Show modified shell in dotnetup to explain modes

src/Installer/Microsoft.Dotnet.Installation/DotnetInstallException.cs

@@ -133,6 +133,12 @@ public enum DotnetInstallErrorCode
     /// Distinct from <see cref="NoMatchingReleaseFileForPlatform"/>
     /// </summary>
     NoUserInstallableArtifact,
+
+    /// <summary>
+    /// An access mode reached a workflow that does not support it, indicating inconsistent
+    /// product state rather than invalid user input.
+    /// </summary>
+    InvalidModeSelection,
 }
 
 /// <summary>

src/Installer/dotnetup.Library/Commands/Init/InitWorkflowDefaults.cs

@@ -28,7 +28,11 @@ public static WalkthroughPlan ResolveWalkthroughPlan(
         List<ResolvedInstallRequest>? preResolvedRequests,
         IDotnetEnvironmentManager dotnetEnvironment)
     {
-        DotnetAccessMode accessMode = GetDefaultAccessMode(command.ShellProvider);
+        IEnvShellProvider? shellProvider = command.ShellProvider ?? ShellDetection.GetCurrentShellProvider();
+        DotnetAccessMode accessMode = GetDefaultAccessMode(shellProvider);
+        var globalJson = GlobalJsonModifier.GetGlobalJsonInfo(Environment.CurrentDirectory);
+        var pathResolution = new InstallPathResolver(dotnetEnvironment).Resolve(
+            command.InstallPath, globalJson);
 
         if (preResolvedRequests is { Count: > 0 })
         {
@@ -41,22 +45,36 @@ public static WalkthroughPlan ResolveWalkthroughPlan(
                 resolvedRoot,
                 accessMode,
                 resolvedMigrations,
-                new DefaultChannelDisplay(first.Request.Channel.Name, first.Request.Options.GlobalJsonPath));
+                new DefaultChannelDisplay(first.Request.Channel.Name, first.Request.Options.GlobalJsonPath),
+                shellProvider,
+                GetInstallRootGlobalJsonPath(pathResolution, globalJson, resolvedRoot));
         }
 
-        var globalJson = GlobalJsonModifier.GetGlobalJsonInfo(Environment.CurrentDirectory);
-        var pathResolution = new InstallPathResolver(dotnetEnvironment).Resolve(
-            command.InstallPath, globalJson);
         var installRoot = new DotnetInstallRoot(
             pathResolution.ResolvedInstallPath,
             InstallerUtilities.GetDefaultInstallArchitecture());
 
         var migrations = ResolveDefaultMigrations(
             dotnetEnvironment, accessMode, installRoot, command.ManifestPath, existingRequests: null);
 
-        return new WalkthroughPlan(installRoot, accessMode, migrations, ResolveChannelDisplay(globalJson));
+        return new WalkthroughPlan(
+            installRoot,
+            accessMode,
+            migrations,
+            ResolveChannelDisplay(globalJson),
+            shellProvider,
+            GetInstallRootGlobalJsonPath(pathResolution, globalJson, installRoot));
     }
 
+    private static string? GetInstallRootGlobalJsonPath(
+        InstallPathResolver.InstallPathResolutionResult pathResolution,
+        GlobalJsonInfo globalJson,
+        DotnetInstallRoot installRoot)
+        => pathResolution.PathSource is PathSource.GlobalJson
+            && DotnetupUtilities.PathsEqual(pathResolution.ResolvedInstallPath, installRoot.Path)
+                ? globalJson.GlobalJsonPath
+                : null;
+
     /// <summary>
     /// Resolves the default install requests. Uses the pre-resolved requests when supplied;
     /// otherwise resolves the default SDK channel (from global.json or "latest"). This performs

src/Installer/dotnetup.Library/Commands/Init/WalkthroughPlan.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using Microsoft.DotNet.Tools.Bootstrapper.Commands.Shared;
+using Microsoft.DotNet.Tools.Bootstrapper.Shell;
 
 namespace Microsoft.DotNet.Tools.Bootstrapper.Commands.Init;
 
@@ -15,8 +16,12 @@ namespace Microsoft.DotNet.Tools.Bootstrapper.Commands.Init;
 /// <param name="AccessMode">The recommended access mode.</param>
 /// <param name="Migrations">The system installs eligible for migration under the recommended mode.</param>
 /// <param name="ChannelDisplay">Display information for the SDK channel line.</param>
+/// <param name="ShellProvider">The resolved shell provider used to recommend and describe terminal mode.</param>
+/// <param name="InstallRootGlobalJsonPath">The global.json that supplied the install root, if any.</param>
 internal sealed record WalkthroughPlan(
     DotnetInstallRoot InstallRoot,
     DotnetAccessMode AccessMode,
     List<MigrationWorkflow.MigrationSelection> Migrations,
-    DefaultChannelDisplay ChannelDisplay);
+    DefaultChannelDisplay ChannelDisplay,
+    IEnvShellProvider? ShellProvider,
+    string? InstallRootGlobalJsonPath);

src/Installer/dotnetup.Library/Commands/Init/WalkthroughSummary.cs

@@ -3,6 +3,7 @@
 
 using System.Globalization;
 using Microsoft.DotNet.Tools.Bootstrapper.Commands.Shared;
+using Microsoft.DotNet.Tools.Bootstrapper.Shell;
 using Spectre.Console;
 using SpectreAnsiConsole = Spectre.Console.AnsiConsole;
 
