Handle empty formatter replacements in ranges

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

Author: Copilot

Engine/ScriptAnalyzer.cs

@@ -1733,12 +1733,34 @@ private static EditableText Fix(
                     var columnDelta = 0;
                     if (correction.EndLineNumber == range.End.Line)
                     {
-                        var replacementEndColumn = correction.Lines.Last().TrimEnd('\r').Length
-                            + (correction.Lines.Length == 1 ? correction.StartColumnNumber : 1);
+                        var replacementEndColumn = correction.Lines.Length == 0
+                            ? correction.StartColumnNumber
+                            : correction.Lines.Last().TrimEnd('\r').Length
+                                + (correction.Lines.Length == 1 ? correction.StartColumnNumber : 1);
                         columnDelta = replacementEndColumn - correction.EndColumnNumber;
                     }
 
-                    range = new Range(range.Start, range.End.Shift(lineDelta, columnDelta));
+                    var endLine = range.End.Line + lineDelta;
+                    if (correction.Lines.Length == 0 && endLine < range.Start.Line)
+                    {
+                        if (text.LineCount == 0)
+                        {
+                            range = null;
+                        }
+                        else
+                        {
+                            endLine = Math.Min(Math.Max(endLine, 1), text.LineCount);
+                            var endColumn = Math.Min(
+                                Math.Max(range.End.Column + columnDelta, 1),
+                                text.Lines[endLine - 1].Length + 1);
+                            var end = new Position(endLine, endColumn);
+                            range = new Range(end, end);
+                        }
+                    }
+                    else
+                    {
+                        range = new Range(range.Start, range.End.Shift(lineDelta, columnDelta));
+                    }
                 }
             }
 

Tests/Engine/InvokeFormatter.tests.ps1

@@ -82,6 +82,57 @@ function foo {
             Invoke-Formatter -ScriptDefinition $def -Range @(3, 1, 4, 1) | Should -Be $expected
         }
 
+        It "Should track the range when an edit deletes its last line" {
+            $text = New-Object -TypeName "Microsoft.Windows.PowerShell.ScriptAnalyzer.EditableText" -ArgumentList "first`n`nlast"
+            $correctionType = "Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic.CorrectionExtent" -as [type]
+            $correction = [Activator]::CreateInstance(
+                $correctionType,
+                [object[]]@(2, 2, 1, 1, [string[]]@(), $null, $null))
+            $correctionsType = [System.Collections.Generic.List``1].MakeGenericType($correctionType)
+            $corrections = [Activator]::CreateInstance($correctionsType)
+            $corrections.Add($correction)
+            $range = New-Object -TypeName "Microsoft.Windows.PowerShell.ScriptAnalyzer.Range" -ArgumentList 1, 1, 2, 1
+            $arguments = [object[]]@(
+                $text.PSObject.BaseObject,
+                $corrections.PSObject.BaseObject,
+                0,
+                $range.PSObject.BaseObject)
+            $fixMethod = ("Microsoft.Windows.PowerShell.ScriptAnalyzer.ScriptAnalyzer" -as [type]).GetMethod(
+                'Fix',
+                [Reflection.BindingFlags]'NonPublic, Static')
+
+            $fixMethod.Invoke($null, $arguments) | Out-Null
+
+            $text.ToString() | Should -Be "first`nlast"
+            $arguments[3].End.Line | Should -Be 1
+        }
+
+        It "Should collapse the range when an edit deletes all selected lines" {
+            $text = New-Object -TypeName "Microsoft.Windows.PowerShell.ScriptAnalyzer.EditableText" -ArgumentList "first`nlast"
+            $correctionType = "Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic.CorrectionExtent" -as [type]
+            $correction = [Activator]::CreateInstance(
+                $correctionType,
+                [object[]]@(2, 2, 1, 5, [string[]]@(), $null, $null))
+            $correctionsType = [System.Collections.Generic.List``1].MakeGenericType($correctionType)
+            $corrections = [Activator]::CreateInstance($correctionsType)
+            $corrections.Add($correction)
+            $range = New-Object -TypeName "Microsoft.Windows.PowerShell.ScriptAnalyzer.Range" -ArgumentList 2, 1, 2, 5
+            $arguments = [object[]]@(
+                $text.PSObject.BaseObject,
+                $corrections.PSObject.BaseObject,
+                0,
+                $range.PSObject.BaseObject)
+            $fixMethod = ("Microsoft.Windows.PowerShell.ScriptAnalyzer.ScriptAnalyzer" -as [type]).GetMethod(
+                'Fix',
+                [Reflection.BindingFlags]'NonPublic, Static')
+
+            $fixMethod.Invoke($null, $arguments) | Out-Null
+
+            $text.ToString() | Should -Be "first"
+            $arguments[3].Start.Line | Should -Be 1
+            $arguments[3].End.Line | Should -Be 1
+        }
+
         It "Should apply all corrections when earlier fixes expand the selected line" {
             $def = "if(`$a){'x'}`nif(`$b){'y'}"
             $expected = "if(`$a){'x'}`nif (`$b) { 'y' }"