PSReadline char @ is added in the output of all scripts

[PrzemyslawKlys]

Issue Description

I am experiencing a problem with PSReadline random chars being added to the output of all scripts.

After the script is done, press ENTER and it shows the error as above.

Attached Logs

Follow the instructions in the README about
capturing and sending logs.

Environment Information

Visual Studio Code

Name	Version
Operating System	Windows_NT x64 10.0.17763
VSCode	1.39.2
PowerShell Extension Version	2019.11.0

PowerShell Information

Name	Value
PSVersion	5.1.17763.771
PSEdition	Desktop
PSCompatibleVersions	1.0 2.0 3.0 4.0 5.0 5.1.17763.771
BuildVersion	10.0.17763.771
CLRVersion	4.0.30319.42000
WSManStackVersion	3.0
PSRemotingProtocolVersion	2.3
SerializationVersion	1.1.0.1

Visual Studio Code Extensions

Visual Studio Code Extensions(Click to Expand)

Extension	Author	Version
beautify	HookyQR	1.5.0
gitlens	eamodio	10.1.1
material-icon-theme	PKief	3.9.1
open-in-browser	techer	2.0.0
powershell-preview	ms-vscode	2019.11.0
theme-monokai-pro-vscode	monokai	1.1.14
vscode-wakatime	WakaTime	2.2.1

[bgelens]

I have a similar thing. F8 for run selection will insert @ on the new prompt after running the selection

$PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.0.0-preview.5
PSEdition                      Core
GitCommitId                    7.0.0-preview.5
OS                             Darwin 19.0.0 Darwin Kernel Version 19.0.0: Thu Oct 17 16:17:15 PDT 2019; root:xnu-6153.41.3~29/RELEASE_X86_64
Platform                       Unix
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

[TylerLeonhardt]

Yes this seems to be an issue in PSReadLine. I'm investigating it and can repro

[TylerLeonhardt]

Thankfully, the @ in the prompt does not impact F8'ing code so you can still do that even if there's a @ (or anything really) sitting in your prompt

[bgelens]

True. They do stack up though :)

[TylerLeonhardt]

This was introduced in PowerShell/PowerShellEditorServices#1072

What's the saying? "1 bug fixed, 2 more appear"? 😅

[rjmholt]

/cc @daxian-dbw

[rjmholt]

So I've done some debugging here and it looks like our API with PSReadLine isn't quite right.

Here is where we implement our own version of Console.ReadLine() which we can cancel so as to run PowerShell commands for things like completions in the background.

Currently, when it cancels, it sends back default(ConsoleKeyInfo) to PSReadLine. This is effectively as NUL char ('\0'). I suspect that either PSReadLine or xtermjs turns that into an @.

I played with turning it into a space, returning new ConsoleKeyInfo(' ', ConsoleKey.Spacebar, shift: false, alt: false, control: false). It's not perfect, but it's a lot less problematic than @.

Short term, we should find a character that is as helpful as possible that we can return here.

Medium term, we should work with @daxian-dbw to change the way we interact with PSReadLine either to make this bool TryReadKey(out ConsoleKeyInfo cki) (or with a nullable), or look into idle eventing (@daxian-dbw's suggestion) for running commands behind the prompt.

[rjmholt]

Give this VSIX a try and let me know if it solves things. @PrzemyslawKlys I'm particularly interested in whether it solves any of your other bugs.

psvsix.zip