Fix SDK installation suggestion for already-installed versions

src/Microsoft.VisualStudio.ProjectSystem.Managed.VS/ProjectSystem/VS/Debug/ProjectLaunchTargetsProvider.cs

@@ -8,7 +8,6 @@
 using Microsoft.VisualStudio.ProjectSystem.Debug;
 using Microsoft.VisualStudio.ProjectSystem.HotReload;
 using Microsoft.VisualStudio.ProjectSystem.Properties;
-using Microsoft.VisualStudio.ProjectSystem.Utilities;
 using Microsoft.VisualStudio.ProjectSystem.VS.HotReload;
 using Microsoft.VisualStudio.Shell.Interop;
 using Newtonsoft.Json;
@@ -36,7 +35,7 @@ internal class ProjectLaunchTargetsProvider :
     private readonly IUnconfiguredProjectVsServices _unconfiguredProjectVsServices;
     private readonly IDebugTokenReplacer _tokenReplacer;
     private readonly IFileSystem _fileSystem;
-    private readonly IEnvironmentHelper _environment;
+    private readonly IEnvironment _environment;
     private readonly IActiveDebugFrameworkServices _activeDebugFramework;
     private readonly IProjectThreadingService _threadingService;
     private readonly IVsUIService<IVsDebugger10> _debugger;
@@ -50,7 +49,7 @@ public ProjectLaunchTargetsProvider(
         ConfiguredProject project,
         IDebugTokenReplacer tokenReplacer,
         IFileSystem fileSystem,
-        IEnvironmentHelper environment,
+        IEnvironment environment,
         IActiveDebugFrameworkServices activeDebugFramework,
         IOutputTypeChecker outputTypeChecker,
         IProjectThreadingService threadingService,

src/Microsoft.VisualStudio.ProjectSystem.Managed.VS/ProjectSystem/VS/Retargeting/ProjectRetargetHandler.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. See the LICENSE.md file in the project root for more information.
 
 using System.Text.Json;
+using Microsoft.VisualStudio.ProjectSystem.VS.Setup;
 using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.Interop;
 using Microsoft.VisualStudio.Threading;
@@ -18,6 +19,7 @@ internal sealed partial class ProjectRetargetHandler : IProjectRetargetHandler,
     private readonly IProjectThreadingService _projectThreadingService;
     private readonly IVsService<SVsTrackProjectRetargeting, IVsTrackProjectRetargeting2> _projectRetargetingService;
     private readonly IVsService<SVsSolution, IVsSolution> _solutionService;
+    private readonly IDotNetEnvironment _dotnetEnvironment;
 
     private Guid _currentSdkDescriptionId = Guid.Empty;
     private Guid _sdkRetargetId = Guid.Empty;
@@ -28,13 +30,15 @@ public ProjectRetargetHandler(
         IFileSystem fileSystem,
         IProjectThreadingService projectThreadingService,
         IVsService<SVsTrackProjectRetargeting, IVsTrackProjectRetargeting2> projectRetargetingService,
-        IVsService<SVsSolution, IVsSolution> solutionService)
+        IVsService<SVsSolution, IVsSolution> solutionService,
+        IDotNetEnvironment dotnetEnvironment)
     {
         _releasesProvider = releasesProvider;
         _fileSystem = fileSystem;
         _projectThreadingService = projectThreadingService;
         _projectRetargetingService = projectRetargetingService;
         _solutionService = solutionService;
+        _dotnetEnvironment = dotnetEnvironment;
     }
 
     public Task<IProjectTargetChange?> CheckForRetargetAsync(RetargetCheckOptions options)
@@ -89,6 +93,12 @@ public Task RetargetAsync(TextWriter outputLogger, RetargetOptions options, IPro
             return null;
         }
 