@@ -97,11 +98,62 @@ private static void RenderSummaryBlock(WalkthroughPlan plan, DotnetAccessMode? c
 
         RenderChannelLine(plan.ChannelDisplay);
         RenderModeLine(plan.AccessMode, configuredAccessMode);
+        SpectreAnsiConsole.WriteLine();
+        SpectreAnsiConsole.MarkupLine(BuildModeDescription(plan));
         RenderMigrationSummary(plan.Migrations);
 
         SpectreAnsiConsole.WriteLine();
     }
 
+    internal static string BuildModeDescription(WalkthroughPlan plan)
+    {
+        string mode = DotnetupTheme.Accent(DotnetAccessModeDisplay.GetName(plan.AccessMode).EscapeMarkup());
+
+        if (plan.AccessMode is DotnetAccessMode.None)
+        {
+            string currentShell = DotnetupTheme.Accent(ShellDetection.GetCurrentShellDisplayName().EscapeMarkup());
+            string supportedShells = DotnetupTheme.Accent(
+                string.Join(", ", ShellDetection.s_supportedShells.Select(shell => shell.ArgumentName)).EscapeMarkup());
+
+            return string.Format(
+                CultureInfo.InvariantCulture,
+                Strings.SummaryModeUnsupportedShell,
+                mode,
+                currentShell,
+                supportedShells);
+        }
+
+        string configurationTarget = plan.AccessMode switch
+        {
+            DotnetAccessMode.Shell when plan.ShellProvider is { } shellProvider => string.Join(
+                ", ",
+                shellProvider.GetProfilePaths().Select(path => DotnetupTheme.Accent(path.EscapeMarkup()))),
+            DotnetAccessMode.Everywhere => DotnetupTheme.Accent(
+                Strings.SummaryModeSystemEnvironmentVariables.EscapeMarkup()),
+            _ => throw new DotnetInstallException(
+                DotnetInstallErrorCode.InvalidModeSelection,
+                $"Unable to describe access mode '{plan.AccessMode}' with the resolved shell provider."),
+        };
+
+        string installRoot = DotnetupTheme.Accent(plan.InstallRoot.Path.EscapeMarkup());
+        if (plan.InstallRootGlobalJsonPath is { } globalJsonPath)
+        {
+            installRoot += " " + DotnetupTheme.Dim(string.Format(
+                CultureInfo.InvariantCulture,
+                Strings.SummaryModeInstallRootGlobalJsonSuffix,
+                globalJsonPath.EscapeMarkup()));
+        }
+
+        return string.Format(
+            CultureInfo.InvariantCulture,
+            Strings.SummaryModeConfiguration,
+            mode,
+            configurationTarget,
+            DotnetupTheme.Accent("PATH"),
+            DotnetupTheme.Accent("DOTNET_ROOT"),
+            installRoot);
+    }
+
     private static void RenderChannelLine(DefaultChannelDisplay channel)
     {
         if (channel.ChannelLabel is null)

src/Installer/dotnetup.Library/Strings.resx

@@ -450,6 +450,21 @@ Or open a new terminal.</value>
     <value>current: {0}</value>
     <comment>{0} is the user's currently configured mode name. Shown in parentheses after the recommended mode.</comment>
   </data>
+  <data name="SummaryModeConfiguration" xml:space="preserve">
+    <value>{0} modifies {1} to set {2} and {3} to prefer {4}.</value>
+    <comment>{0} is the suggested mode name; {1} is one or more shell profile paths or the system environment variables; {2} is PATH; {3} is DOTNET_ROOT; {4} is the dotnetup install path.</comment>
+  </data>
+  <data name="SummaryModeSystemEnvironmentVariables" xml:space="preserve">
+    <value>the system environment variables</value>
+  </data>
+  <data name="SummaryModeInstallRootGlobalJsonSuffix" xml:space="preserve">
+    <value>(inferred from {0})</value>
+    <comment>{0} is the path to the global.json file that supplied the dotnetup install root.</comment>
+  </data>
+  <data name="SummaryModeUnsupportedShell" xml:space="preserve">
+    <value>{0} is suggested because the current shell ({1}) cannot be detected or is not supported. Supported shells: {2}.</value>
+    <comment>{0} is the suggested isolation mode name; {1} is the current SHELL value or "(not set)"; {2} is the list of supported shell names.</comment>
+  </data>
   <data name="SummaryMigrateHeader" xml:space="preserve">
     <value>System installs to migrate:</value>
   </data>

src/Installer/dotnetup.Library/Telemetry/ErrorCategoryClassifier.cs

@@ -57,6 +57,7 @@ internal static ErrorCategory ClassifyInstallError(DotnetInstallErrorCode errorC
             DotnetInstallErrorCode.UninstallTargetNotFound => ErrorCategory.User,
             DotnetInstallErrorCode.UnsignedDownloadBlockedByPolicy => ErrorCategory.User,
             DotnetInstallErrorCode.NoUserInstallableArtifact => ErrorCategory.User,
+            DotnetInstallErrorCode.InvalidModeSelection => ErrorCategory.Product,
             DotnetInstallErrorCode.Unknown => ErrorCategory.Product,
 
             _ => ErrorCategory.Product