Fix Start-Process -PassThru to make sure the ExitCode property is accessible for the returned Process object (#20749) (#20866)

src/Microsoft.PowerShell.Commands.Management/commands/management/Process.cs

@@ -2126,6 +2126,13 @@ namespace Microsoft.PowerShell.Commands
                     jobAssigned = jobObject.AssignProcessToJobObject(processInfo.Process);
                 }
 
+                // Since the process wasn't spawned by .NET, we need to trigger .NET to get a lock on the handle of the process.
+                // Otherwise, accessing properties like `ExitCode` will throw the following exception:
+                //   "Process was not started by this object, so requested information cannot be determined."
+                // Fetching the process handle will trigger the `Process` object to update its internal state by calling `SetProcessHandle`,
+                // the result is discarded as it's not used later in this code.
+                _ = process.Handle;
+
                 // Resume the process now that is has been set up.
                 processInfo.Resume();
 #endif

test/powershell/Modules/Microsoft.PowerShell.Management/Start-Process.Tests.ps1

@@ -115,6 +115,11 @@ Describe "Start-Process" -Tag "Feature","RequireAdminOnWindows" {
         { Start-Process -FilePath $pingCommand -NoNewWindow -WindowStyle Normal -ErrorAction Stop } | Should -Throw -ErrorId "InvalidOperationException,Microsoft.PowerShell.Commands.StartProcessCommand"
     }
 
+    It "ExitCode returns with -NoNewWindow, -PassThru and -Wait" {
+        $process = Start-Process -FilePath $pingCommand -ArgumentList $pingParam -NoNewWindow -PassThru -Wait -ErrorAction Stop
+        $process.ExitCode | Should -Be 0
+    }
+
     It "Should start cmd.exe with Verb 'open' and WindowStyle 'Minimized'" -Skip:(!$isFullWin) {
         $fileToWrite = Join-Path $TestDrive "VerbTest.txt"
         $process = Start-Process cmd.exe -ArgumentList "/c echo abc > $fileToWrite" -Verb open -WindowStyle Minimized -PassThru