Wrap $PSProcessPath automatic variable in PSProcessPathAutomaticVariable experimental feature

src/System.Management.Automation/engine/ExperimentalFeature/ExperimentalFeature.cs

@@ -22,6 +22,7 @@ public class ExperimentalFeature
         internal const string EngineSource = "PSEngine";
         internal const string PSSerializeJSONLongEnumAsNumber = nameof(PSSerializeJSONLongEnumAsNumber);
         internal const string PSProfileDSCResource = "PSProfileDSCResource";
+        internal const string PSProcessPathAutomaticVariable = "PSProcessPathAutomaticVariable";
 
         #endregion
 
@@ -114,6 +115,10 @@ static ExperimentalFeature()
                 new ExperimentalFeature(
                     name: PSProfileDSCResource,
                     description: "DSC v3 resources for managing PowerShell profile."
+                ),
+                new ExperimentalFeature(
+                    name: PSProcessPathAutomaticVariable,
+                    description: "Adds the $PSProcessPath automatic variable containing the path to the current PowerShell process executable."
                 )
             };
 

src/System.Management.Automation/engine/SessionState.cs

@@ -377,12 +377,15 @@ internal void InitializeFixedVariables()
                                RunspaceInit.EnabledExperimentalFeatures);
             this.GlobalScope.SetVariable(v.Name, v, asValue: false, force: true, this, CommandOrigin.Internal, fastPath: true);
 
-            // $PSProcessPath
-            v = new PSVariable(SpecialVariables.PSProcessPath,
-                               Environment.ProcessPath,
-                               ScopedItemOptions.Constant | ScopedItemOptions.AllScope,
-                               RunspaceInit.PSProcessPathDescription);
-            this.GlobalScope.SetVariable(v.Name, v, asValue: false, force: true, this, CommandOrigin.Internal, fastPath: true);
+            // $PSProcessPath - only registered when the experimental feature is enabled
+            if (ExperimentalFeature.IsEnabled(ExperimentalFeature.PSProcessPathAutomaticVariable))
+            {
+                v = new PSVariable(SpecialVariables.PSProcessPath,
+                                   Environment.ProcessPath,
+                                   ScopedItemOptions.Constant | ScopedItemOptions.AllScope,
+                                   RunspaceInit.PSProcessPathDescription);
+                this.GlobalScope.SetVariable(v.Name, v, asValue: false, force: true, this, CommandOrigin.Internal, fastPath: true);
+            }
         }
 
         /// <summary>

test/powershell/Language/Parser/AutomaticVariables.Tests.ps1

@@ -22,28 +22,71 @@ Describe 'Automatic variable $input' -Tags "CI" {
 }
 
 Describe 'Automatic variable $PSProcessPath' -Tags "CI" {
+    BeforeAll {
+        $script:psProcessPathFeatureEnabled = $EnabledExperimentalFeatures.Contains('PSProcessPathAutomaticVariable')
+        $script:psProcessPathSkipMessage = "The experimental feature 'PSProcessPathAutomaticVariable' must be enabled to use `$PSProcessPath."
+    }
+
     It '$PSProcessPath should return a non-empty string' {
+        if (-not $script:psProcessPathFeatureEnabled) {
+            Set-ItResult -Skipped -Because $script:psProcessPathSkipMessage
+            return
+        }
         $PSProcessPath | Should -Not -BeNullOrEmpty
     }
 
     It '$PSProcessPath should be a string' {
+        if (-not $script:psProcessPathFeatureEnabled) {
+            Set-ItResult -Skipped -Because $script:psProcessPathSkipMessage
+            return
+        }
         $PSProcessPath | Should -BeOfType [string]
     }
 
     It '$PSProcessPath should point to an existing file' {
+        if (-not $script:psProcessPathFeatureEnabled) {
+            Set-ItResult -Skipped -Because $script:psProcessPathSkipMessage
+            return
+        }
         Test-Path -LiteralPath $PSProcessPath -PathType Leaf | Should -BeTrue
     }
 
     It '$PSProcessPath should be a constant variable' {
+        if (-not $script:psProcessPathFeatureEnabled) {
+            Set-ItResult -Skipped -Because $script:psProcessPathSkipMessage
+            return
+        }
         $var = Get-Variable -Name PSProcessPath
         $var.Options | Should -Match 'Constant'
     }
 
     It '$PSProcessPath should be read-only (cannot be overwritten)' {
+        if (-not $script:psProcessPathFeatureEnabled) {
+            Set-ItResult -Skipped -Because $script:psProcessPathSkipMessage
+            return
+        }
         { $PSProcessPath = 'something' } | Should -Throw
     }
 
     It '$PSProcessPath should match the current process path' {
+        if (-not $script:psProcessPathFeatureEnabled) {
+            Set-ItResult -Skipped -Because $script:psProcessPathSkipMessage
+            return
+        }
         $PSProcessPath | Should -Be ([System.Environment]::ProcessPath)
     }
 }
+
+Describe 'Automatic variable $PSProcessPath - feature disabled' -Tags "CI" {
+    BeforeAll {
+        $script:psProcessPathFeatureEnabled = $EnabledExperimentalFeatures.Contains('PSProcessPathAutomaticVariable')
+    }
+
+    It '$PSProcessPath should not exist when experimental feature is disabled' {
+        if ($script:psProcessPathFeatureEnabled) {
+            Set-ItResult -Skipped -Because "The experimental feature 'PSProcessPathAutomaticVariable' is enabled; test requires the feature to be disabled."
+            return
+        }
+        { Get-Variable -Name PSProcessPath -ErrorAction Stop } | Should -Throw
+    }
+}