Reject ampersand-separated DSC resource bodies (#2288)

* Initial plan

* Reject ampersand-separated DSC body pairing

Co-authored-by: bergmeister <9250262+bergmeister@users.noreply.github.com>

* Fix DSC separator detection across PowerShell versions

Co-authored-by: bergmeister <9250262+bergmeister@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: bergmeister <9250262+bergmeister@users.noreply.github.com>

Author: Copilot

Rules/AvoidAlias.cs

@@ -348,7 +348,7 @@ private ScriptBlockExpressionAst GetDscResourceBody(CommandAst cmdAst)
                         && bodyPipeline.PipelineElements.Count == 1
                         && bodyPipeline.PipelineElements[0] is CommandExpressionAst bodyExpression)
                     {
-                        if (HasSemicolonSeparator(pipeline, bodyPipeline)
+                        if (HasStatementSeparator(cmdAst, bodyPipeline)
                             || bodyExpression.Redirections.Count != 0)
                         {
                             return null;
@@ -364,9 +364,9 @@ private ScriptBlockExpressionAst GetDscResourceBody(CommandAst cmdAst)
             return null;
         }
 
-        private bool HasSemicolonSeparator(Ast statement, Ast nextStatement)
+        private bool HasStatementSeparator(CommandAst statement, Ast nextStatement)
         {
-            int separatorStart = statement.Extent.EndOffset;
+            int separatorStart = statement.CommandElements[statement.CommandElements.Count - 1].Extent.EndOffset;
             int separatorLength = nextStatement.Extent.StartOffset - separatorStart;
             if (separatorLength <= 0)
             {
@@ -375,13 +375,13 @@ private bool HasSemicolonSeparator(Ast statement, Ast nextStatement)
 
             string script = statement.Extent.EndScriptPosition.GetFullScript();
             string separator = script.Substring(separatorStart, separatorLength);
-            if (separator.IndexOf(';') < 0)
+            if (separator.IndexOf(';') < 0 && separator.IndexOf('&') < 0)
             {
                 return false;
             }
 
             Parser.ParseInput(separator, out Token[] tokens, out ParseError[] errors);
-            return tokens.Any(token => token.Kind == TokenKind.Semi);
+            return tokens.Any(token => token.Kind == TokenKind.Semi || token.Kind == TokenKind.Ampersand);
         }
 
         /// <summary>

Tests/Rules/AvoidUsingAlias.tests.ps1

@@ -233,12 +233,14 @@ Configuration PackageTest {
             }
         }
 
-        It "does not pair following-line blocks with commands when the block has redirections or a statement terminator intervenes" {
+        It "does not pair following-line blocks with commands when the block has redirections or a statement separator intervenes" {
             $target = @'
 {
     gci .
     {} > $null
     gci .; {}
+    gci . &
+    {}
 }
 '@
             $ast = [System.Management.Automation.Language.Parser]::ParseInput($target, [ref]$null, [ref]$null)
@@ -250,7 +252,7 @@ Configuration PackageTest {
 
             $violations = @($rule.AnalyzeScript($configuration, $null))
 
-            $violations.Count | Should -Be 2
+            $violations.Count | Should -Be 3
             $violations | ForEach-Object {
                 $_.Extent.Text | Should -Be 'gci'
                 $_.SuggestedCorrections[0].Text | Should -Be 'Get-ChildItem'