.NotFound.ComponentThatSetsNotFound />
+<TestContentPackage.NotFound.ComponentThatSetsNotFound DoAsyncOperationBeforeSettingNotFound="@DoAsync" />
+
+@code{
+    [SupplyParameterFromQuery(Name = "doAsync")]
+    public bool DoAsync { get; set; } = false;
+}

src/Components/test/testassets/TestContentPackage/NotFound/PageThatSetsNotFound-streaming.razor

@@ -8,4 +8,4 @@
     interactive later if interactivity was enabled in the app
 *@
 
-<TestContentPackage.NotFound.ComponentThatSetsNotFound StartStreaming="true"/>
+<TestContentPackage.NotFound.ComponentThatSetsNotFound DoAsyncOperationBeforeSettingNotFound="true"/>