Empty line before prompt, after using Clear-Host

[brunovieira97]

Environment

PS version: 7.1.2
PSReadline version:
os: 10.0.19041.860 (WinBuild.160101.0800)
PS file version: 7.1.2.0
HostName: ConsoleHost (Windows Terminal)
BufferWidth: 110
BufferHeight: 35

Steps to reproduce

Have a prompt that spans for two lines, like:

bruno@computer in ~
❯

I've tested this on my home directory, where there are enough items for Get-ChildItem output to be vertically bigger than the Terminal's line count.

bruno@computer in ~
❯ Get-ChildItem

# Output

bruno@computer in ~
❯ Get-ChildItem

# Output

bruno@computer in ~
❯ Clear-Host

Expected behavior

Prompt is written to console and there is no scroll bar, like this:

Actual behavior

After two or three Get-ChildItem's (there's no exact count, except that it must be more than 1 time in a row), Clear-Host will add an extra empty line before writing the prompt to console. The cursor position, though, will be on the correct location, meaning that Windows Terminal will display a scrollbar so you can go one line up.

If you drag the scrollbar to the top, this is shown:

• I've tested disabling PSReadLine on current session by running Remove-Module PSReadLine and everything started to work as expected.
• Tested with ConHost, but could not reproduce the error there.
• Tried calling Set-PSReadLineOption -ExtraPromptLineCount 1, with no effect whatsoever on console output

[daxian-dbw]

I cannot reproduce this in both Windows Terminal and Conhost, with a simple 2-line prompt function prompt { "abc`n> " }:

Is the issue related to your specific prompt function?

[iSazonov]

Maybe key is "After two or three Get-ChildItem's (there's no exact count, except that it must be more than 1 time in a row)"

[daxian-dbw]

Still cannot repro "after two or three Get-ChildItem's":

[iSazonov]

I can not repro with Windows Terminal latest preview 1.7.572.0 and Microsoft Windows 10.0.18363

[brunovieira97]

I use Oh-My-Posh and Posh-Git, but that does not seem related to the problem.

Just removed those modules Import statements from my profile, and left just PSReadLine. This is the result:

It appears as the line being left behind is always the first one to be displayed on console's "viewport".

• My prompt has 2 lines height
• My Get-ChildItem output has a height of 43 lines
• My Windows Terminal window allows for exhibition of 35 lines
• When printing the items, Get-ChildItem makes Windows Terminal scroll down 12 lines, making .m2 directory the first item listed
• Whenever the issue occurs (it's not 100% of the time, apparently), it's always .m2 being displayed over the prompt.

[iSazonov]

Could you please start with pwsh -NoProfile and check again?

[brunovieira97]

Just tested with -NoProfile. Here's the result:

As I said, some times it will not happen. It's very, very strange lol

[iSazonov]

Could you please share gcm clear output?
And gcm clear-host -ShowCommandInfo too.

[brunovieira97]

Sorry for the delay! Here it goes:

PS C:\Users\bruno> gcm clear

CommandType     Name                                               Version    Source
-----------     ----                                               -------    ------
Alias           clear -> Clear-Host

PS C:\Users\bruno> gcm clear-host -ShowCommandInfo

Name          : Clear-Host
ModuleName    :
Module        : @{Name=}
CommandType   : Function
Definition    :
                $RawUI = $Host.UI.RawUI
                $RawUI.CursorPosition = @{X=0;Y=0}
                $RawUI.SetBufferContents(
                    @{Top = -1; Bottom = -1; Right = -1; Left = -1},
                    @{Character = ' '; ForegroundColor = $rawui.ForegroundColor; BackgroundColor =
                $rawui.BackgroundColor})
                # .Link
                # https://go.microsoft.com/fwlink/?LinkID=2096480
                # .ExternalHelp System.Management.Automation.dll-help.xml

ParameterSets : {@{Name=__AllParameterSets; IsDefault=False;
                Parameters=System.Management.Automation.PSObject[]}}

[iSazonov]

The cleaning appears to be working correctly. I can only assume that after clearing, a buffer is output to the console (this is not a console buffer, but some other buffer) that contains the first line of the previous output although it should be empty, then the prompt is displayed.

For normal output, rather the last line might get stuck but we see first line. So my guess is that the problem is in the table output code where we delay to collect multiple rows to define the column widths.(Related discussion and link to code PowerShell/PowerShell#4594 (comment) .)

@brunovieira97 Can you repro with ls | ft? If yes, please try ls | ft -AutoSize:$false and share results.