From e6dc77cb079a77ca62c00f9e96b063c6d7854b24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Amaury=20Lev=C3=A9?= <amauryleve@microsoft.com>
Date: Sun, 5 Jul 2026 15:18:50 +0200
Subject: [PATCH] Reimplement the source assembly-reference check without
 ObjectModel (Phase 6e-4c2)

TestSourceHandler.IsAssemblyReferenced (netfx) used
AssemblyHelper.DoesReferencesAssembly from
Microsoft.VisualStudio.TestPlatform.ObjectModel.Utilities to decide whether a
source assembly references the test framework before running discovery.

Replace that call with a local neutral DoesSourceReferenceAssembly helper that
reproduces the exact observable behavior of the VSTest implementation:

- ReflectionOnlyLoadFrom(source), then GetReferencedAssemblies().
- Match a referenced assembly by simple name (OrdinalIgnoreCase) plus public
  key token bytes; version is ignored -- identical to
  AssemblyLoadWorker.CheckAssemblyReference.
- Null/empty source or null reference assembly returns null (undeterminable).
- Any exception returns null so discovery proceeds conservatively.

Fidelity note: the VSTest DoesReferencesAssembly created a child AppDomain and an
AssemblyLoadWorker instance, but then called the *static*
AssemblyLoadWorker.CheckAssemblyReference -- the worker instance is never used and
the ReflectionOnlyLoadFrom actually runs in the current domain. The child domain
is therefore dead code for the result, so omitting it is behavior-preserving for
every input where AppDomain creation would have succeeded.

Removes the last real ObjectModel dependency from TestSourceHandler.

Verified: PlatformServices.UnitTests 935 (net462) / 897 (net8.0);
DesktopTestSourceTests IsAssemblyReferenced branches 7/7 (referenced,
not-referenced, null-name, null-source); PlatformServices.Desktop.IntegrationTests
15/15. All real TFMs build 0-warning.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
---
 .../Services/TestSourceHandler.cs             | 72 +++++++++++++++++--
 1 file changed, 68 insertions(+), 4 deletions(-)

diff --git a/src/Adapter/MSTestAdapter.PlatformServices/Services/TestSourceHandler.cs b/src/Adapter/MSTestAdapter.PlatformServices/Services/TestSourceHandler.cs
index 4255641119..a2ce548535 100644
--- a/src/Adapter/MSTestAdapter.PlatformServices/Services/TestSourceHandler.cs
+++ b/src/Adapter/MSTestAdapter.PlatformServices/Services/TestSourceHandler.cs
@@ -5,9 +5,6 @@
 using Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices.AppContainer;
 #endif
 using Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices.Interface;
-#if NETFRAMEWORK
-using Microsoft.VisualStudio.TestPlatform.ObjectModel.Utilities;
-#endif
 
 namespace Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices;
 
@@ -79,7 +76,7 @@ public bool IsAssemblyReferenced(AssemblyName assemblyName, string source)
     {
 #if NETFRAMEWORK
         // This loads the dll in a different app domain. We can optimize this to load in the current domain since this code could be run in a new app domain anyway.
-        bool? utfReference = AssemblyHelper.DoesReferencesAssembly(source, assemblyName);
+        bool? utfReference = DoesSourceReferenceAssembly(source, assemblyName);
 
         // If no reference to UTF don't run discovery. Take conservative approach. If not able to find proceed with discovery.
         return !utfReference.HasValue || utfReference.Value;
@@ -94,6 +91,73 @@ public bool IsAssemblyReferenced(AssemblyName assemblyName, string source)
 #endif
     }
 
+#if NETFRAMEWORK
+    /// <summary>
+    /// Checks whether the source assembly directly references the given assembly.
+    /// Only the assembly simple name and public key token are matched; version is ignored.
+    /// Returns <see langword="null"/> if the reference could not be determined.
+    /// </summary>
+    /// <param name="source"> The path to the source assembly to inspect. </param>
+    /// <param name="referenceAssembly"> The assembly to look for in the source's references. </param>
+    /// <returns> <see langword="true"/> if referenced, <see langword="false"/> if not, <see langword="null"/> if undeterminable. </returns>
+    private static bool? DoesSourceReferenceAssembly(string source, AssemblyName referenceAssembly)
+    {
+        if (string.IsNullOrEmpty(source) || referenceAssembly is null)
+        {
+            return null;
+        }
+
+        try
+        {
+            string? referenceAssemblyName = referenceAssembly.Name;
+            byte[] referenceAssemblyPublicKeyToken = referenceAssembly.GetPublicKeyToken();
+
+            // ReflectionOnlyLoadFrom loads from the specified path only (no probing) and does not
+            // execute any code from the loaded assembly.
+            var assembly = Assembly.ReflectionOnlyLoadFrom(source);
+
+            foreach (AssemblyName referencedAssembly in assembly.GetReferencedAssemblies())
+            {
+                // Match without version: only the simple name and public key token.
+                if (!string.Equals(referencedAssembly.Name, referenceAssemblyName, StringComparison.OrdinalIgnoreCase))
+                {
+                    continue;
+                }
+
+                if (ArePublicKeyTokensEqual(referencedAssembly.GetPublicKeyToken(), referenceAssemblyPublicKeyToken))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+        catch
+        {
+            // Return null if we are not able to check.
+            return null;
+        }
+    }
+
+    private static bool ArePublicKeyTokensEqual(byte[] left, byte[] right)
+    {
+        if (left.Length != right.Length)
+        {
+            return false;
+        }
+
+        for (int i = 0; i < left.Length; ++i)
+        {
+            if (left[i] != right[i])
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+#endif
+
     /// <summary>
     /// Gets the set of sources (dll's/exe's) that contain tests. If a source is a package (appx), return the file (dll/exe) that contains tests from it.
     /// </summary>