Razor EA: load from ServiceHubCore (#77720)

* Razor EA: load from ServiceHubCore

* Update src/Tools/ExternalAccess/Razor/RazorAnalyzerAssemblyResolver.cs

Co-authored-by: Jan Jones <[email protected]>

* Trim trailing slashes

* Update src/Tools/ExternalAccess/Razor/RazorAnalyzerAssemblyResolver.cs

Co-authored-by: Jan Jones <[email protected]>

* Fix trim call

* PR feedback

---------

Co-authored-by: Jan Jones <[email protected]>
Co-authored-by: Jared Parsons <[email protected]>

Author: 3 people

src/Tools/ExternalAccess/Razor/EditorFeatures/RazorAnalyzerAssemblyResolver.cs

@@ -25,6 +25,8 @@ internal sealed class RazorAnalyzerAssemblyResolver() : IAnalyzerAssemblyResolve
         public const string RazorUtilsAssemblyName = "Microsoft.AspNetCore.Razor.Utilities.Shared";
         public const string ObjectPoolAssemblyName = "Microsoft.Extensions.ObjectPool";
 
+        internal const string ServiceHubCoreFolderName = "ServiceHubCore";
+
         internal static readonly ImmutableArray<string> RazorAssemblyNames = [RazorCompilerAssemblyName, RazorUtilsAssemblyName, ObjectPoolAssemblyName];
 
         public Assembly? Resolve(AnalyzerAssemblyLoader loader, AssemblyName assemblyName, AssemblyLoadContext directoryContext, string directory) =>
@@ -54,6 +56,16 @@ internal sealed class RazorAnalyzerAssemblyResolver() : IAnalyzerAssemblyResolve
             }
 
             var assemblyFileName = $"{assemblyName.Name}.dll";
+
+            // Depending on who wins the race to load these assemblies, the base directory will either be the tooling root (if Roslyn wins)
+            // or the ServiceHubCore subfolder (razor). In the root directory these are netstandard2.0 targeted, in ServiceHubCore they are 
+            // .net targeted. We need to always pick the same set of assemblies regardless of who causes us to load. Because this code only
+            // runs in a .net based host, it's safe to always choose the .net targeted ServiceHubCore versions.
+            if (!Path.GetFileName(directory.AsSpan().TrimEnd(Path.DirectorySeparatorChar)).Equals(ServiceHubCoreFolderName, StringComparison.OrdinalIgnoreCase))
+            {
+                directory = Path.Combine(directory, ServiceHubCoreFolderName);
+            }
+
             var assemblyPath = Path.Combine(directory, assemblyFileName);
             if (File.Exists(assemblyPath))
             {

src/Tools/ExternalAccess/RazorTest/RazorAnalyzerAssemblyResolverTests.cs

@@ -40,6 +40,7 @@ public void Dispose()
 
     private void CreateRazorAssemblies(string directory, string versionNumber = "1.0.0.0")
     {
+        _ = Directory.CreateDirectory(directory);
         foreach (var simpleName in RazorAnalyzerAssemblyResolver.RazorAssemblyNames)
         {
             BuildOne(simpleName);
@@ -149,5 +150,40 @@ public void FirstLoadWins()
             Assert.Same(assembly1, assembly2);
         });
     }
+
+    [Fact]
+    public void ChooseServiceHubFolder()
+    {
+        var dir = TempRoot.CreateDirectory().Path;
+        CreateRazorAssemblies(dir);
+        var serviceHubFolder = Path.Combine(dir, RazorAnalyzerAssemblyResolver.ServiceHubCoreFolderName);
+        CreateRazorAssemblies(serviceHubFolder);
+
+        coreTest(dir, serviceHubFolder);
+        coreTest(dir + Path.DirectorySeparatorChar, serviceHubFolder);
+        coreTest(serviceHubFolder, serviceHubFolder);
+        coreTest(serviceHubFolder + Path.DirectorySeparatorChar, serviceHubFolder);
+
+        void coreTest(string loadDir, string serviceHubDir)
+        {
+            var name = Path.GetFileName(loadDir.AsSpan());
+            RunWithLoader((resolver, loader, currentLoadContext) =>
+            {
+                var assembly1 = resolver.Resolve(
+                    loader,
+                    new AssemblyName(RazorAnalyzerAssemblyResolver.RazorCompilerAssemblyName),
+                    currentLoadContext,
+                    loadDir);
+                var assembly2 = resolver.Resolve(
+                    loader,
+                    new AssemblyName(RazorAnalyzerAssemblyResolver.RazorCompilerAssemblyName),
+                    currentLoadContext,
+                    serviceHubFolder);
+                Assert.NotNull(assembly1);
+                Assert.Same(assembly1, assembly2);
+                Assert.Equal(serviceHubFolder, Path.GetDirectoryName(assembly1.Location));
+            });
+        }
+    }
 }
 #endif