Backport PR #51558: Fix VS2022 rejecting preview SDKs

Co-authored-by: nagilson <23152278+nagilson@users.noreply.github.com>

Author: Copilot

build/RunTestsOnHelix.cmd

@@ -10,6 +10,9 @@ set PATH=%DOTNET_ROOT%;%PATH%
 set DOTNET_MULTILEVEL_LOOKUP=0
 set TestFullMSBuild=%1
 
+REM Ensure Visual Studio instances allow preview SDKs
+PowerShell -ExecutionPolicy ByPass -NoProfile -File "%HELIX_CORRELATION_PAYLOAD%\t\eng\enable-preview-sdks.ps1"
+
 set TestExecutionDirectory=%CD%\testExecutionDirectory
 mkdir %TestExecutionDirectory%
 

eng/common/tools.ps1

@@ -296,7 +296,7 @@ function InstallDotNet([string] $dotnetRoot,
     if ($runtime -eq "aspnetcore") { $runtimePath = $runtimePath + "\Microsoft.AspNetCore.App" }
     if ($runtime -eq "windowsdesktop") { $runtimePath = $runtimePath + "\Microsoft.WindowsDesktop.App" }
     $runtimePath = $runtimePath + "\" + $version
-  
+
     $dotnetVersionLabel = "runtime toolset '$runtime/$architecture v$version'"
 
     if (Test-Path $runtimePath) {
@@ -545,19 +545,25 @@ function LocateVisualStudio([object]$vsRequirements = $null){
     })
   }
 
-  if (!$vsRequirements) { $vsRequirements = $GlobalJson.tools.vs }
+  if (!$vsRequirements) {
+    if (Get-Member -InputObject $GlobalJson.tools -Name 'vs' -ErrorAction SilentlyContinue) {
+      $vsRequirements = $GlobalJson.tools.vs
+    } else {
+      $vsRequirements = $null
+    }
+  }
   $args = @('-latest', '-format', 'json', '-requires', 'Microsoft.Component.MSBuild', '-products', '*')
 
   if (!$excludePrereleaseVS) {
     $args += '-prerelease'
   }
 
-  if (Get-Member -InputObject $vsRequirements -Name 'version') {
+  if ($vsRequirements -and (Get-Member -InputObject $vsRequirements -Name 'version' -ErrorAction SilentlyContinue)) {
     $args += '-version'
     $args += $vsRequirements.version
   }
 
-  if (Get-Member -InputObject $vsRequirements -Name 'components') {
+  if ($vsRequirements -and (Get-Member -InputObject $vsRequirements -Name 'components' -ErrorAction SilentlyContinue)) {
     foreach ($component in $vsRequirements.components) {
       $args += '-requires'
       $args += $component

eng/enable-preview-sdks.ps1

@@ -0,0 +1,59 @@
+param()
+
+. $PSScriptRoot\common\tools.ps1
+
+try {
+    $vsInfo = LocateVisualStudio
+}
+catch {
+    Write-Host "LocateVisualStudio failed: $_"
+    return
+}
+
+if ($null -eq $vsInfo) {
+    Write-Host "No Visual Studio instance detected; preview SDKs remain enabled by default."
+    return
+}
+
+$vsId = $vsInfo.instanceId
+$vsMajorVersion = $vsInfo.installationVersion.Split('.')[0]
+$instanceDir = Join-Path $env:USERPROFILE "AppData\Local\Microsoft\VisualStudio\$vsMajorVersion.0_$vsId"
+
+Create-Directory $instanceDir
+
+$sdkFile = Join-Path $instanceDir 'sdk.txt'
+
+$desiredLine = 'UsePreviews=True'
+$existingLines = @()
+
+if (Test-Path $sdkFile) {
+    $existingLines = @(Get-Content -Path $sdkFile -Encoding ASCII)
+}
+
+# Determine how to place the UsePreviews flag based on existing content.
+$replacementIndex = -1
+for ($i = 0; $i -lt $existingLines.Count; $i++) {
+    if ($existingLines[$i] -match '^UsePreviews=.*$') {
+        $replacementIndex = $i
+        break
+    }
+}
+
+# Replace the existing line to enforce it as True
+if ($replacementIndex -ge 0) {
+    $updatedLines = $existingLines
+    $updatedLines[$replacementIndex] = $desiredLine
+}
+elseif ($existingLines.Count -gt 0) {
+    # Write to the top of the file but keep the remaining portion (assumption: order does not matter to VS)
+    $updatedLines = @($desiredLine) + $existingLines
+}
+else {
+    # Write a whole new file
+    $updatedLines = @($desiredLine)
+}
+
+Set-Content -Path $sdkFile -Value $updatedLines -Encoding ASCII
+
+Write-Host "Updated $sdkFile"
+Get-Content -Path $sdkFile | ForEach-Object { Write-Host "  $_" }