Try fixing rejection of preview SDK

build/RunTestsOnHelix.cmd

@@ -6,10 +6,15 @@ set NUGET_EXPERIMENTAL_NETWORK_RETRY_DELAY_MILLISECONDS=1000
 
 set MicrosoftNETBuildExtensionsTargets=%HELIX_CORRELATION_PAYLOAD%\ex\msbuildExtensions\Microsoft\Microsoft.NET.Build.Extensions\Microsoft.NET.Build.Extensions.targets
 set DOTNET_ROOT=%HELIX_CORRELATION_PAYLOAD%\d
+set DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR=%HELIX_CORRELATION_PAYLOAD%\r
+set MSBuildSDKsPath=%HELIX_CORRELATION_PAYLOAD%\r
 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\EnablePreviewSdks.ps1"
+
 REM Use powershell to call partical Arcade logic to get full framework msbuild path and assign it
 if "%TestFullMSBuild%"=="true" (
     FOR /F "tokens=*" %%g IN ('PowerShell -ExecutionPolicy ByPass -File "%HELIX_CORRELATION_PAYLOAD%\t\eng\print-full-msbuild-path.ps1"') do (SET DOTNET_SDK_TEST_MSBUILD_PATH=%%g)

build/sdktests.ps1

@@ -7,7 +7,7 @@ Param(
     [string] $tests = "",
     [Parameter(ValueFromRemainingArguments=$true)][String[]]$additionalRunParams
 )
-
+EnablePreviewSdks
 Set-StrictMode -Version 2.0
 $ErrorActionPreference = "Stop"
 
@@ -52,7 +52,7 @@ if ($run)
     foreach ( $name in $testNames )
     {
         $cmd = "testSdk$name"
-        
+
         & $cmd -xml ($name + "results.xml") $additionalRunParams
 
         if ($LASTEXITCODE -ne 0)

eng/EnablePreviewSdks.ps1

@@ -0,0 +1,33 @@
+param()
+
+$RepoRoot = Split-Path -Parent $PSScriptRoot
+if (-not $RepoRoot) {
+    throw "Unable to determine repository root."
+}
+
+. "$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'
+'UsePreviews=True' | Set-Content -Path $sdkFile -Encoding ASCII
+
+Write-Host "Updated $sdkFile"
+Get-Content -Path $sdkFile | ForEach-Object { Write-Host "  $_" }

eng/common/tools.ps1

@@ -295,7 +295,7 @@ 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 $runtimePath) {
@@ -547,19 +547,25 @@ function LocateVisualStudio([object]$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 += $component
@@ -576,6 +582,22 @@ function LocateVisualStudio([object]$vsRequirements = $null){
   return $vsInfo[0]
 }
 
+function EnablePreviewSdks() {
+    $vsInfo = LocateVisualStudio
+    if ($vsInfo -eq $null) {
+        # Preview SDKs are allowed when no Visual Studio instance is installed
+        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"
+    'UsePreviews=True' | Set-Content $sdkFile
+}
+
 function InitializeBuildTool() {
   if (Test-Path variable:global:_BuildTool) {
     # If the requested msbuild parameters do not match, clear the cached variables.
@@ -610,7 +632,7 @@ function InitializeBuildTool() {
     } else {
       $initializeBuildToolFramework=$env:_OverrideArcadeInitializeBuildToolFramework
     }
-    
+
     $buildTool = @{ Path = $dotnetPath; Command = 'msbuild'; Tool = 'dotnet'; Framework = $initializeBuildToolFramework }
   } elseif ($msbuildEngine -eq "vs") {
     try {

eng/restore-toolset.ps1

@@ -4,6 +4,8 @@ function InitializeCustomSDKToolset {
      Write-Host "INFO: Tests will run against full MSBuild in $env:DOTNET_SDK_TEST_MSBUILD_PATH"
   }
 
+  EnablePreviewSdks
+
   if (-not $restore) {
     return
   }

global.json

@@ -1,6 +1,9 @@
 {
   "tools": {
     "dotnet": "9.0.111",
+    "sdk": {
+      "allowPrerelease": true
+    },
     "runtimes": {
       "dotnet": [
         "$(VSRedistCommonNetCoreSharedFrameworkx6490PackageVersion)"
@@ -22,4 +25,4 @@
     "Microsoft.Build.NoTargets": "3.7.0",
     "Microsoft.DotNet.CMake.Sdk": "9.0.0-beta.24217.1"
   }
-}
+}