F# interactive shows random characters when editing a line

[egamma]

From @basvdlinden on December 19, 2016 20:34

• VSCode Version: Code 1.8.0 (38746938a4ab94f2f57d9e1309c51fd6fb37553d, 2016-12-13T17:45:32.595Z)
• OS Version: Windows_NT ia32 10.0.14393
• Extensions:

Extension	Author	Version
Ionide-fsharp	Ionide	2.13.2
csharp	ms-vscode	1.5.3

---

Steps to Reproduce:

1. Type a few characters
2. Press backspace a few times

or

1. Type a few characters
2. Use mouse to select a character in the middle
3. Type a few characters

Copied from original issue: microsoft/vscode#17557

[Krzysztof-Cieslak]

@egamma F# Interactive is using terminal integration (createTerminal with shellPath set to fsi.exe) so as far as I understand Ionide shouldn't have any impact on stuff that happens when user is typing in directly in it.

IMO either:

1. It's bug in Code's terminal (and this should be reproducible with normal terminal, not only FSI -@basvdlinden, please try that)
2. It's bug in F# Interactive (and then it should be reproducible outside of VSCode, using FSI in command line - again, @basvdlinden, please try that)

[egamma]

@Krzysztof-Cieslak agreed, if this can be reproduced outside of the F# interactive, then please move the issue back to vscode.

[basvdlinden]

Test executed. Number 3 and 5 resulted in the same behavior:

1. Use "C:\Program Files (x86)\Microsoft SDKs\F#\4.0\Framework\v4.0\Fsi.exe" outside VSCode: No random characters. Can't reproduce the problem.
2. Use normal terminal (cmd.exe) from VSCode terminal: No random characters. Can't reproduce the problem.
3. Use normal terminal (cmd.exe) from VSCode terminal AND then start FSI.exe. "C:\Program Files (x86)\Microsoft SDKs\F#\4.0\Framework\v4.0\Fsi.exe". Random characters. I can reproduce same behavior as using "ALT Enter" and then editing line.
4. Use powershell terminal ("terminal.integrated.shell.windows": "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe") from VSCode terminal. No random characters. Can't reproduce the problem.
5. Use powershellterminal ("terminal.integrated.shell.windows": "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe") from VSCode terminal AND then start FSI.exe. "C:\Program Files (x86)\Microsoft SDKs\F#\4.0\Framework\v4.0\Fsi.exe". Random characters. I can reproduce same behavior as using "ALT Enter" and then editing line.
6. Run cmd.exe and then "C:\Program Files (x86)\Microsoft SDKs\F#\4.0\Framework\v4.0\Fsi.exe" outside VSCode: No random characters. Can't reproduce the problem.

---

I updated before testing:

• VSCode Version: Code 1.8.1 (ee428b0eead68bf0fb99ab5fdc4439be227b6281, 2016-12-19T14:49:23.350Z)
• OS Version: Windows_NT ia32 10.0.14393
• Extensions:

Extension	Author	Version
Ionide-fsharp	Ionide	2.15.0
csharp	ms-vscode	1.5.3

[basvdlinden]

Retested. Same behavior for extensions:

Extension	Author	Version
Ionide-fsharp	Ionide	2.19.4
csharp	ms-vscode	1.6.2

[egamma]

@basvdlinden I cannot reproduce the behaviour given the above steps in the latest insider version. Please see the attached recording.

Can you pls try to reproduce in the insider build as well https://code.visualstudio.com/insiders

[basvdlinden]

@egamma I can reproduce it doing exactly the same. (Although reproducing it with just 10 characters on one line may take a few retries)

I have a different F# interactive version ...

Microsoft (R) F# Interactive version 14.0.23413.0
Copyright (c) Microsoft Corporation. All Rights Reserved.

For help type #help;;

I have also installed VS2015 update 3 on my system (and the Visual F# 4.0 extension)

[egamma]

@basvdlinden can you please add an animated gif. This will help with coming up with a repro.

// FYI @Tyriar

[Tyriar]

If this is about the prompt going out of sync with the backend after pressing backspace I expect it to be fixed in v1.9 as part of the winpty upgrade. See microsoft/vscode#14613 and microsoft/vscode#7345

[basvdlinden]

FSI works, but VSCODE has the problem:

[Tyriar]

@basvdlinden that's the stable build (1.8.1). Can you test on Insiders (1.9.0)?

[basvdlinden]

Could not reproduce the problem with VSCODE insiders.

(What you can't see on the animated gif is that the cursor jumps to random locations, within the input string, for a very short time on ever backspace key input.)

[egamma]

Closing - works in insiders build and will be pushed to stable soon.