Use MetadataUpdater.IsSupported to determine if application supports hot reload

Fixes #33477

Author: pranavkm

src/Components/Components/src/ComponentBase.cs

@@ -102,7 +102,7 @@ protected void StateHasChanged()
                 return;
             }
 
-            if (_hasNeverRendered || ShouldRender() || _renderHandle.IsHotReloading)
+            if (_hasNeverRendered || ShouldRender() || _renderHandle.IsMetadataUpdating)
             {
                 _hasPendingQueuedRender = true;
 

src/Components/Components/src/HotReload/HotReloadManager.cs

@@ -11,7 +11,11 @@ namespace Microsoft.AspNetCore.Components.HotReload
 {
     internal static class HotReloadManager
     {
-       internal static event Action? OnDeltaApplied;
+        public static bool TestIsHotReloadSupported { get; set; }
+
+        public static bool IsHotReloadSupported => MetadataUpdater.IsSupported || TestIsHotReloadSupported;
+
+        internal static event Action? OnDeltaApplied;
 
         public static void DeltaApplied()
         {

src/Components/Components/src/Microsoft.AspNetCore.Components.csproj

@@ -13,7 +13,6 @@
   <ItemGroup>
     <Compile Include="$(ComponentsSharedSourceRoot)src\ArrayBuilder.cs" LinkBase="RenderTree" />
     <Compile Include="$(ComponentsSharedSourceRoot)src\JsonSerializerOptionsProvider.cs" />
-    <Compile Include="$(ComponentsSharedSourceRoot)src\HotReloadFeature.cs" LinkBase="HotReload" />
     <Compile Include="$(SharedSourceRoot)LinkerFlags.cs" LinkBase="Shared" />
     <Compile Include="$(SharedSourceRoot)QueryStringEnumerable.cs" LinkBase="Shared" />
   </ItemGroup>

src/Components/Components/src/Properties/AssemblyInfo.cs

@@ -1,3 +1,6 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
 using System.Runtime.CompilerServices;
 
 [assembly: InternalsVisibleTo("Microsoft.AspNetCore.Blazor.Build.Tests, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]

src/Components/Components/src/Properties/ILLink.Substitutions.xml

@@ -1,7 +1,7 @@
 <linker>
   <assembly fullname="Microsoft.AspNetCore.Components">
-    <type fullname="Microsoft.AspNetCore.Components.HotReload.HotReloadFeature" feature="System.Diagnostics.Debugger.IsSupported" featurevalue="false">
-      <method signature="System.Boolean get_IsSupported()" body="stub" value="false"  />
+    <type fullname="Microsoft.AspNetCore.Components.HotReload.HotReloadManager" feature="System.Reflection.Metadata.MetadataUpdater.IsSupported" featurevalue="false">
+      <method signature="System.Boolean get_IsHotReloadSupported()" body="stub" value="false"  />
     </type>
   </assembly>
 </linker>

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

@@ -40,7 +40,7 @@ Microsoft.AspNetCore.Components.NavigationOptions.ForceLoad.init -> void
 Microsoft.AspNetCore.Components.NavigationOptions.NavigationOptions() -> void
 Microsoft.AspNetCore.Components.NavigationOptions.ReplaceHistoryEntry.get -> bool
 Microsoft.AspNetCore.Components.NavigationOptions.ReplaceHistoryEntry.init -> void
-Microsoft.AspNetCore.Components.RenderHandle.IsHotReloading.get -> bool
+Microsoft.AspNetCore.Components.RenderHandle.IsMetadataUpdating.get -> bool
 Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder.Dispose() -> void
 Microsoft.AspNetCore.Components.Routing.Router.PreferExactMatches.get -> bool
 Microsoft.AspNetCore.Components.Routing.Router.PreferExactMatches.set -> void

src/Components/Components/src/RenderHandle.cs

@@ -47,7 +47,7 @@ public Dispatcher Dispatcher
         /// <summary>
         /// Gets a value that determines if the <see cref="Renderer"/> is triggering a render in response to a hot-reload change.
         /// </summary>
-        public bool IsHotReloading => HotReloadFeature.IsSupported && (_renderer?.IsHotReloading ?? false);
+        public bool IsMetadataUpdating => HotReloadManager.IsHotReloadSupported && (_renderer?.IsMetadataUpdating ?? false);
 
         /// <summary>
         /// Notifies the renderer that the component should be rendered.

