Skip settings schema validation on PowerShell versions less than 7

Actions/.Modules/ReadSettings.psm1

@@ -595,23 +595,16 @@ function ValidateSettings {
         $settings
     )
     Process {
+        if ($PSVersionTable.PSVersion.Major -lt 7) {
+            return
+        }
+
         $settingsJson = ConvertTo-Json -InputObject $settings -Depth 99 -Compress
         $settingsSchemaFile = Join-Path $PSScriptRoot "settings.schema.json" -Resolve
 
         $result = ""
         try{
-            $command  = [scriptblock] {
-                $result = ''
-                Test-Json -Json $args[0] -SchemaFile $args[1] -ErrorVariable result -ErrorAction SilentlyContinue | Out-Null
-                return $result
-            }
-
-            if($PSVersionTable.PSVersion.Major -lt 6) { # Test-Json is not available in PS5.1
-                $result = pwsh -noprofile -Command $command -args $settingsJson, $settingsSchemaFile
-            }
-            else {
-                $result = Invoke-Command -ScriptBlock $command -ArgumentList $settingsJson, $settingsSchemaFile
-            }
+            Test-Json -Json $settingsJson -SchemaFile $settingsSchemaFile -ErrorVariable result -ErrorAction SilentlyContinue | Out-Null
         }
         catch {
             OutputWarning "Error validating settings. Error: $($_.Exception.Message)"

RELEASENOTES.md

@@ -45,6 +45,7 @@ The `DownloadProjectDependencies` action now downloads only artifacts from depen
 - Issue 2204 - Workspace compilation ignores vsixFile setting
 - Issue 2211 - Cannot create a release if a project contains only test apps
 - Issue 2214 - Workspace compilation not working with external dependencies
+- Fix "filename or extension is too long" error when validating settings on PS5.1 with large settings JSON
 - Issue 2235 - Workspace compilation: only the first `customCodeCops` entry resolved when multiple relative paths were configured. Relative `customCodeCops` paths are now resolved against the project folder before being passed to the compiler.
 
 ## v9.0

Tests/ReadSettings.Test.ps1

@@ -540,5 +540,28 @@ InModuleScope ReadSettings { # Allows testing of private functions
             Pop-Location
             Remove-Item -Path $tempName -Recurse -Force
         }
+
+        It 'ValidateSettings skips validation entirely on PS versions less than 7 without warning' {
+            Mock OutputWarning { }
+
+            $settings = @{ "someProp" = "someValue" }
+
+            if ($PSVersionTable.PSVersion.Major -ge 7) {
+                # On PS7+, the Invoke-Command path is used in-process.
+                ValidateSettings -settings $settings
+            }
+            else {
+                # On PS < 7, validation is skipped entirely; pwsh should never be called
+                Mock pwsh { throw "pwsh should not be called on PS < 7" }
+
+                ValidateSettings -settings $settings
+
+                # Verify pwsh was NOT called
+                Should -Invoke -CommandName pwsh -Times 0
+            }
+
+            # Verify no warning was output
+            Should -Invoke -CommandName OutputWarning -Times 0
+        }
     }
 }