Re-enable Windows test that verifies DriveInfo.VolumeLabel setter fails on SUBST'd drive

src/libraries/Common/tests/System/IO/VirtualDriveHelper.Windows.cs

@@ -0,0 +1,148 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Runtime.Versioning;
+
+namespace System.IO
+{
+    // Adds test helper APIs to manipulate Windows virtual drives via SUBST.
+    [SupportedOSPlatform("windows")]
+    public class VirtualDriveHelper : IDisposable
+    {
+        // Temporary Windows directory that can be mounted to a drive letter using the subst command
+        private string? _virtualDriveTargetDir = null;
+        // Windows drive letter that points to a mounted directory using the subst command
+        private char _virtualDriveLetter = default;
+
+        /// <summary>
+        /// If there is a SUBST'ed drive, Dispose unmounts it to free the drive letter.
+        /// </summary>
+        public void Dispose()
+        {
+            try
+            {
+                if (VirtualDriveLetter != default)
+                {
+                    DeleteVirtualDrive(VirtualDriveLetter);
+                    Directory.Delete(VirtualDriveTargetDir, recursive: true);
+                }
+            }
+            catch { } // avoid exceptions on dispose
+        }
+
+        /// <summary>
+        /// Returns the path of a folder that is to be mounted using SUBST.
+        /// </summary>
+        public string VirtualDriveTargetDir
+        {
+            get
+            {
+                if (_virtualDriveTargetDir == null)
+                {
+                    // Create a folder inside the temp directory so that it can be mounted to a drive letter with subst
+                    _virtualDriveTargetDir = Path.Join(Path.GetTempPath(), Path.GetRandomFileName());
+                    Directory.CreateDirectory(_virtualDriveTargetDir);
+                }
+
+                return _virtualDriveTargetDir;
+            }
+        }
+
+        /// <summary>
+        /// Returns the drive letter of a drive letter that represents a mounted folder using SUBST.
+        /// </summary>
+        public char VirtualDriveLetter
+        {
+            get
+            {
+                if (_virtualDriveLetter == default)
+                {
+                    // Mount the folder to a drive letter
+                    _virtualDriveLetter = CreateVirtualDrive(VirtualDriveTargetDir);
+                }
+                return _virtualDriveLetter;
+            }
+        }
+
+        ///<summary>
+        /// On Windows, mounts a folder to an assigned virtual drive letter using the subst command.
+        /// subst is not available in Windows Nano.
+        /// </summary>
+        private static char CreateVirtualDrive(string targetDir)
+        {
+            char driveLetter = GetNextAvailableDriveLetter();
+            bool success = RunProcess(CreateProcessStartInfo("cmd", "/c", SubstPath, $"{driveLetter}:", targetDir));
+            if (!success || !DriveInfo.GetDrives().Any(x => x.Name[0] == driveLetter))
+            {
+                throw new InvalidOperationException($"Could not create virtual drive {driveLetter}: with subst");
+            }
+            return driveLetter;
+
+            // Finds the next unused drive letter and returns it.
+            char GetNextAvailableDriveLetter()
+            {
+                List<char> existingDrives = DriveInfo.GetDrives().Select(x => x.Name[0]).ToList();
+
+                // A,B are reserved, C is usually reserved
+                IEnumerable<int> range = Enumerable.Range('D', 'Z' - 'D');
+                IEnumerable<char> castRange = range.Select(x => Convert.ToChar(x));
+                IEnumerable<char> allDrivesLetters = castRange.Except(existingDrives);
+
+                if (!allDrivesLetters.Any())
+                {
+                    throw new ArgumentOutOfRangeException("No drive letters available");
+                }
+
+                return allDrivesLetters.First();
+            }
+        }
+
+        /// <summary>
+        /// On Windows, unassigns the specified virtual drive letter from its mounted folder.
+        /// </summary>
+        private static void DeleteVirtualDrive(char driveLetter)
+        {
+            bool success = RunProcess(CreateProcessStartInfo("cmd", "/c", SubstPath, "/d", $"{driveLetter}:"));
+            if (!success || DriveInfo.GetDrives().Any(x => x.Name[0] == driveLetter))
+            {
+                throw new InvalidOperationException($"Could not delete virtual drive {driveLetter}: with subst");
+            }
+        }
+
+        private static ProcessStartInfo CreateProcessStartInfo(string fileName, params string[] arguments)
+        {
+            var info = new ProcessStartInfo
+            {
+                FileName = fileName,
+                UseShellExecute = false,
+                RedirectStandardOutput = true
+            };
+
+            foreach (var argument in arguments)
+            {
+                info.ArgumentList.Add(argument);
+            }
+
+            return info;
+        }
+
+        private static bool RunProcess(ProcessStartInfo startInfo)
+        {
+            using var process = Process.Start(startInfo);
+            process.WaitForExit();
+            return process.ExitCode == 0;
+        }
+
+        private static string SubstPath
+        {
+            get
+            {
+                string systemRoot = Environment.GetEnvironmentVariable("SystemRoot") ?? @"C:\Windows";
+                return Path.Join(systemRoot, "System32", "subst.exe");
+            }
+        }
+    }
+}

src/libraries/System.IO.FileSystem.DriveInfo/tests/DriveInfo.Unix.Tests.cs

@@ -5,7 +5,7 @@
 using System.Linq;
 using Xunit;
 
