[release/9.0] [Blazor] Invoke inbound activity handlers on circuit initialization (dotnet#57678)

Backport of dotnet#57557 to release/9.0

# [Blazor] Invoke inbound activity handlers on circuit initialization

Fixes an issue where inbound activity handlers don't get invoked on circuit initialization.

> [!NOTE]
> This bug only affects Blazor Server apps, _not_ Blazor Web apps utilizing server interactivity

## Description

Inbound activity handlers were added in .NET 8 to enable:
* Monitoring inbound circuit activity
* Enabling server-side Blazor services to be [accessed from a different DI scope](https://learn.microsoft.com/aspnet/core/blazor/fundamentals/dependency-injection?view=aspnetcore-8.0#access-server-side-blazor-services-from-a-different-di-scope)

However, prior to the fix in this PR, this feature didn't apply to the first interactive render after the initial page load. This means that when utilizing this feature to access Blazor services from a different DI scope, the service might only become accessible after subsequent renders, not the initial render.

This PR makes the following changes:
* Updated `CircuitHost` to invoke inbound activity handlers on circuit initialization
* Added an extra test to verify that inbound activity handlers work on the initial page load
* Updated existing Blazor Web tests to reuse test logic from the non-web tests
  * This helps to ensure that the feature works the same way on Blazor Server and Blazor Web

Fixes dotnet#57481

## Customer Impact

The [initial issue report](dotnet#57481) was from a customer who was impacted experiencing this problem in their app. The problem does not inherently cause an app to stop working, but if the application code has made the (rightful) assumption that the service accessor is initialized, then session may crash. The workaround is to upgrade the app to use the "Blazor Web App" pattern, although this can be a fairly large change.

## Regression?

- [ ] Yes
- [X] No

The problem has existed since the introduction of the feature in .NET 8.
## Risk

- [ ] High
- [ ] Medium
- [X] Low

The change is straightforward, and new tests have been added to ensure that it addresses the issue. Existing tests verify that a new regression is not introduced.
## Verification

- [X] Manual (required)
- [X] Automated

## Packaging changes reviewed?

- [ ] Yes
- [ ] No
- [x] N/A

Author: github-actions[bot]

src/Components/Server/src/Circuits/CircuitHost.cs

@@ -104,7 +104,7 @@ public Task InitializeAsync(ProtectedPrerenderComponentApplicationStore store, C
     {
         Log.InitializationStarted(_logger);
 
-        return Renderer.Dispatcher.InvokeAsync(async () =>
+        return HandleInboundActivityAsync(() => Renderer.Dispatcher.InvokeAsync(async () =>
         {
             if (_initialized)
             {
@@ -165,7 +165,7 @@ public Task InitializeAsync(ProtectedPrerenderComponentApplicationStore store, C
                 UnhandledException?.Invoke(this, new UnhandledExceptionEventArgs(ex, isTerminating: false));
                 await TryNotifyClientErrorAsync(Client, GetClientErrorMessage(ex), ex);
             }
-        });
+        }));
     }
 
     // We handle errors in DisposeAsync because there's no real value in letting it propagate.

src/Components/test/E2ETest/ServerExecutionTests/CircuitContextTest.cs

@@ -22,28 +22,39 @@ public CircuitContextTest(
     {
     }
 
-    protected override void InitializeAsyncCore()
+    [Fact]
+    public void ComponentMethods_HaveCircuitContext()
     {
         Navigate(ServerPathBase);
         Browser.MountTestComponent<CircuitContextComponent>();
-        Browser.Equal("Circuit Context", () => Browser.Exists(By.TagName("h1")).Text);
+        TestCircuitContextCore(Browser);
     }
 
     [Fact]
-    public void ComponentMethods_HaveCircuitContext()
+    public void ComponentMethods_HaveCircuitContext_OnInitialPageLoad()
     {
-        Browser.Click(By.Id("trigger-click-event-button"));
+        // https://github.com/dotnet/aspnetcore/issues/57481
+        Navigate($"{ServerPathBase}?initial-component-type={typeof(CircuitContextComponent).AssemblyQualifiedName}");
+        TestCircuitContextCore(Browser);
+    }
+
+    // Internal for reuse in Blazor Web tests
+    internal static void TestCircuitContextCore(IWebDriver browser)
+    {
+        browser.Equal("Circuit Context", () => browser.Exists(By.TagName("h1")).Text);
+
+        browser.Click(By.Id("trigger-click-event-button"));
 