src/Components/Components/src/RenderTree/RenderTreeDiffBuilder.cs

@@ -542,7 +542,7 @@ private static void UpdateRetainedChildComponent(
             var oldParameters = new ParameterView(ParameterViewLifetime.Unbound, oldTree, oldComponentIndex);
             var newParametersLifetime = new ParameterViewLifetime(diffContext.BatchBuilder);
             var newParameters = new ParameterView(newParametersLifetime, newTree, newComponentIndex);
-            if (!newParameters.DefinitelyEquals(oldParameters) || (HotReloadFeature.IsSupported && diffContext.Renderer.IsHotReloading))
+            if (!newParameters.DefinitelyEquals(oldParameters) || (HotReloadManager.IsHotReloadSupported && diffContext.Renderer.IsMetadataUpdating))
             {
                 componentState.SetDirectParameters(newParameters);
             }

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

@@ -97,7 +97,7 @@ public Renderer(IServiceProvider serviceProvider, ILoggerFactory loggerFactory,
             _logger = loggerFactory.CreateLogger<Renderer>();
             _componentFactory = new ComponentFactory(componentActivator);
 
-            if (HotReloadFeature.IsSupported)
+            if (HotReloadManager.IsHotReloadSupported)
             {
                 HotReloadManager.OnDeltaApplied += RenderRootComponentsOnHotReload;
             }
@@ -121,9 +121,9 @@ private static IComponentActivator GetComponentActivatorOrDefault(IServiceProvid
         protected internal ElementReferenceContext? ElementReferenceContext { get; protected set; }
 
         /// <summary>
-        /// Gets a value that determines if the <see cref="Renderer"/> is triggering a render in response to a hot-reload change.
+        /// Gets a value that determines if the <see cref="Renderer"/> is triggering a render in response to a (metadata update) hot-reload change.
         /// </summary>
-        internal bool IsHotReloading { get; private set; }
+        internal bool IsMetadataUpdating { get; private set; }
 
         private async void RenderRootComponentsOnHotReload()
         {
@@ -139,7 +139,7 @@ await Dispatcher.InvokeAsync(() =>
                     return;
                 }
 
-                IsHotReloading = true;
+                IsMetadataUpdating = true;
                 try
                 {
                     foreach (var (componentState, initialParameters) in _rootComponents)
@@ -149,7 +149,7 @@ await Dispatcher.InvokeAsync(() =>
                 }
                 finally
                 {
-                    IsHotReloading = false;
+                    IsMetadataUpdating = false;
                 }
             });
         }
@@ -227,7 +227,7 @@ protected async Task RenderRootComponentAsync(int componentId, ParameterView ini
             // During the asynchronous rendering process we want to wait up until all components have
             // finished rendering so that we can produce the complete output.
             var componentState = GetRequiredComponentState(componentId);
-            if (HotReloadFeature.IsSupported)
+            if (HotReloadManager.IsHotReloadSupported)
             {
                 // when we're doing hot-reload, stash away the parameters used while rendering root components.
                 // We'll use this to trigger re-renders on hot reload updates.
@@ -998,7 +998,7 @@ public void Dispose()
         /// <inheritdoc />
         public async ValueTask DisposeAsync()
         {
-            if (HotReloadFeature.IsSupported)
+            if (HotReloadManager.IsHotReloadSupported)
             {
                 HotReloadManager.OnDeltaApplied -= RenderRootComponentsOnHotReload;
             }

src/Components/Components/src/Routing/Router.cs

@@ -6,6 +6,7 @@
 using System;
 using System.Collections.Generic;
 using System.Reflection;
+using System.Reflection.Metadata;
 using System.Runtime.ExceptionServices;
 using System.Threading;
 using System.Threading.Tasks;
@@ -99,7 +100,7 @@ public void Attach(RenderHandle renderHandle)
             _locationAbsolute = NavigationManager.Uri;
             NavigationManager.LocationChanged += OnLocationChanged;
 
-            if  (HotReloadFeature.IsSupported)
+            if (MetadataUpdater.IsSupported)
             {
                 HotReloadManager.OnDeltaApplied += ClearRouteCaches;
             }
@@ -143,7 +144,7 @@ public async Task SetParametersAsync(ParameterView parameters)
         public void Dispose()
         {
             NavigationManager.LocationChanged -= OnLocationChanged;
-            if (HotReloadFeature.IsSupported)
+            if (MetadataUpdater.IsSupported)
             {
                 HotReloadManager.OnDeltaApplied -= ClearRouteCaches;
             }