Can't type NUL character in Terminal using a Windows Alt-code

[wyckster]

Issue Type: Bug

I can type a NUL character in telnet from the Windows command console, but not from a vscode terminal window. I often use telnet to test simple TCP socket servers - in this case I'm trying to send a 0x00 byte to a server - a.k.a. in ASCII as NUL. vscode's terminal window disallows me sending the 0x00 byte. Works fine from a normal console window.

Steps to Reproduce:

In spirit, we're going to try to type a NUL character in a terminal using a windows Alt-Code. Check out How to use alt codes if you don't know how to type them. Basically press Alt, then the decimal digits of the byte to send on the numeric keypad then release Alt.

1. In a terminal, type an ASCII NUL character (Alt + NumPad 0 + NumPad 0 + NumPad 0)

This character does not get typed.

I realize this is difficult to observe.

Here's the actual scenario in which I noticed this:

1. launch vscode (Windows 10)
2. open a terminal (Ctrl + Shift + `)
3. run telnet from the command line interface (may require adding telnet from control panel > turn windows features on or off > Telnet Client)
4. open a connection to a server. (I suggest something that lets you see what characters have been transmitted. If not, use wireshark. The actual server isn't part of this bug. Or set up your own mechanism for detecting the NUL character being typed.)
5. Type a NUL ASCII character (Alt + NumPad 0 + NumPad 0 + NumPad 0)

Notice that the NUL is never emitted in the telnet data stream.

Again, this technique for typing a NUL into telnet works fine from a traditional Windows console, but not from a vscode terminal. It should be possible to type a NUL character using this technique in the vscode terminal.

VS Code version: Code 1.55.2 (3c4e3df, 2021-04-13T09:35:57.887Z)
OS version: Windows_NT x64 10.0.19042

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz (8 x 3410)
GPU Status	2d_canvas: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: enabled opengl: enabled_on protected_video_decode: unavailable_off rasterization: enabled skia_renderer: enabled_on video_decode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	31.95GB (17.74GB free)
Process Argv	--crash-reporter-id e5e654ef-9a6a-490b-ab1a-fca91fec1429
Screen Reader	no
VM	0%

Extensions (22)

Extension	Author (truncated)	Version
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gitlens	eam	11.4.1
ev3dev-browser	ev3	1.2.0
matlab	Gim	2.0.1
beautify	Hoo	1.5.0
vscode-cudacpp	kri	0.1.1
ev3-micropython	leg	2.0.0
Kotlin	mat	1.7.1
dotenv	mik	1.0.1
vscode-clang	mit	0.2.3
vscode-docker	ms-	1.12.1
python	ms-	2021.4.765268190
jupyter	ms-	2021.5.745244803
remote-wsl	ms-	0.54.6
cmake-tools	ms-	1.7.1
cpptools	ms-	1.3.1
hexeditor	ms-	1.5.0
ejs-language-support	Qas	0.0.1
sass-indented	rob	1.5.1
shader	sle	1.1.5
cmake	twx	0.0.17
clang-format	xav	1.9.0

A/B Experiments

vsliv368cf:30146710
vsreu685:30147344
python383:30185418
vspor879:30202332
vspor708:30202333
vspor363:30204092
vstry914:30276682
pythonvsnew554cf:30291488
pythontb:30283811
pythonvspyt551cf:30291415
vspre833cf:30267465
pythonptprofiler:30281270
vshan820:30294714
pythondataviewer:30285071
vscus158cf:30286554
vscgsv2:30294352

[Tyriar]

alt+x,y,z works fine, just not for alt+0,0,0. Closing as designed since this alt sequence is something provided by the OS and it seems to work fine. Note that coming in the next version we'll have ctrl+shift+2 as a builtin keybinding for NUL which you could use instead: #135313