Respect -WhatIf in PowerShell package commands

doc/ReleaseNotes.md

@@ -45,6 +45,10 @@ For aliases requested through `--rename`, `Commands`, or `PortableCommandAlias`,
 This change resolves alias failures in non-symlinked scenarios, including cases where WinGet adds the install directory to `PATH` instead of creating links.
 Because the alias is now created as an executable hardlink in the install location, command aliases remain available and consistent even when symlink creation is skipped.
 
+### PowerShell `-WhatIf`
+
+PowerShell package commands now honor `-WhatIf` and do not perform package operations during preview.
+
 ### Minor Bug Fixes
 * Fixed REST search results bypassing locally verifiable package filters and selectors. Extra manifests are retrieved only for complete source result sets of three or fewer packages. Normalized name/publisher criteria remain unvalidated client-side.
 * Fixed installed-package matching incorrectly combining names and publishers from different manifest entries.

src/PowerShell/CommonFiles/PowerShellCmdlet.cs

@@ -502,13 +502,12 @@ internal void SetVariable(string variableName, object value)
         /// <returns>If the operation should continue.</returns>
         internal bool ShouldProcess(string target)
         {
-            // If not on the main thread just continue.
-            if (this.pwshThread != Thread.CurrentThread)
+            bool shouldProcess = false;
+            this.ExecuteInPowerShellThread(() =>
             {
-                return true;
-            }
-
-            return this.psCmdlet.ShouldProcess(target);
+                shouldProcess = this.psCmdlet.ShouldProcess(target);
+            });
+            return shouldProcess;
         }
 
         private void Complete()

src/PowerShell/tests/Microsoft.WinGet.Client.Tests.ps1

@@ -298,11 +298,34 @@ Describe 'Install|Update|Uninstall-WinGetPackage' {
         }
     }
 
+    It 'Does not install with WhatIf' {
+        $result = Install-WinGetPackage -Id AppInstallerTest.TestExeInstaller -Version '1.0.0.0' -WhatIf
+
+        $result | Should -BeNullOrEmpty
+        (Get-WinGetPackage -Id AppInstallerTest.TestExeInstaller -ErrorAction SilentlyContinue) | Should -BeNullOrEmpty
+    }
+
     It 'Install by Id' {
         $result = Install-WinGetPackage -Id AppInstallerTest.TestExeInstaller -Version '1.0.0.0'
         Validate-WinGetPackageOperationResult $result $expectedExeInstallerResult 'install'
     }
 
+    It 'Does not update with WhatIf' {
+        $installedVersion = (Get-WinGetPackage -Id AppInstallerTest.TestExeInstaller).InstalledVersion
+        $result = Update-WinGetPackage -Id AppInstallerTest.TestExeInstaller -WhatIf
+
+        $result | Should -BeNullOrEmpty
+        (Get-WinGetPackage -Id AppInstallerTest.TestExeInstaller).InstalledVersion | Should -Be $installedVersion
+    }
+
+    It 'Does not uninstall with WhatIf' {
+        $installedVersion = (Get-WinGetPackage -Id AppInstallerTest.TestExeInstaller).InstalledVersion
+        $result = Uninstall-WinGetPackage -Id AppInstallerTest.TestExeInstaller -WhatIf
+
+        $result | Should -BeNullOrEmpty
+        (Get-WinGetPackage -Id AppInstallerTest.TestExeInstaller).InstalledVersion | Should -Be $installedVersion
+    }
+
     It 'Install by exact Name and Version' {
         $result = Install-WinGetPackage -Name TestPortableExe -Version '2.0.0.0' -MatchOption Equals
         Validate-WinGetPackageOperationResult $result $expectedPortableInstallerResult 'install'
@@ -369,6 +392,14 @@ Describe 'Install|Repair|Uninstall-WinGetPackage' {
             Validate-WinGetPackageOperationResult $result $expectedResult 'install'
         }
 
+        It 'Does not repair MSIX with WhatIf' {
+            $installedVersion = (Get-WinGetPackage -Id AppInstallerTest.TestMsixInstaller).InstalledVersion
+            $result = Repair-WinGetPackage -Id AppInstallerTest.TestMsixInstaller -WhatIf
+
+            $result | Should -BeNullOrEmpty
+            (Get-WinGetPackage -Id AppInstallerTest.TestMsixInstaller).InstalledVersion | Should -Be $installedVersion
+        }
+
         It 'Repair MSIX By Id' {
             $result = Repair-WinGetPackage -Id AppInstallerTest.TestMsixInstaller
             Validate-WinGetPackageOperationResult $result $expectedResult 'repair'
@@ -594,6 +625,14 @@ Describe 'Export-WinGetPackage' {
         AddTestSource
     }
 
+    It 'Does not download with WhatIf' {
+        $testDirectory = GetRandomTestDirectory
+        $result = Export-WinGetPackage -Id AppInstallerTest.TestExeInstaller -Version '1.0.0.0' -DownloadDirectory $testDirectory -WhatIf
+
+        $result | Should -BeNullOrEmpty
+        Test-Path -Path $testDirectory | Should -Be $false
+    }
+
     It 'Download by Id' {
         $testDirectory = GetRandomTestDirectory
         $result = Export-WinGetPackage -Id AppInstallerTest.TestExeInstaller -Version '1.0.0.0' -DownloadDirectory $testDirectory