Use GetCurrentPackageFamilyNameNative API instead of path matching to detect MSIX installation (#28029)

src/Microsoft.PowerShell.ConsoleHost/host/msh/ConsoleHost.cs

@@ -378,20 +378,41 @@ namespace Microsoft.PowerShell
 #if UNIX
             const string pwshName = "pwsh";
             const string dotnetToolPathSegment = "/.store/powershell/";
+            const StringComparison procNameCompType = StringComparison.Ordinal;
 #else
             const string pwshName = "pwsh.exe";
             const string dotnetToolPathSegment = @"\.store\powershell\";
+            const StringComparison procNameCompType = StringComparison.OrdinalIgnoreCase;
 #endif
 
             string psExePath = Environment.ProcessPath;
             string psExeHome = Path.GetDirectoryName(psExePath);
             string processName = Path.GetFileName(psExePath);
 
-            // Use 'Environment.ProcessPath' if it points to 'pwsh.exe' or 'pwsh'.
-            if (pwshName.Equals(processName, StringComparison.Ordinal))
+            // Use 'Environment.ProcessPath' if it points to 'pwsh.exe' or 'pwsh'. The 'ProcessPath' on Windows
+            // could be any case as it depends on the `lpCommandLine` argument passed to `CreateProcess`, so we
+            // compare with 'OrdinalIgnoreCase' on Windows.
+            if (pwshName.Equals(processName, procNameCompType))
             {
 #if !UNIX
-                psExeHome = ResolveStablePathIfMsix(psExeHome);
+                // When running from an MSIX package, 'psExeHome' points to the MSIX package folder under "Program Files".
+                //
+                // That path contains a version string and will change with every update. Prepending that path to the PATH
+                // environment variable caused a problem for CMake-based build systems: CMake cached the path to 'pwsh.exe'
+                // when running for the first time from the MSIX PowerShell. That cached path became invalid after the MSIX
+                // PowerShell was updated, which broke CMake.
+                //
+                // So, instead of using the "Program Files" package folder path, we need to use the stable path that contains
+                // the execution alias for the specific MSIX package, e.g. use "%LOCALAPPDATA%\Microsoft\WindowsApps\Microsoft.PowerShell_8wekyb3d8bbwe"
+                // instead of "%ProgramFiles%\WindowsApps\Microsoft.PowerShell_7.x.x.0_x64__8wekyb3d8bbwe".
+                if (Utils.IsMSIXInstallation(out string packageFamilyName))
+                {
+                    string localAppDataDir = Environment.GetFolderPath(
+                        Environment.SpecialFolder.LocalApplicationData,
+                        Environment.SpecialFolderOption.DoNotVerify);
+
+                    psExeHome = $"{localAppDataDir}\\Microsoft\\WindowsApps\\{packageFamilyName}";
+                }
 #endif
                 return psExeHome;
             }
@@ -439,49 +460,6 @@ namespace Microsoft.PowerShell
             }
         }
 #else
-        /// <summary>
-        /// Handle the MSIX package scenario where <paramref name="psExeHome"/> points to the MSIX package folder under "Program Files".
-        ///
-        /// That path contains a version string and will change with every update. Prepending that path to the PATH environment variable
-        /// caused a problem for CMake-based build systems: CMake cached the path to 'pwsh.exe' when running for the first time from the
-        /// MSIX PowerShell. That cached path became invalid after the MSIX PowerShell was updated, which broke CMake.
-        ///
-        /// So, instead of using the "Program Files" package folder path, we need to use the stable path that contains the execution alias
-        /// for the specific MSIX package, e.g. use "%LOCALAPPDATA%\Microsoft\WindowsApps\Microsoft.PowerShell_8wekyb3d8bbwe" instead of
-        /// "%ProgramFiles%\WindowsApps\Microsoft.PowerShell_7.x.x.0_x64__8wekyb3d8bbwe".
-        /// </summary>
-        /// <param name="psExeHome">Path to the directory that contains the pwsh executable.</param>
-        private static string ResolveStablePathIfMsix(string psExeHome)
-        {
-            const string msixPublisherSuffix = "_8wekyb3d8bbwe";
-            const string msixPackageBaseName = "Microsoft.PowerShell";
-
-            if (psExeHome.EndsWith(msixPublisherSuffix, StringComparison.Ordinal))
-            {
-                string programFileDir = Environment.GetFolderPath(
-                    Environment.SpecialFolder.ProgramFiles,
-                    Environment.SpecialFolderOption.DoNotVerify);
-
-                string prefix = $"{programFileDir}\\WindowsApps\\{msixPackageBaseName}";
-                if (psExeHome.StartsWith(prefix, StringComparison.Ordinal))
-                {
-                    int startIndex = prefix.Length;
-                    int underbarIndex = psExeHome.IndexOf('_', startIndex);
-                    if (underbarIndex > 0)
-                    {
-                        ReadOnlySpan<char> channelSuffix = psExeHome.AsSpan(startIndex, underbarIndex - startIndex);
-                        string localAppDataDir = Environment.GetFolderPath(
-                            Environment.SpecialFolder.LocalApplicationData,
-                            Environment.SpecialFolderOption.DoNotVerify);
-
-                        psExeHome = $"{localAppDataDir}\\Microsoft\\WindowsApps\\{msixPackageBaseName}{channelSuffix}{msixPublisherSuffix}";
-                    }
-                }
-            }
-
-            return psExeHome;
-        }
-
         /// <summary>
         /// The break handler for the program.  Dispatches a break event to the current Executor.
         /// </summary>