+        // Check if the retarget is already installed globally
+        if (_dotnetEnvironment.IsSdkInstalled(retargetVersion))
+        {
+            return null;
+        }
+
         if (_currentSdkDescriptionId == Guid.Empty)
         {
             // register the current and retarget versions, note there is a bug in the current implementation
@@ -142,7 +152,7 @@ public Task RetargetAsync(TextWriter outputLogger, RetargetOptions options, IPro
             {
                 try
                 {
-                    using Stream stream = File.OpenRead(globalJsonPath);
+                    using Stream stream = _fileSystem.OpenTextStream(globalJsonPath);
                     using JsonDocument doc = await JsonDocument.ParseAsync(stream);
                     if (doc.RootElement.TryGetProperty("sdk", out JsonElement sdkProp) &&
                         sdkProp.TryGetProperty("version", out JsonElement versionProp))

src/Microsoft.VisualStudio.ProjectSystem.Managed.VS/ProjectSystem/VS/Setup/DotNetEnvironment.cs

@@ -0,0 +1,123 @@
+// Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. See the LICENSE.md file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using IFileSystem = Microsoft.VisualStudio.IO.IFileSystem;
+using IRegistry = Microsoft.VisualStudio.ProjectSystem.VS.Utilities.IRegistry;
+
+namespace Microsoft.VisualStudio.ProjectSystem.VS.Setup;
+
+/// <summary>
+/// Provides information about the .NET environment and installed SDKs by querying the Windows registry.
+/// </summary>
+[Export(typeof(IDotNetEnvironment))]
+internal class DotNetEnvironment : IDotNetEnvironment
+{
+    private readonly IFileSystem _fileSystem;
+    private readonly IRegistry _registry;
+    private readonly IEnvironment _environment;
+
+    [ImportingConstructor]
+    public DotNetEnvironment(IFileSystem fileSystem, IRegistry registry, IEnvironment environment)
+    {
+        _fileSystem = fileSystem;
+        _registry = registry;
+        _environment = environment;
+    }
+
+    /// <inheritdoc/>
+    public bool IsSdkInstalled(string sdkVersion)
+    {
+        try
+        {
+            string archSubKey = GetArchitectureSubKey(_environment.ProcessArchitecture);
+            string registryKey = $@"SOFTWARE\dotnet\Setup\InstalledVersions\{archSubKey}\sdk";
+
+            // Get all value names from the sdk subkey
+            string[] installedVersions = _registry.GetValueNames(
+                Win32.RegistryHive.LocalMachine,
+                Win32.RegistryView.Registry32,
+                registryKey);
+
+            // Check if the requested SDK version is in the list
+            foreach (string installedVersion in installedVersions)
+            {
+                if (string.Equals(installedVersion, sdkVersion, StringComparison.OrdinalIgnoreCase))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+        catch
+        {
+            // If we fail to check, assume the SDK is not installed
+            return false;
+        }
+    }
+
+    /// <inheritdoc/>
+    public string? GetDotNetHostPath()
+    {
+        // First check the registry
+        string archSubKey = GetArchitectureSubKey(_environment.ProcessArchitecture);
+        string registryKey = $@"SOFTWARE\dotnet\Setup\InstalledVersions\{archSubKey}";
+
+        string? installLocation = _registry.GetValue(
+            Win32.RegistryHive.LocalMachine,
+            Win32.RegistryView.Registry32,
+            registryKey,
+            "InstallLocation");
+
+        if (!string.IsNullOrEmpty(installLocation))
+        {
+            string dotnetExePath = Path.Combine(installLocation, "dotnet.exe");
+            if (_fileSystem.FileExists(dotnetExePath))
+            {
+                return dotnetExePath;
+            }
+        }
+
+        // Fallback to Program Files
+        string? programFiles = _environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles);
+        if (programFiles is not null)
+        {
+            string dotnetPath = Path.Combine(programFiles, "dotnet", "dotnet.exe");
+
+            if (_fileSystem.FileExists(dotnetPath))
+            {
+                return dotnetPath;
+            }
+        }
+
+        return null;
+    }
+
+    /// <inheritdoc/>
+    public string[]? GetInstalledRuntimeVersions(Architecture architecture)
+    {
+        // https://github.com/dotnet/designs/blob/96d2ddad13dcb795ff2c5c6a051753363bdfcf7d/accepted/2020/install-locations.md#globally-registered-install-location-new
+
+        string archSubKey = GetArchitectureSubKey(architecture);
+        string registryKey = $@"SOFTWARE\dotnet\Setup\InstalledVersions\{archSubKey}\sharedfx\Microsoft.NETCore.App";
+
+        string[] valueNames = _registry.GetValueNames(
+            Win32.RegistryHive.LocalMachine,
+            Win32.RegistryView.Registry32,
+            registryKey);
+
+        return valueNames.Length == 0 ? null : valueNames;
+    }
+
+    private static string GetArchitectureSubKey(Architecture architecture)
+    {
+        return architecture switch
+        {
+            Architecture.X86 => "x86",
+            Architecture.X64 => "x64",
+            Architecture.Arm => "arm",
+            Architecture.Arm64 => "arm64",
+            _ => architecture.ToString().ToLower()
+        };
+    }
+}

