Imported Upstream version 6.0.0.172

Former-commit-id: f3cc9b82f3e5bd8f0fd3ebc098f789556b44e9cd

external/corefx/src/System.IO.Ports/tests/SerialPort/GetPortNames.cs

@@ -19,7 +19,7 @@ namespace System.IO.Ports.Tests
         /// <summary>
         /// Check that all ports either open correctly or fail with UnauthorizedAccessException (which implies they're already open)
         /// </summary>
-        [Fact]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotWindowsNanoServer))]
         private void OpenEveryPortName()
         {
             foreach (string portName in SerialPort.GetPortNames())
@@ -40,7 +40,7 @@ namespace System.IO.Ports.Tests
         /// Test that SerialPort.GetPortNames finds every port that the test helpers have found. 
         /// (On Windows, the latter uses a different technique to SerialPort to find ports).
         /// </summary>
-        [Fact]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotWindowsNanoServer))]
         private void AllHelperPortsAreInGetPortNames()
         {
             string[] serialPortNames = SerialPort.GetPortNames();
@@ -55,7 +55,7 @@ namespace System.IO.Ports.Tests
         /// Test that the test helpers have found every port that SerialPort.GetPortNames has found
         /// This catches regressions in the test helpers, eg GH #18928 / #20668
         /// </summary>
-        [Fact]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotWindowsNanoServer))]
         private void AllGetPortNamesAreInHelperPorts()
         {
             string[] helperPortNames = PortHelper.GetPorts();

external/corefx/src/System.IO.Ports/tests/SerialPort/OpenDevices.cs

@@ -12,7 +12,7 @@ namespace System.IO.Ports.Tests
 {
     public class OpenDevices : PortsTest
     {
-        [Fact]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotWindowsNanoServer))] // ActiveIssue: https://github.com/dotnet/corefx/issues/29756
         [ActiveIssue("https://github.com/dotnet/corefx/issues/23294", TargetFrameworkMonikers.Uap)]
         public void OpenDevices01()
         {

external/corefx/src/System.IO.Ports/tests/Support/TCSupport.cs

@@ -32,6 +32,12 @@ namespace Legacy.Support
 
         private static void InitializeSerialInfo()
         {
+            if (PlatformDetection.IsWindowsNanoServer)
+            {
+                s_localMachineSerialPortRequirements = SerialPortRequirements.None;
+                return;
+            }
+
             GenerateSerialInfo();
 
             if (s_localMachineSerialInfo.LoopbackPortName != null)