Make Out-String and Out-File keep string input unchanged (#17455)

src/System.Management.Automation/FormatAndOutput/common/BaseOutputtingCommand.cs

@@ -552,7 +552,8 @@ namespace Microsoft.PowerShell.Commands.Internal.Format
                 }
                 else
                 {
-                    _lo.WriteLine(rte.text);
+                    // Write out raw text without any changes to it.
+                    _lo.WriteRawText(rte.text);
                 }
 
                 return;

src/System.Management.Automation/FormatAndOutput/common/ILineOutput.cs

@@ -250,6 +250,13 @@ namespace Microsoft.PowerShell.Commands.Internal.Format
         /// </param>
         internal abstract void WriteLine(string s);
 
+        /// <summary>
+        /// Write a line of string as raw text to the output device, with no change to the string.
+        /// For example, keeping VT escape sequences intact in it.
+        /// </summary>
+        /// <param name="s">The raw text to be written to the device.</param>
+        internal virtual void WriteRawText(string s) => WriteLine(s);
+
         internal WriteStreamType WriteStream
         {
             get;
@@ -431,7 +438,7 @@ namespace Microsoft.PowerShell.Commands.Internal.Format
     /// Implementation of the ILineOutput interface accepting an instance of a
     /// TextWriter abstract class.
     /// </summary>
-    internal class TextWriterLineOutput : LineOutput
+    internal sealed class TextWriterLineOutput : LineOutput
     {
         #region ILineOutput methods
 
@@ -467,9 +474,17 @@ namespace Microsoft.PowerShell.Commands.Internal.Format
         /// <param name="s"></param>
         internal override void WriteLine(string s)
         {
-            CheckStopProcessing();
+            WriteRawText(PSHostUserInterface.GetOutputString(s, isHost: false));
+        }
 
-            s = PSHostUserInterface.GetOutputString(s, isHost: false);
+        /// <summary>
+        /// Write a raw text by delegating to the writer underneath, with no change to the text.
+        /// For example, keeping VT escape sequences intact in it.
+        /// </summary>
+        /// <param name="s">The raw text to be written to the device.</param>
+        internal override void WriteRawText(string s)
+        {
+            CheckStopProcessing();
 
             if (_suppressNewline)
             {
@@ -480,6 +495,7 @@ namespace Microsoft.PowerShell.Commands.Internal.Format
                 _writer.WriteLine(s);
             }
         }
+
         #endregion
 
         /// <summary>

test/powershell/engine/Formatting/ErrorView.Tests.ps1

@@ -115,7 +115,8 @@ Describe 'Tests for $ErrorView' -Tag CI {
 
         It "Error shows for advanced function" {
             # need to have it virtually interactive so that InvocationInfo.MyCommand is empty
-            $e = '[cmdletbinding()]param()$pscmdlet.writeerror([System.Management.Automation.ErrorRecord]::new(([System.NotImplementedException]::new("myTest")),"stub","notimplemented","command"))' | pwsh -noprofile -file - 2>&1 | Out-String
+            $e = '[cmdletbinding()]param()$pscmdlet.writeerror([System.Management.Automation.ErrorRecord]::new(([System.NotImplementedException]::new("myTest")),"stub","notimplemented","command"))' | pwsh -noprofile -file - 2>&1
+            $e = $e | Where-Object { $_ -is [System.Management.Automation.ErrorRecord] } | Out-String
             $e | Should -Not -BeNullOrEmpty
 
             # need to see if ANSI escape sequences are in the output as ANSI is disabled for CI

test/powershell/engine/Formatting/OutputRendering.Tests.ps1

@@ -39,7 +39,7 @@ Describe 'OutputRendering tests' {
         param($outputRendering, $ansi)
 
         $PSStyle.OutputRendering = $outputRendering
-        $out = "$($PSStyle.Foreground.Green)hello" | Out-String
+        $out = [pscustomobject] @{ key = "$($PSStyle.Foreground.Green)hello" } | Out-String
 
         if ($ansi) {
             $out | Should -BeLike "*`e*" -Because ($out | Format-Hex | Out-String)

test/powershell/engine/Formatting/PSStyle.Tests.ps1

@@ -286,6 +286,77 @@ Describe 'Tests for $PSStyle automatic variable' {
         $strDec.ContentLength | Should -Be $word.Length
         $strDec.ToString("PlainText") | Should -Be $word
     }
+
+    It "String intput to Out-String should be intact with OutputRendering='<OutputRendering>'" -TestCases @(
+        @{ OutputRendering = 'Ansi'; ContainsAnsi = $true }
+        @{ OutputRendering = 'Host'; ContainsAnsi = $false }
+        @{ OutputRendering = 'PlainText'; ContainsAnsi = $false }
+    ) {
+        param($OutputRendering, $ContainsAnsi)
+
+        $oldRender = $PSStyle.OutputRendering
+        $testStr = "`e[31mABC`e[0m"
+
+        try {
+            $PSStyle.OutputRendering = $OutputRendering
+            ## For input that actually goes through formatting, Out-String should remove VT sequences
+            ## from the formatting output based on the output rendering option that is in effect.
+            (Get-Verb -Verb Get | Out-String).Contains("`e[") | Should -Be $ContainsAnsi
+            ## For string input, since no formatting is applied, Out-String should keep the string intact.
+            ($testStr | Out-String).Trim() | Should -BeExactly $testStr
+        }
+        finally {
+            $PSStyle.OutputRendering = $oldRender
+        }
+    }
+
+    It "String input to Out-File should be intact with OutputRendering='<OutputRendering>'" -TestCases @(
+        @{ OutputRendering = 'Ansi'; }
+        @{ OutputRendering = 'Host'; }
+        @{ OutputRendering = 'PlainText'; }
+    ) {
+        param($OutputRendering)
+
+        $oldRender = $PSStyle.OutputRendering
+        $content = "Read-Host -Prompt '`e[33mEnter your device code`e[0m'"
+        Set-Content -Path $TestDrive\test.ps1 -Value $content -Encoding utf8NoBOM
+
+        try {
+            $PSStyle.OutputRendering = $OutputRendering
+            Get-Content $TestDrive\test.ps1 > $TestDrive\copy.ps1
+            (Get-Content $TestDrive\copy.ps1 -Raw).Trim() | Should -BeExactly $content
+        }
+        finally {
+            $PSStyle.OutputRendering = $oldRender
+            Remove-Item $TestDrive\test.ps1 -Force
+            Remove-Item $TestDrive\copy.ps1 -Force
+        }
+    }
+
+    It "Comment based help works with `$PSStyle when OutputRendering='<OutputRendering>'" -TestCases @(
+        @{ OutputRendering = 'Ansi'; ContainsAnsi = $true }
+        @{ OutputRendering = 'Host'; ContainsAnsi = $false }
+        @{ OutputRendering = 'PlainText'; ContainsAnsi = $false }
+    ) {
+        param($OutputRendering, $ContainsAnsi)
+
+        $oldRender = $PSStyle.OutputRendering
+
+        function Test-PSStyle {
+            <#
+            .Description
+            Get-Function displays the name and syntax of all functions in the session.
+            #>
+        }
+
+        try {
+            $PSStyle.OutputRendering = $OutputRendering
+            (Get-Help Test-PSStyle | Out-String).Contains("`e[31mdisplays`e[0m") | Should -Be $ContainsAnsi
+        }
+        finally {
+            $PSStyle.OutputRendering = $oldRender
+        }
+    }
 }
 
 Describe 'Handle strings with escape sequences in formatting' {