Missing terminal output when scrolling up

[mattacosta]

Issue Type: Bug

Steps to reproduce:

1. Run a simple script in the terminal a few times.
   Ex: console.log('Hello world');
2. Scroll up.
3. For previously hidden output, one of the first few lines is now missing.

Notes:

• I have no custom terminal settings.
• If the output has more than 1 line, subsequent lines are shown.

VS Code version: Code - Insiders 1.43.0-insider (b0be067, 2020-02-26T05:30:24.470Z)
OS version: Windows_NT x64 10.0.18362

Extensions (2)

Extension	Author (truncated)	Version
vscode-eslint	dba	2.1.1
vscode-icon-theme	jtl	1.6.5

[Tyriar]

By first line do you mean at the top or bottom? A gif would be helpful to see if a line is going missing.

[mattacosta]

After more testing... I don't even know what's going on anymore:

console.log('1');
console.log('2');
console.log('3');  // <-- missing

console.log('1');
console.log('2');  // <-- missing
console.log('3');
console.log('4');

Tests:

• 2 lines: the line with "2" went missing
• 3 lines: the line with "3" went missing - see gif above
• 4 lines: the line with "2" went missing - see gif above
• 5 lines: the line with "5" went missing
• 6 lines: the line with "1" went missing

When the gif loops, you can also see that a line from the Windows PowerShell header is missing too.

[Tyriar]

Unconfirmed, likely an upstream problem.

[ALapinskas]

Have same behavior. It is repeated only when you choose powershell, cmd works fine. Howewer it is not repeated from powershell started as standalone application. The version of powershell is 5.1.18362.628, located under C:\Windows\System32\WindowsPowerShell\v1.0

[jppm99]

Disabling conPTY fixed this for me.

[mattacosta]

Did more digging and this looks very similar to: microsoft/terminal#3163

That in turn links to PowerShell/PSReadLine#724 which was fixed a little over a year ago. As far as I can tell, my system already has the latest version (2.0.0) of this module though...

[Tyriar]

Nothing we can do here on our side, see linked issues