Two full TS servers spawned for on TS 3.9.x

[mjbvz]

Issue Type: Bug

repo

1. npm i -g [email protected]

2. Set your user tsdk to use this version, for example:

   	"typescript.tsdk": "/Users/matb/.nvm/versions/node/v12.14.0/lib/node_modules/typescript/lib"
   

3. Now load the VS Code workspace (making sure you are using your user TS version)

4. Open a file in src and try getting the document outline

Bug
Big delay.

This is because two full TS Servers are being spawned instead of a syntax only server + full server (see memory usage in screenshot):

VS Code version: Code - Insiders 1.48.0-insider (4c23fc2, 2020-08-11T10:13:04.551Z)
OS version: Darwin x64 19.6.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz (16 x 2400)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_renderer: disabled_off_ok video_decode: enabled viz_display_compositor: enabled_on viz_hit_test_surface_layer: disabled_off_ok webgl: enabled webgl2: enabled
Load (avg)	6, 6, 5
Memory (System)	32.00GB (3.02GB free)
Process Argv	-psn_0_42174518
Screen Reader	no
VM	14%

[mjbvz]

Seems like this was caused by #104123

[mjbvz]

For verification, try the following cases:

• Using TS 3.9.7
• Using TS 4.0.1-rc
• Using TS@next
• Using an old TS version like 3.5 (older versions don't support the syntax server at all)

All should load the document symbols quickly even while the loading spinner is showing

You can use the same global install in all cases, just make sure to reload VS Code each time

[isidorn]

Assigning this to july milestone since it is a candidate.

[isidorn]

@mjbvz following your steps I have verified that the outline get loaded quickly, however I still see two tsservers spinning up when I open the process explorer. If I understood correctly this is by design, since only one of them has a large memory usage.
I have verified for TS: 3.9.7, 4.0.1-rc. ts@next, 3.5
Thus adding verified label