src/System.Management.Automation/engine/Interop/Windows/GetCurrentPackageFamilyName.cs

@@ -0,0 +1,43 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+#nullable enable
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Windows
+    {
+        [LibraryImport("kernel32.dll", EntryPoint = "GetCurrentPackageFamilyName", StringMarshalling = StringMarshalling.Utf16)]
+        private static partial int GetCurrentPackageFamilyNameNative(ref uint packageFamilyNameLength, Span<char> packageFamilyName);
+
+        /// <summary>
+        /// Returns the package family name of the current process when it has package (MSIX) identity; otherwise null.
+        /// </summary>
+        internal static string? GetCurrentPackageFamilyName()
+        {
+            const int ErrorSuccess = 0;
+            const int PackageFamilyNameMaxLength = 65; // Maximum name plus null terminator.
+
+            try
+            {
+                uint length = PackageFamilyNameMaxLength;
+                Span<char> buffer = stackalloc char[PackageFamilyNameMaxLength];
+                int result = GetCurrentPackageFamilyNameNative(ref length, buffer);
+                if (result is not ErrorSuccess || length is 0)
+                {
+                    return null;
+                }
+
+                // The returned length includes the null terminator, which we don't want in the managed string.
+                return new string(buffer[..(int)(length - 1)]);
+            }
+            catch (Exception exception) when (exception is DllNotFoundException or EntryPointNotFoundException)
+            {
+                return null;
+            }
+        }
+    }
+}

src/System.Management.Automation/engine/Utils.cs

@@ -475,6 +475,27 @@ namespace System.Management.Automation
 
             return string.Empty;
         }
+
+        private static string s_packageFamilyName;
+        private static bool? s_isMSIXInstallation;
+
+        /// <summary>
+        /// Determine whether the current process has package (MSIX) identity, caching the result
+        /// so the native API is only called once.
+        /// </summary>
+        /// <param name="packageFamilyName">Receives the package family name when the process has package identity; otherwise null.</param>
+        /// <returns>True if the current process has package (MSIX) identity; otherwise false.</returns>
+        internal static bool IsMSIXInstallation(out string packageFamilyName)
+        {
+            if (s_isMSIXInstallation is null)
+            {
+                s_packageFamilyName = Interop.Windows.GetCurrentPackageFamilyName();
+                s_isMSIXInstallation = s_packageFamilyName is not null;
+            }
+
+            packageFamilyName = s_packageFamilyName;
+            return s_isMSIXInstallation.Value;
+        }
 #endif
 
         internal static string DefaultPowerShellAppBase => GetApplicationBase(DefaultPowerShellShellID);