src/Microsoft.VisualStudio.ProjectSystem.Managed.VS/ProjectSystem/VS/Setup/IDotNetEnvironment.cs

@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. See the LICENSE.md file in the project root for more information.
+
+namespace Microsoft.VisualStudio.ProjectSystem.VS.Setup;
+
+/// <summary>
+/// Provides information about the .NET environment and installed SDKs.
+/// </summary>
+[ProjectSystemContract(ProjectSystemContractScope.Global, ProjectSystemContractProvider.Private, Cardinality = ImportCardinality.ExactlyOne)]
+internal interface IDotNetEnvironment
+{
+    /// <summary>
+    /// Checks if a specific .NET SDK version is installed on the system.
+    /// </summary>
+    /// <param name="sdkVersion">The SDK version to check for (e.g., "8.0.415").</param>
+    /// <returns>
+    /// A task that represents the asynchronous operation. The task result contains 
+    /// <see langword="true"/> if the SDK version is installed; otherwise, <see langword="false"/>.
+    /// </returns>
+    bool IsSdkInstalled(string sdkVersion);
+
+    /// <summary>
+    /// Gets the path to the dotnet.exe executable.
+    /// </summary>
+    /// <returns>
+    /// The full path to dotnet.exe if found; otherwise, <see langword="null"/>.
+    /// </returns>
+    string? GetDotNetHostPath();
+
+    /// <summary>
+    /// Reads the list of installed .NET Core runtimes for the specified architecture from the registry.
+    /// </summary>
+    /// <remarks>
+    /// Returns runtimes installed both as standalone packages, and through VS Setup.
+    /// Values have the form <c>3.1.32</c>, <c>7.0.11</c>, <c>8.0.0-preview.7.23375.6</c>, <c>8.0.0-rc.1.23419.4</c>.
+    /// If results could not be determined, <see langword="null"/> is returned.
+    /// </remarks>
+    /// <param name="architecture">The runtime architecture to report results for.</param>
+    /// <returns>An array of runtime versions, or <see langword="null"/> if results could not be determined or no runtimes were found.</returns>
+    string[]? GetInstalledRuntimeVersions(System.Runtime.InteropServices.Architecture architecture);
+}

src/Microsoft.VisualStudio.ProjectSystem.Managed.VS/ProjectSystem/VS/Setup/SetupComponentRegistrationService.cs

@@ -43,6 +43,7 @@ public SetupComponentRegistrationService(
         IVsService<SVsSetupCompositionService, IVsSetupCompositionService> vsSetupCompositionService,
         ISolutionService solutionService,
         IProjectFaultHandlerService projectFaultHandlerService,
+        IDotNetEnvironment dotnetEnvironment,
         JoinableTaskContext joinableTaskContext)
         : base(new(joinableTaskContext))
     {
@@ -51,9 +52,9 @@ public SetupComponentRegistrationService(
         _solutionService = solutionService;
         _projectFaultHandlerService = projectFaultHandlerService;
 
-        _installedRuntimeComponentIds = new Lazy<HashSet<string>?>(FindInstalledRuntimeComponentIds);
+        _installedRuntimeComponentIds = new Lazy<HashSet<string>?>(() => FindInstalledRuntimeComponentIds(dotnetEnvironment));
 