-namespace System.IO.FileSystem.DriveInfoTests
+namespace System.IO.FileSystem.Tests
 {
     public partial class DriveInfoUnixTests
     {

src/libraries/System.IO.FileSystem.DriveInfo/tests/DriveInfo.Windows.Tests.cs

@@ -1,18 +1,17 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System;
-using System.IO;
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.InteropServices;
 using System.Security;
-using Xunit;
 using System.Text;
+using Xunit;
 
-namespace System.IO.FileSystem.DriveInfoTests
+namespace System.IO.FileSystem.Tests
 {
+    [PlatformSpecific(TestPlatforms.Windows)]
     public class DriveInfoWindowsTests
     {
         [Theory]
@@ -35,7 +34,6 @@ public void Ctor_InvalidPath_ThrowsArgumentException(string driveName)
         }
 
         [Fact]
-        [PlatformSpecific(TestPlatforms.Windows)]
         public void TestConstructor()
         {
             string[] variableInput = { "{0}", "{0}", "{0}:", "{0}:", @"{0}:\", @"{0}:\\", "{0}://" };
@@ -54,7 +52,6 @@ public void TestConstructor()
         }
 
         [Fact]
-        [PlatformSpecific(TestPlatforms.Windows)]
         public void TestGetDrives()
         {
             var validExpectedDrives = GetValidDriveLettersOnMachine();
@@ -97,7 +94,6 @@ public void TestDriveProperties_AppContainer()
         }
 
         [Fact]
-        [PlatformSpecific(TestPlatforms.Windows)]
         public void TestDriveFormat()
         {
             DriveInfo validDrive = DriveInfo.GetDrives().Where(d => d.DriveType == DriveType.Fixed).First();
@@ -124,7 +120,6 @@ public void TestDriveFormat()
         }
 
         [Fact]
-        [PlatformSpecific(TestPlatforms.Windows)]
         public void TestDriveType()
         {
             var validDrive = DriveInfo.GetDrives().Where(d => d.DriveType == DriveType.Fixed).First();
@@ -137,7 +132,6 @@ public void TestDriveType()
         }
 
         [Fact]
-        [PlatformSpecific(TestPlatforms.Windows)]
         public void TestValidDiskSpaceProperties()
         {
             bool win32Result;
@@ -169,7 +163,6 @@ public void TestValidDiskSpaceProperties()
         }
 
         [Fact]
-        [PlatformSpecific(TestPlatforms.Windows)]
         public void TestInvalidDiskProperties()
         {
             string invalidDriveName = GetInvalidDriveLettersOnMachine().First().ToString();
@@ -189,7 +182,6 @@ public void TestInvalidDiskProperties()
         }
 
         [Fact]
-        [PlatformSpecific(TestPlatforms.Windows)]
         public void GetVolumeLabel_Returns_CorrectLabel()
         {
             void DoDriveCheck()
@@ -225,7 +217,6 @@ void DoDriveCheck()
         }
 
         [Fact]
-        [PlatformSpecific(TestPlatforms.Windows)]
         public void SetVolumeLabel_Roundtrips()
         {
             DriveInfo drive = DriveInfo.GetDrives().Where(d => d.DriveType == DriveType.Fixed).First();
@@ -246,7 +237,6 @@ public void SetVolumeLabel_Roundtrips()
         }
 
         [Fact]
-        [PlatformSpecific(TestPlatforms.Windows)]
         public void VolumeLabelOnNetworkOrCdRom_Throws()
         {
             // Test setting the volume label on a Network or CD-ROM

src/libraries/System.IO.FileSystem.DriveInfo/tests/System.IO.FileSystem.DriveInfo.Tests.csproj

@@ -5,5 +5,7 @@
   <ItemGroup>
     <Compile Include="DriveInfo.Unix.Tests.cs" Condition="'$(TargetsUnix)' == 'true' or '$(TargetsBrowser)' == 'true'" />
     <Compile Include="DriveInfo.Windows.Tests.cs" Condition="'$(TargetsWindows)' == 'true'" />
+    <Compile Include="VirtualDrives.Windows.Tests.cs" Condition="'$(TargetsWindows)' == 'true'" />
+    <Compile Include="$(CommonTestPath)System\IO\VirtualDriveHelper.Windows.cs" Link="Common\System\IO\VirtualDriveHelper.Windows.cs" Condition="'$(TargetsWindows)' == 'true'" />
   </ItemGroup>
 </Project>

src/libraries/System.IO.FileSystem.DriveInfo/tests/VirtualDrives.Windows.Tests.cs

