Fix NullReferenceException when the native enumerator returns null

src/Orc.SystemInfo.Tests/Orc.SystemInfo.Tests.csproj

@@ -18,6 +18,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.2" />
+    <PackageReference Include="Moq" Version="4.20.69" />
     <PackageReference Include="NUnit" Version="3.13.3" PrivateAssets="all" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" PrivateAssets="all" />
     <PackageReference Include="PublicApiGenerator" Version="11.0.0" PrivateAssets="all" />

src/Orc.SystemInfo.Tests/Wmi/WindowsManagementObjectEnumeratorFacts.cs

@@ -0,0 +1,40 @@
+namespace Orc.SystemInfo.Tests
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Text;
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Moq;
+    using NUnit.Framework;
+    using Orc.SystemInfo.Win32;
+    using Orc.SystemInfo.Wmi;
+
+    public class WindowsManagementObjectEnumeratorFacts
+    {
+        [Test]
+        public async Task Returns_False_When_Enumerator_Returns_Null_Async()
+        {
+            IWbemClassObject objects;
+            uint returnedCount;
+
+            var wbemClassObjectEnumeratorMock = new Mock<IWbemClassObjectEnumerator>();
+
+            wbemClassObjectEnumeratorMock.Setup(x => x.Next(It.IsAny<int>(), It.IsAny<uint>(), out objects, out returnedCount))
+                .Returns((int to, uint c, out IWbemClassObject o, out uint rc) =>
+                {
+                    o = null;
+                    rc = 0;
+
+                    return new HResult(0);
+                });
+
+            using var enumerator = new WindowsManagementObjectEnumerator(wbemClassObjectEnumeratorMock.Object);
+
+            var moveNextResult = enumerator.MoveNext();
+
+            Assert.That(moveNextResult, Is.False);
+        }
+    }
+}

src/Orc.SystemInfo/Properties/AssemblyInfo.cs

@@ -17,3 +17,4 @@
 [assembly: ComVisible(false)]
 
 [assembly: InternalsVisibleTo("Orc.SystemInfo.Tests")]
+[assembly: InternalsVisibleTo("DynamicProxyGenAssembly2")]

src/Orc.SystemInfo/Win32/HResult.cs

@@ -94,4 +94,9 @@ public void ThrowIfFailed()
             throw ex;
         }
     }
-}
+
+    public override string ToString()
+    {
+        return $"{_value} (Failed = {Failed})";
+    }
+}

src/Orc.SystemInfo/Win32/Wbem/Extensions/IWbemClassObjectEnumeratorExtensions.cs

@@ -1,11 +1,10 @@
 namespace Orc.SystemInfo.Win32;
 
-using System;
 using System.Threading;
 
 public static class IWbemClassObjectEnumeratorExtensions
 {
-    internal static IWbemClassObject Next(this IWbemClassObjectEnumerator wbemClassObjectEnumerator)
+    internal static IWbemClassObject? Next(this IWbemClassObjectEnumerator wbemClassObjectEnumerator)
     {
         const uint count = 1;
         var hresult = wbemClassObjectEnumerator.Next(Timeout.Infinite, count, out var current, out _);

src/Orc.SystemInfo/Wmi/WindowsManagementObjectEnumerator.cs

@@ -42,10 +42,15 @@ public bool MoveNext()
         ThrowIfDisposed();
 
         var currentWmiObject = _wbemClassObjectEnumerator.Next();
+        if (currentWmiObject is null)
+        {
+            return false;
+        }
 
 #pragma warning disable IDISP003 // Dispose previous before re-assigning
         Current = new WindowsManagementObject(currentWmiObject);
 #pragma warning restore IDISP003 // Dispose previous before re-assigning
+
         return true;
     }
 
@@ -70,7 +75,10 @@ public void Dispose()
             return;
         }
 
-        Marshal.ReleaseComObject(_wbemClassObjectEnumerator);
+        if (Marshal.IsComObject(_wbemClassObjectEnumerator))
+        {
+            Marshal.ReleaseComObject(_wbemClassObjectEnumerator);
+        }
 
         _disposed = true;
     }