-        static HashSet<string>? FindInstalledRuntimeComponentIds()
+        static HashSet<string>? FindInstalledRuntimeComponentIds(IDotNetEnvironment dotnetEnvironment)
         {
             // Workaround for https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1460328
             // VS Setup doesn't know about runtimes installed outside of VS. Deep detection is not suggested for performance reasons.
@@ -66,7 +67,7 @@ public SetupComponentRegistrationService(
             // TODO consider the architecture of the project itself
             Architecture architecture = RuntimeInformation.ProcessArchitecture;
 
-            string[]? runtimeVersions = NetCoreRuntimeVersionsRegistryReader.ReadRuntimeVersionsInstalledInLocalMachine(architecture);
+            string[]? runtimeVersions = dotnetEnvironment.GetInstalledRuntimeVersions(architecture);
 
             if (runtimeVersions is null)
             {

src/Microsoft.VisualStudio.ProjectSystem.Managed.VS/ProjectSystem/VS/Utilities/IRegistry.cs

@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. See the LICENSE.md file in the project root for more information.
+
+using Microsoft.Win32;
+
+namespace Microsoft.VisualStudio.ProjectSystem.VS.Utilities;
+
+/// <summary>
+/// Provides access to the Windows registry in a testable manner.
+/// </summary>
+[ProjectSystem.ProjectSystemContract(ProjectSystem.ProjectSystemContractScope.Global, ProjectSystem.ProjectSystemContractProvider.Private, Cardinality = ImportCardinality.ExactlyOne)]
+internal interface IRegistry
+{
+    /// <summary>
+    /// Opens a registry key with the specified path under the given base key.
+    /// </summary>
+    /// <param name="hive">The registry hive to open (e.g., LocalMachine, CurrentUser).</param>
+    /// <param name="view">The registry view to use (e.g., Registry32, Registry64).</param>
+    /// <param name="subKeyPath">The path to the subkey to open.</param>
+    /// <param name="valueName">The name of the value to retrieve.</param>
+    /// <returns>
+    /// The registry key value as a string if found; otherwise, <see langword="null"/>.
+    /// </returns>
+    string? GetValue(RegistryHive hive, RegistryView view, string subKeyPath, string valueName);
+
+    /// <summary>
+    /// Gets the names of all values under the specified registry key.
+    /// </summary>
+    /// <param name="hive">The registry hive to open (e.g., LocalMachine, CurrentUser).</param>
+    /// <param name="view">The registry view to use (e.g., Registry32, Registry64).</param>
+    /// <param name="subKeyPath">The path to the subkey to open.</param>
+    /// <returns>
+    /// An array of value names if the key exists; otherwise, an empty array.
+    /// </returns>
+    string[] GetValueNames(RegistryHive hive, RegistryView view, string subKeyPath);
+}

src/Microsoft.VisualStudio.ProjectSystem.Managed.VS/ProjectSystem/VS/Utilities/RegistryService.cs

@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. See the LICENSE.md file in the project root for more information.
+
+using Microsoft.Win32;
+
+namespace Microsoft.VisualStudio.ProjectSystem.VS.Utilities;
+
+/// <summary>
+/// Provides access to the Windows registry.
+/// </summary>
+[Export(typeof(IRegistry))]
+internal class RegistryService : IRegistry
+{
+    /// <inheritdoc/>
+    public string? GetValue(RegistryHive hive, RegistryView view, string subKeyPath, string valueName)
+    {
+        using RegistryKey? subKey = OpenSubKey(hive, view, subKeyPath);
+        return subKey?.GetValue(valueName) as string;
+    }
+
+    /// <inheritdoc/>
+    public string[] GetValueNames(RegistryHive hive, RegistryView view, string subKeyPath)
+    {
+        using RegistryKey? subKey = OpenSubKey(hive, view, subKeyPath);
+        return subKey?.GetValueNames() ?? [];
+    }
+
+    private static RegistryKey? OpenSubKey(RegistryHive hive, RegistryView view, string subKeyPath)
+    {
+        try
+        {
+            using RegistryKey baseKey = RegistryKey.OpenBaseKey(hive, view);
+            return baseKey.OpenSubKey(subKeyPath);
+        }
+        catch (Exception ex) when (ex.IsCatchable())
+        {
+            // Return null on catchable registry access errors
+            return null;
+        }
+    }
+}