-        Browser.True(() => HasCircuitContext("SetParametersAsync"));
-        Browser.True(() => HasCircuitContext("OnInitializedAsync"));
-        Browser.True(() => HasCircuitContext("OnParametersSetAsync"));
-        Browser.True(() => HasCircuitContext("OnAfterRenderAsync"));
-        Browser.True(() => HasCircuitContext("InvokeDotNet"));
-        Browser.True(() => HasCircuitContext("OnClickEvent"));
+        browser.True(() => HasCircuitContext("SetParametersAsync"));
+        browser.True(() => HasCircuitContext("OnInitializedAsync"));
+        browser.True(() => HasCircuitContext("OnParametersSetAsync"));
+        browser.True(() => HasCircuitContext("OnAfterRenderAsync"));
+        browser.True(() => HasCircuitContext("InvokeDotNet"));
+        browser.True(() => HasCircuitContext("OnClickEvent"));
 
         bool HasCircuitContext(string eventName)
         {
-            var resultText = Browser.FindElement(By.Id($"circuit-context-result-{eventName}")).Text;
+            var resultText = browser.FindElement(By.Id($"circuit-context-result-{eventName}")).Text;
             var result = bool.Parse(resultText);
             return result;
         }

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

@@ -4,6 +4,7 @@
 using Components.TestServer.RazorComponents;
 using Microsoft.AspNetCore.Components.E2ETest.Infrastructure;
 using Microsoft.AspNetCore.Components.E2ETest.Infrastructure.ServerFixtures;
+using Microsoft.AspNetCore.Components.E2ETests.ServerExecutionTests;
 using Microsoft.AspNetCore.E2ETesting;
 using OpenQA.Selenium;
 using TestServer;
@@ -1142,8 +1143,7 @@ public void NavigationManagerCanRefreshSSRPageWhenServerInteractivityEnabled()
     public void InteractiveServerRootComponent_CanAccessCircuitContext()
     {
         Navigate($"{ServerPathBase}/interactivity/circuit-context");
-
-        Browser.Equal("True", () => Browser.FindElement(By.Id("has-circuit-context")).Text);
+        CircuitContextTest.TestCircuitContextCore(Browser);
     }
 
     [Fact]

src/Components/test/testassets/BasicTestApp/Index.razor

@@ -1,4 +1,6 @@
 @using Microsoft.AspNetCore.Components.Rendering
+@using System.Web
+@inject NavigationManager NavigationManager
 <div id="test-selector">
     Select test:
     <select id="test-selector-select" @bind=SelectedComponentTypeName>
@@ -137,6 +139,15 @@
     Type SelectedComponentType
         => SelectedComponentTypeName == "none" ? null : Type.GetType(SelectedComponentTypeName, throwOnError: true);
 
+    protected override void OnInitialized()
+    {
+        var uri = new Uri(NavigationManager.Uri);
+        if (HttpUtility.ParseQueryString(uri.Query)["initial-component-type"] is { Length: > 0 } initialComponentTypeName)
+        {
+            SelectedComponentTypeName = initialComponentTypeName;
+        }
+    }
+
     void RenderSelectedComponent(RenderTreeBuilder builder)
     {
         if (SelectedComponentType != null)

src/Components/test/testassets/Components.TestServer/RazorComponents/App.razor

@@ -25,6 +25,7 @@
     </script>
     <script src="_framework/blazor.web.js" autostart="false" suppress-error="BL9992"></script>
     <script src="_content/TestContentPackage/counterInterop.js"></script>
+    <script src="js/circuitContextTest.js"></script>
     <script>
         // This is called by the Components.WasmMinimal project.
         function getQueryParam(key) {

src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/Interactivity/CircuitContextPage.razor

@@ -1,25 +1,3 @@
 @page "/interactivity/circuit-context"
-@rendermode RenderMode.InteractiveServer
-@inject TestCircuitContextAccessor CircuitContextAccessor
 
-<h1>Circuit context</h1>
-
-<p>
-    Has circuit context: <span id="has-circuit-context">@_hasCircuitContext</span>
-</p>
-
-@code {
-    private bool _hasCircuitContext;
-
-    protected override async Task OnAfterRenderAsync(bool firstRender)
-    {
-        if (firstRender)
-        {
-            await Task.Yield();
-
-            _hasCircuitContext = CircuitContextAccessor.HasCircuitContext;
-
-            StateHasChanged();
-        }
-    }
-}
+<CircuitContextComponent @rendermode="RenderMode.InteractiveServer" />