Allow clearing CPU selection without selection payload

Author: PrimeBuild-pc

Platforms/Windows/IProcessCpuSetHandler.cs

@@ -48,10 +48,10 @@ public interface IProcessCpuSetHandler : IDisposable
         /// <summary>
         /// Applies a topology-aware CPU selection to the process using CPU Sets.
         /// </summary>
-        /// <param name="selection">The CPU selection to apply.</param>
+        /// <param name="selection">The CPU selection to apply. Ignored and allowed to be null when <paramref name="clearSelection"/> is true.</param>
         /// <param name="clearSelection">If true, clears the CPU Set selection and ignores <paramref name="selection"/>.</param>
         /// <returns>True if the operation succeeded, false otherwise.</returns>
-        bool ApplyCpuSelection(CpuSelection selection, bool clearSelection = false);
+        bool ApplyCpuSelection(CpuSelection? selection, bool clearSelection = false);
 
         /// <summary>
         /// Gets the average CPU usage for this process.

Platforms/Windows/ProcessCpuSetHandler.cs

@@ -231,10 +231,8 @@ public bool ApplyCpuSetMask(long affinityMask, bool clearMask = false)
             return false;
         }
 
-        public bool ApplyCpuSelection(CpuSelection selection, bool clearSelection = false)
+        public bool ApplyCpuSelection(CpuSelection? selection, bool clearSelection = false)
         {
-            ArgumentNullException.ThrowIfNull(selection);
-
             if (this.disposed)
             {
                 throw new ObjectDisposedException(nameof(ProcessCpuSetHandler));
@@ -250,6 +248,8 @@ public bool ApplyCpuSelection(CpuSelection selection, bool clearSelection = fals
                 return this.ApplyCpuSetIds(null, 0, "clear CPU Set selection");
             }
 
+            ArgumentNullException.ThrowIfNull(selection);
+
             var cpuSetIds = this.cpuSetMapping.ResolveCpuSetIds(selection);
             if (cpuSetIds.Count == 0)
             {
@@ -393,4 +393,3 @@ private class CpuTimeTimestamp
         }
     }
 }
-

Tests/ThreadPilot.Core.Tests/ProcessCpuSetHandlerTests.cs

@@ -116,6 +116,29 @@ public void ProcessCpuSetHandler_ApplyCpuSelection_WithClearSelection_ClearsCpuS
             Assert.Equal(0U, nativeApi.LastAppliedCpuSetCount);
         }
 
+        [Fact]
+        public void ProcessCpuSetHandler_ApplyCpuSelection_WithClearSelectionAndNullSelection_ClearsCpuSets()
+        {
+            var nativeApi = new FakeProcessCpuSetNativeApi();
+            using var handler = CreateHandler(nativeApi, CpuSetMapping.Empty);
+
+            var result = handler.ApplyCpuSelection(null!, clearSelection: true);
+
+            Assert.True(result);
+            Assert.Null(nativeApi.LastAppliedCpuSetIds);
+            Assert.Equal(0U, nativeApi.LastAppliedCpuSetCount);
+        }
+
+        [Fact]
+        public void ProcessCpuSetHandler_ApplyCpuSelection_WithNullSelectionAndClearFalse_ThrowsArgumentNullException()
+        {
+            var nativeApi = new FakeProcessCpuSetNativeApi();
+            using var handler = CreateHandler(nativeApi, CpuSetMapping.Empty);
+
+            Assert.Throws<ArgumentNullException>(() =>
+                handler.ApplyCpuSelection(null!, clearSelection: false));
+        }
+
         [Fact]
         public void ProcessCpuSetHandler_ApplyCpuSelection_WithExplicitCpuSetIds_AppliesThoseIds()
         {