@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Text;
+using Xunit;
+
+namespace System.IO.FileSystem.Tests
+{
+    // Separate class from the rest of the DriveInfo tests to prevent adding an extra virtual drive to GetDrives().
+    public class DriveInfoVirtualDriveTests
+    {
+        // Cannot set the volume label on a SUBST'ed folder
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsSubstAvailable))]
+        [PlatformSpecific(TestPlatforms.Windows)]
+        public void SetVolumeLabel_OnVirtualDrive_Throws()
+        {
+            using VirtualDriveHelper virtualDrive = new();
+            char letter = virtualDrive.VirtualDriveLetter; // Trigger calling subst
+            DriveInfo drive = DriveInfo.GetDrives().Where(d => d.RootDirectory.FullName[0] == letter).FirstOrDefault();
+            Assert.NotNull(drive);
+            Assert.Throws<IOException>(() => drive.VolumeLabel = "impossible");
+        }
+    }
+}

src/libraries/System.IO.FileSystem/tests/PortedCommon/ReparsePointUtilities.cs

@@ -61,61 +61,6 @@ public static bool CreateJunction(string junctionPath, string targetPath)
         return RunProcess(CreateProcessStartInfo("cmd", "/c", "mklink", "/J", junctionPath, targetPath));
     }
 
-    ///<summary>
-    /// On Windows, mounts a folder to an assigned virtual drive letter using the subst command.
-    /// subst is not available in Windows Nano.
-    /// </summary>
-    public static char CreateVirtualDrive(string targetDir)
-    {
-        if (!OperatingSystem.IsWindows())
-        {
-            throw new PlatformNotSupportedException();
-        }
-
-        char driveLetter = GetNextAvailableDriveLetter();
-        bool success = RunProcess(CreateProcessStartInfo("cmd", "/c", SubstPath, $"{driveLetter}:", targetDir));
-        if (!success || !DriveInfo.GetDrives().Any(x => x.Name[0] == driveLetter))
-        {
-            throw new InvalidOperationException($"Could not create virtual drive {driveLetter}: with subst");
-        }
-        return driveLetter;
-
-        // Finds the next unused drive letter and returns it.
-        char GetNextAvailableDriveLetter()
-        {
-            List<char> existingDrives = DriveInfo.GetDrives().Select(x => x.Name[0]).ToList();
-
-            // A,B are reserved, C is usually reserved
-            IEnumerable<int> range = Enumerable.Range('D', 'Z' - 'D');
-            IEnumerable<char> castRange = range.Select(x => Convert.ToChar(x));
-            IEnumerable<char> allDrivesLetters = castRange.Except(existingDrives);
-
-            if (!allDrivesLetters.Any())
-            {
-                throw new ArgumentOutOfRangeException("No drive letters available");
-            }
-
-            return allDrivesLetters.First();
-        }
-    }
-
-    /// <summary>
-    /// On Windows, unassigns the specified virtual drive letter from its mounted folder.
-    /// </summary>
-    public static void DeleteVirtualDrive(char driveLetter)
-    {
-        if (!OperatingSystem.IsWindows())
-        {
-            throw new PlatformNotSupportedException();
-        }
-
-        bool success = RunProcess(CreateProcessStartInfo("cmd", "/c", SubstPath, "/d", $"{driveLetter}:"));
-        if (!success || DriveInfo.GetDrives().Any(x => x.Name[0] == driveLetter))
-        {
-            throw new InvalidOperationException($"Could not delete virtual drive {driveLetter}: with subst");
-        }
-    }
-
     public static void Mount(string volumeName, string mountPoint)
     {
         if (volumeName[volumeName.Length - 1] != Path.DirectorySeparatorChar)
@@ -173,21 +118,6 @@ private static bool RunProcess(ProcessStartInfo startInfo)
         return process.ExitCode == 0;
     }
 
-    private static string SubstPath
-    {
-        get
-        {
-            if (!OperatingSystem.IsWindows())
-            {
-                throw new PlatformNotSupportedException();
-            }
-
-            string systemRoot = Environment.GetEnvironmentVariable("SystemRoot") ?? @"C:\Windows";
-            string system32 = Path.Join(systemRoot, "System32");
-            return Path.Join(system32, "subst.exe");
-        }
-    }
-
     /// For standalone debugging help. Change Main0 to Main
     public static void Main0(string[] args)
     {

src/libraries/System.IO.FileSystem/tests/System.IO.FileSystem.Tests.csproj

@@ -97,6 +97,7 @@
     <Compile Include="$(CommonPath)System\Text\ValueStringBuilder.cs" Link="Common\System\Text\ValueStringBuilder.cs" />
     <Compile Include="$(CommonPath)System\IO\PathInternal.cs" Link="Common\System\IO\PathInternal.cs" />
     <Compile Include="$(CommonPath)System\IO\PathInternal.Windows.cs" Link="Common\System\IO\PathInternal.Windows.cs" />
+    <Compile Include="$(CommonTestPath)System\IO\VirtualDriveHelper.Windows.cs" Link="Common\System\IO\VirtualDriveHelper.Windows.cs" />
     <ProjectReference Include="$(LibrariesProjectRoot)System.ServiceProcess.ServiceController\src\System.ServiceProcess.ServiceController.csproj" />
     <ProjectReference Include="$(LibrariesProjectRoot)System.IO.FileSystem.AccessControl\src\System.IO.FileSystem.AccessControl.csproj" />
   </ItemGroup>