Implement Windows PowerShell downgrade support using msiexec /f flag

Co-authored-by: MariusStorhaug <[email protected]>

Author: Copilot

action.yml

@@ -204,16 +204,41 @@ runs:
           exit 0
         }
 
+        # Check if we need to handle a downgrade scenario
+        $isDowngrade = $false
+        if ($detected -and $detected -ne $env:REQUESTED_VERSION) {
+          try {
+            $detectedVersion = [version]$detected
+            $requestedVersion = [version]$env:REQUESTED_VERSION
+            if ($detectedVersion -gt $requestedVersion) {
+              Write-Host "Downgrade detected: $detected → $($env:REQUESTED_VERSION)"
+              $isDowngrade = $true
+            } else {
+              Write-Host "Upgrade detected: $detected → $($env:REQUESTED_VERSION)"
+            }
+          } catch {
+            Write-Host "Warning: Could not compare versions, proceeding with installation"
+          }
+        }
+
         $msi = "PowerShell-$($env:REQUESTED_VERSION)-win-x64.msi"
         $url = "https://github.com/PowerShell/PowerShell/releases/download/v$($env:REQUESTED_VERSION)/$msi"
         Write-Host "Downloading from: $url"
 
-        Write-Host "Starting installation of PowerShell [$($env:REQUESTED_VERSION)]..."
-
         if (-not (Invoke-WebRequest -Uri $url -OutFile $msi -UseBasicParsing -PassThru)) {
           Write-Host "Error: Failed to download PowerShell package"
           exit 1
         }
-        Start-Process msiexec.exe -ArgumentList '/i', $msi, '/quiet', '/norestart' -Wait
+
+        Write-Host "Starting installation of PowerShell [$($env:REQUESTED_VERSION)]..."
+
+        if ($isDowngrade) {
+          # For downgrades, use force reinstall to overwrite the existing version
+          Write-Host "Using force reinstall for downgrade scenario..."
+          Start-Process msiexec.exe -ArgumentList '/f', $msi, '/quiet', '/norestart' -Wait
+        } else {
+          # For upgrades or fresh installs, use regular install
+          Start-Process msiexec.exe -ArgumentList '/i', $msi, '/quiet', '/norestart' -Wait
+        }
 
         Write-Host "Installation complete. PowerShell [$($env:REQUESTED_VERSION)] is now available."