PowerShell Snippet adds unwanted Backslash Character to Prompt

[KenADev]

In the section PowerShell: powershell.exe or pwsh.exe, this code snippet is shown:

function prompt {
  $loc = $($executionContext.SessionState.Path.CurrentLocation);
  $out = "PS $loc$('>' * ($nestedPromptLevel + 1)) ";
  $out += "$([char]27)]9;9;`"$loc`"$([char]27)\"
  return $out
}

When I put it in my PowerShell Profile and open a new PowerShell window, an unwanted backslash character is added to the command prompt when typing. (In pure PowerShell and also in Windows Terminal)
It is shown, but not interpreted.

Example:
PS C:\Users\xxx\somedir>\$x=

The backslash appears as soon as the equal sign is typed, but also (seemingly) randomly.
I first thought the backslash in this line was at fault, but removing it causes an exception:
$out += "$([char]27)]9;9;`"$loc`"$([char]27)\"

Last 4 keys:
 e Backspace d o

Exception:
System.ArgumentOutOfRangeException: StartIndex must not be lower than zero
Parametername: startIndex
   bei System.String.Substring(Int32 startIndex, Int32 length)
   bei Microsoft.PowerShell.PSConsoleReadLine.ReallyRender(RenderData renderData, String defaultColor)
   bei Microsoft.PowerShell.PSConsoleReadLine.ForceRender()
   bei Microsoft.PowerShell.PSConsoleReadLine.Insert(Char c)
   bei Microsoft.PowerShell.PSConsoleReadLine.SelfInsert(Nullable`1 key, Object arg)
   bei Microsoft.PowerShell.PSConsoleReadLine.ProcessOneKey(ConsoleKeyInfo key, Dictionary`2 dispatchTable, Boolean ignoreIfNoAction, Object arg)
   bei Microsoft.PowerShell.PSConsoleReadLine.InputLoop()
   bei Microsoft.PowerShell.PSConsoleReadLine.ReadLine(Runspace runspace, EngineIntrinsics engineIntrinsics)

Windows Terminal Version: 1.15.2712.0
$PSVersionTable:

Name                           Value
----                           -----
PSVersion                      5.1.19041.1682
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.19041.1682
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
---

Document Details

⚠ Do not edit this section. It is required for learn.microsoft.com ➟ GitHub issue linking.

• ID: 439baddf-3ec9-a46e-1b6e-3ec47cbd1d4c
• Version Independent ID: 439baddf-3ec9-a46e-1b6e-3ec47cbd1d4c
• Content: Opening a tab/pane in the same directory
• Content Source: TerminalDocs/tutorials/new-tab-same-directory.md
• Product: dev-environment
• Technology: windows-terminal
• GitHub Login: @zadjii-msft
• Microsoft Alias: migrie

[mattwojo]

Hmm... this is a weird issue. @zadjii-msft -- any thoughts?

[zadjii-msft]

Yea I need to update that snippet. Clearly, I don't use pwsh as my daily driver.

I have a much more elaborate pwsh prompt I've been testing lately. I need to take this, and boil it down:

  $loc = $($executionContext.SessionState.Path.CurrentLocation);
  # IMPORTANT: Make sure there's a printable charater _last_ in the prompt.
  # Otherwise, PSReadline is gonna use the terminating `\` here and colorize
  # that if it detects a syntax error
  $out += "`e]133;A$([char]07)";
  $out += "`e]9;9;`"$loc`"$([char]07)";
  $out += "PWSH $loc$('>' * ($nestedPromptLevel + 1)) ";
  $out += "`e]133;B$([char]07)";

  $Global:__LastHistoryId = $LastHistoryEntry.Id

  return $out
  

All the e]133; sequences are prompt markup sequences which aren't released yet, but the 9;9 stuff should be relevant

[mattwojo]

@zadjii-msft - Just wondering about this snippet issue... should I update the doc with your code above? Or have you had a chance to try boiling it down? Would love to get this resolved when you have a spare moment.

[yan12125]

This looks like a PowerShell issue, as I can reproduce it even on Linux (Konsole). See PowerShell/PSReadLine#3719.