vscode: VSCODE_PID not set on Linux, preventing debug-auto-attach from working

Issue Type: Bug

I was investigating the Auto Attach feature not working on my Ubuntu box. I noticed that VSCODE_PID was used:

https://github.com/Microsoft/vscode/blob/bc24f98b5f70467bc689abf41cc5550ca637088e/extensions/debug-auto-launch/src/extension.ts#L120-L128

If I understand correctly, the extension.node-debug.startAutoAttach is created there:

https://github.com/Microsoft/vscode-node-debug/blob/dd8fca03672e05eca5d1e8e36f99c3a7f835459d/src/node/extension/autoAttach.ts#L57-L67

Thing is I don’t think VSCODE_PID is set on Linux (not set in integrated terminal shells; in dev tools process.env.VSCODE_PID doesn’t exist). The rootPid given is set by default to 0.

Sorry for not having investigating further. 🙄 I’ll try to clone vscode and debug from there.

cc @weinand

VS Code version: Code 1.29.1 (bc24f98b5f70467bc689abf41cc5550ca637088e, 2018-11-15T19:07:43.495Z) OS version: Linux x64 4.15.0-39-generic

System Info

Item	Value
CPUs	Intel® Core™ i7-4770 CPU @ 3.40GHz (4 x 3392)
GPU Status	2d_canvas: enabled checker_imaging: disabled_off flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software rasterization: disabled_software video_decode: unavailable_software video_encode: unavailable_software webgl: enabled webgl2: enabled
Load (avg)	1, 1, 1
Memory (System)	7.77GB (0.89GB free)
Process Argv	–proxy-server=localhost:3128 .
Screen Reader	no
VM	100%

Extensions (27)

Extension	Author (truncated)	Version
project-manager	ale	9.1.0
insertnumbers	Asu	0.9.1
vscode-gpm	axe	1.0.0
solargraph	cas	0.17.6
npm-intellisense	chr	1.3.0
vscode-markdownlint	Dav	0.21.0
xml	Dot	2.3.2
EditorConfig	Edi	0.12.5
tslint	eg2	1.0.40
vscode-npm-script	eg2	0.3.5
prettier-vscode	esb	1.7.2
shell-format	fox	1.1.3
randomeverything	hel	0.0.3
Go	ms-	0.7.0
vscode-jest	Ort	2.9.2
vscode-docker	Pet	0.4.0
ruby	reb	0.20.0
java	red	0.34.0
rewrap	stk	1.9.1
shellcheck	tim	0.6.0
vscode-input-sequence	tom	0.2.0
vscode-java-debug	vsc	0.15.0
vscode-java-pack	vsc	0.4.0
vscode-java-test	vsc	0.10.0
vscode-maven	vsc	0.11.1
change-case	wma	1.0.0
markdown-all-in-one	yzh	1.7.0