Terminal does not show ANSI underline

[krlmlr]

Issue Type: Bug

Characters marked as ANSI underline don't show as underlined in the terminal. Reproduce with

echo -e "\033[4mabc\033[24m"

in a bash terminal.

This is relevant for code that uses the underline to highlight parts of the output, e.g. the pillar R package.

VS Code screenshot

Built-in terminal screenshot

Version info

VS Code version: Code 1.55.0 (c185983, 2021-03-30T16:02:21.560Z)
OS version: Linux x64 5.8.0-48-generic snap

System Info

Item	Value
CPUs	AMD Ryzen 7 PRO 4750U with Radeon Graphics (16 x 2655)
GPU Status	2d_canvas: unavailable_software gpu_compositing: disabled_software multiple_raster_threads: enabled_on oop_rasterization: disabled_off opengl: disabled_off protected_video_decode: disabled_off rasterization: disabled_software skia_renderer: enabled_on video_decode: disabled_software vulkan: disabled_off webgl: unavailable_software webgl2: unavailable_software
Load (avg)	1, 1, 1
Memory (System)	30.66GB (10.50GB free)
Process Argv	. --no-sandbox --crash-reporter-id db0e5a34-7e40-4a40-8b97-4d06966f70f1
Screen Reader	no
VM	0%
DESKTOP_SESSION	ubuntu
XDG_CURRENT_DESKTOP	Unity
XDG_SESSION_DESKTOP	ubuntu
XDG_SESSION_TYPE	x11

Extensions (74)

Extension	Author (truncated)	Version
terraform	4op	0.2.1
key-bindings-to-md	akh	0.4.0
Bookmarks	ale	13.0.4
swagger-viewer	Arj	3.0.1
code-gnu-global	aus	0.2.2
vscode-bazel	Baz	0.4.0
npm-intellisense	chr	1.3.1
path-intellisense	chr	2.3.0
gitignore	cod	0.6.0
bracket-pair-colorizer-2	Coe	0.2.0
vscode-test-explorer-status-bar	con	1.1.2
vscode-markdownlint	Dav	0.40.1
vscode-eslint	dba	2.1.19
githistory	don	0.6.16
xml	Dot	2.5.1
gitlens	eam	11.3.0
vscode-html-css	ecm	1.10.2
EditorConfig	Edi	0.16.4
graphviz-preview	EFa	1.3.3
vscode-npm-script	eg2	0.3.19
vscode-test-explorer-diagnostics	emi	0.1.1
prettier-vscode	esb	6.3.2
lex-flex-yacc-bison	fau	0.0.3
terminal	for	0.0.10
vscode-google-translate	fun	1.4.12
vscode-pull-request-github	Git	0.25.0
go	gol	0.24.0
todo-tree	Gru	0.0.209
vsc-essentials	Gyd	0.4.0
terraform	has	2.9.1
vscode-test-explorer	hbe	2.19.6
r	Iku	1.6.6-pre-2
r-pack	Iku	0.0.2
smarty	imp	0.3.0
latex-workshop	Jam	8.16.1
vscode-edit-csv	jan	0.5.6
vscode-todo-highlight	jgc	2.0.1
vscode-graphviz	joa	0.0.6
ldif	jta	0.2.0
language-julia	jul	1.1.38
bash-ide-vscode	mad	1.11.0
autoconf	mae	0.1.0
hledger-vscode	mar	0.0.7
CursorColumnSelectOnTrueLines	mar	0.0.2
vscode-r-test-adapter	mea	0.3.0
git-graph	mhu	1.30.0
vscode-docker	ms-	1.11.0
mssql	ms-	1.10.1
python	ms-	2021.3.680753044
vscode-pylance	ms-	2021.3.4
jupyter	ms-	2021.5.702919634
remote-ssh	ms-	0.65.1
remote-ssh-edit	ms-	0.65.1
cpptools	ms-	1.3.0-insiders3
vsliveshare	ms-	1.0.4070
color-highlight	nau	2.3.0
indent-rainbow	ode	7.5.0
material-icon-theme	PKi	4.6.0
polacode	pnp	0.3.4
r-debugger	RDe	0.4.6
java	red	0.76.0
vscode-yaml	red	0.17.0
r-lsp	REd	0.1.14
multi-command	ryu	1.5.0
flymaps	Shi	0.0.4
vscode-status-bar-format-toggle	tom	2.0.0
when-suggest	use	0.0.6
vscodeintellicode	Vis	1.2.12
vscode-java-debug	vsc	0.32.1
vscode-java-dependency	vsc	0.18.2
vscode-java-pack	vsc	0.13.0
vscode-java-test	vsc	0.28.1
vscode-maven	vsc	0.28.0
markdown-all-in-one	yzh	3.4.0

A/B Experiments

vsliv368cf:30146710
vsreu685:30147344
python383cf:30185419
vspor879:30202332
vspor708:30202333
vspor363:30204092
vstry244:30276681
pythonvsdeb440:30248342
pythonvsded773:30248341
pythonvspyt875:30259475
pythonvspyt639:30281910
pythontb:30283811
wslfolderdoccf:30282075
vspre833:30267464
pythonptprofiler:30281270
vsdfh931:30280409
vshan820:30276952
pythondataviewer:30285071

[Tyriar]

/duplicate #121023