fix nullability of AssemblyEnumerator.GetTypes

src/Adapter/MSTest.TestAdapter/Discovery/AssemblyEnumerator.cs

@@ -73,7 +73,7 @@
 
         Assembly assembly = PlatformServiceProvider.Instance.FileOperations.LoadAssembly(assemblyFileName, isReflectionOnly: false);
 
-        Type[] types = GetTypes(assembly, assemblyFileName, warnings);
+        Type?[] types = GetTypes(assembly, assemblyFileName, warnings);
         bool discoverInternals = ReflectHelper.GetDiscoverInternalsAttribute(assembly) != null;
         TestIdGenerationStrategy testIdGenerationStrategy = ReflectHelper.GetTestIdGenerationStrategy(assembly);
 
@@ -103,7 +103,7 @@
             },
         };
 
-        foreach (Type type in types)
+        foreach (Type? type in types)
         {
             if (type == null)
             {
@@ -125,7 +125,7 @@
     /// <param name="assemblyFileName">The file name of the assembly.</param>
     /// <param name="warningMessages">Contains warnings if any, that need to be passed back to the caller.</param>
     /// <returns>Gets the types defined in the provided assembly.</returns>
-    internal static Type[] GetTypes(Assembly assembly, string assemblyFileName, ICollection<string>? warningMessages)
+    internal static Type?[] GetTypes(Assembly assembly, string assemblyFileName, ICollection<string>? warningMessages)
     {
         try
         {
@@ -136,14 +136,14 @@
             PlatformServiceProvider.Instance.AdapterTraceLogger.LogWarning($"MSTestExecutor.TryGetTests: {Resource.TestAssembly_AssemblyDiscoveryFailure}", assemblyFileName, ex);
             PlatformServiceProvider.Instance.AdapterTraceLogger.LogWarning(Resource.ExceptionsThrown);
 
-            if (ex.LoaderExceptions != null)
+            if (ex.LoaderExceptions.Any())
             {
                 // If not able to load all type, log a warning and continue with loaded types.
                 string message = string.Format(CultureInfo.CurrentCulture, Resource.TypeLoadFailed, assemblyFileName, GetLoadExceptionDetails(ex));
 
                 warningMessages?.Add(message);
 
                 foreach (Exception? loaderEx in ex.LoaderExceptions)
                 {
                     PlatformServiceProvider.Instance.AdapterTraceLogger.LogWarning("{0}", loaderEx);
                 }

src/Adapter/MSTest.TestAdapter/Execution/TypeCache.cs

@@ -384,14 +384,19 @@ private TestAssemblyInfo GetAssemblyInfo(Assembly assembly)
             {
                 var assemblyInfo = new TestAssemblyInfo(assembly);
 
-                Type[] types = AssemblyEnumerator.GetTypes(assembly, assembly.FullName!, null);
+                Type?[] types = AssemblyEnumerator.GetTypes(assembly, assembly.FullName!, null);
 
-                foreach (Type t in types)
+                foreach (Type? type in types)
                 {
+                    if (type == null)
+                    {
+                        continue;
+                    }
+
                     try
                     {
                         // Only examine classes which are TestClass or derives from TestClass attribute
-                        if (!@this._reflectionHelper.IsDerivedAttributeDefined<TestClassAttribute>(t, inherit: false))
+                        if (!@this._reflectionHelper.IsDerivedAttributeDefined<TestClassAttribute>(type, inherit: false))
                         {
                             continue;
                         }
@@ -401,14 +406,14 @@ private TestAssemblyInfo GetAssemblyInfo(Assembly assembly)
                         // If we fail to discover type from an assembly, then do not abort. Pick the next type.
                         PlatformServiceProvider.Instance.AdapterTraceLogger.LogWarning(
                             "TypeCache: Exception occurred while checking whether type {0} is a test class or not. {1}",
-                            t.FullName,
+                            type.FullName,
                             ex);
 
                         continue;
                     }
 
                     // Enumerate through all methods and identify the Assembly Init and cleanup methods.
-                    foreach (MethodInfo methodInfo in PlatformServiceProvider.Instance.ReflectionOperations.GetDeclaredMethods(t))
+                    foreach (MethodInfo methodInfo in PlatformServiceProvider.Instance.ReflectionOperations.GetDeclaredMethods(type))
                     {
                         if (@this.IsAssemblyOrClassInitializeMethod<AssemblyInitializeAttribute>(methodInfo))
                         {

test/UnitTests/MSTestAdapter.UnitTests/Discovery/AssemblyEnumeratorTests.cs

@@ -94,7 +94,7 @@ public void GetTypesShouldReturnSetOfDefinedTypes()
         // Setup mocks
         mockAssembly.Setup(a => a.GetTypes()).Returns(expectedTypes);
 
-        IReadOnlyList<Type> types = AssemblyEnumerator.GetTypes(mockAssembly.Object, string.Empty, _warnings);
+        IReadOnlyList<Type?> types = AssemblyEnumerator.GetTypes(mockAssembly.Object, string.Empty, _warnings);
         Verify(expectedTypes.SequenceEqual(types));
     }
 
@@ -116,7 +116,7 @@ public void GetTypesShouldReturnReflectionTypeLoadExceptionTypesOnException()
         // Setup mocks
         mockAssembly.Setup(a => a.GetTypes()).Throws(new ReflectionTypeLoadException(reflectedTypes, null));
 
-        IReadOnlyList<Type> types = AssemblyEnumerator.GetTypes(mockAssembly.Object, string.Empty, _warnings);
+        IReadOnlyList<Type?> types = AssemblyEnumerator.GetTypes(mockAssembly.Object, string.Empty, _warnings);
 
         Verify(types is not null);
         Verify(reflectedTypes.Equals(types));
@@ -131,7 +131,7 @@ public void GetTypesShouldLogWarningsWhenReflectionFailsWithLoaderExceptions()
         mockAssembly.Setup(a => a.GetTypes()).Throws(new ReflectionTypeLoadException(null, exceptions));
         mockAssembly.Setup(a => a.GetTypes()).Throws(new ReflectionTypeLoadException(null, exceptions));
 
-        IReadOnlyList<Type> types = AssemblyEnumerator.GetTypes(mockAssembly.Object, "DummyAssembly", _warnings);
+        IReadOnlyList<Type?> types = AssemblyEnumerator.GetTypes(mockAssembly.Object, "DummyAssembly", _warnings);
 
         Verify(_warnings.Count == 1);
         Verify(_warnings.ToList().Contains(