Cherry pick extensions fix (#39306)

Author: 333fred

src/RazorSdk/Tool/DiscoverCommand.cs

@@ -96,9 +96,6 @@ protected override bool ValidateArguments()
 
         private const string RazorCompilerFileName = "Microsoft.CodeAnalysis.Razor.Compiler.dll";
 
-        internal static string GetRazorCompilerPath()
-            => Path.Combine(Path.GetDirectoryName(typeof(Application).Assembly.Location), RazorCompilerFileName);
-
         /// <summary>
         /// Replaces the assembly for MVC extension with the one shipped alongside SDK (as opposed to the one from NuGet).
         /// </summary>
@@ -144,16 +141,8 @@ protected override Task<int> ExecuteCoreAsync()
                 return Task.FromResult(ExitCodeFailure);
             }
 
-            // Loading all of the extensions should succeed as the dependency checker will have already
-            // loaded them.
-            var extensions = new RazorExtension[ExtensionNames.Values.Count];
-            for (var i = 0; i < ExtensionNames.Values.Count; i++)
-            {
-                extensions[i] = new AssemblyExtension(ExtensionNames.Values[i], Parent.Loader.LoadFromPath(ExtensionFilePaths.Values[i]));
-            }
-
             var version = RazorLanguageVersion.Parse(Version.Value());
-            var configuration = RazorConfiguration.Create(version, Configuration.Value(), extensions);
+            var configuration = new RazorConfiguration(version, Configuration.Value(), Extensions: []);
 
             var result = ExecuteCore(
                 configuration: configuration,
@@ -176,6 +165,8 @@ private int ExecuteCore(RazorConfiguration configuration, string projectDirector
 
             var engine = RazorProjectEngine.Create(configuration, RazorProjectFileSystem.Empty, b =>
             {
+                b.RegisterExtensions();
+
                 b.Features.Add(new DefaultMetadataReferenceFeature() { References = metadataReferences });
                 b.Features.Add(new CompilationTagHelperFeature());
                 b.Features.Add(new DefaultTagHelperDescriptorProvider());

src/RazorSdk/Tool/GenerateCommand.cs

@@ -74,25 +74,8 @@ protected override Task<int> ExecuteCoreAsync()
                 return Task.FromResult(ExitCodeFailure);
             }
 
-            // Loading all of the extensions should succeed as the dependency checker will have already
-            // loaded them.
-            var extensions = new RazorExtension[ExtensionNames.Values.Count];
-            string razorCompilerPath = null;
-            for (var i = 0; i < ExtensionNames.Values.Count; i++)
-            {
-                // If the extension is the Razor compiler, we'll use the referenced assembly (instead of the SDK one).
-                // Otherwise the extension's ProvideRazorExtensionInitializerAttribute would be different from the AssemblyExtension's one,
-                // hence the extension would not be loaded properly.
-                razorCompilerPath ??= DiscoverCommand.GetRazorCompilerPath();
-                var assembly = string.Equals(ExtensionFilePaths.Values[i], razorCompilerPath, StringComparison.OrdinalIgnoreCase)
-                    ? typeof(AssemblyExtension).Assembly
-                    : Parent.Loader.LoadFromPath(ExtensionFilePaths.Values[i]);
-
-                extensions[i] = new AssemblyExtension(ExtensionNames.Values[i], assembly);
-            }
-
             var version = RazorLanguageVersion.Parse(Version.Value());
-            var configuration = RazorConfiguration.Create(version, Configuration.Value(), extensions);
+            var configuration = new RazorConfiguration(version, Configuration.Value(), Extensions: []);
 
             var sourceItems = GetSourceItems(
                 Sources.Values, Outputs.Values, RelativePaths.Values,
@@ -203,6 +186,8 @@ private int ExecuteCore(
 
             var engine = RazorProjectEngine.Create(configuration, compositeFileSystem, b =>
             {
+                b.RegisterExtensions();
+
                 b.Features.Add(new StaticTagHelperFeature() { TagHelpers = tagHelpers, });
                 b.Features.Add(new DefaultTypeNameFeature());