Repository: TypeScript
Issue: Intellisense fails for TS on "completionInfo"
Labels: Bug,Rescheduled

Type: <b>Bug</b>

Intellisense fails a few seconds after TS server runs. It seems related to the `completionInfo` request to TS server.

If we restart TS server and try get Intellisense suggestions right away, it works:

![image](https://github.com/microsoft/vscode/assets/2132564/d123e740-14a7-47d3-b538-3326d4a2edc0)

But after a few seconds (~5s), it stops working:

![image](https://github.com/microsoft/vscode/assets/2132564/54645c95-633a-420a-95a6-6ef67f3a460e)

Steps to Reproduce:

1. Clone https://github.com/metriport/metriport
2. Checkout branch `944-tmp-no-fhir-converter`
3. Open `packages/api/src/app.ts`
4. `npm run install-deps && npm run build`
5. Somewhere below line 15, type `ver` and wait for Intellisense to kick-in
6. If done right after TS server starts, it should work (shows suggestion with icon "box within brackets")
7. If done ~5s after TS server starts, it should fail (shows suggestion with icon `abc`)

Looking at the TS server log, we get this:

```
Err 751   [18:43:42.056] Exception on executing command {
  "seq": 34,
  "type": "request",
  "command": "completionInfo",
  "arguments": {
    "file": "/Users/rafael/code/metriport/packages/api/src/app.ts",
    "line": 18,
    "offset": 2,
    "includeExternalModuleExports": true,
    "includeInsertTextCompletions": true,
    "triggerKind": 1
  }
}:

    Cannot read properties of undefined (reading 'lastIndexOf')

    TypeError: Cannot read properties of undefined (reading 'lastIndexOf')
        at Object.startsWith (/Users/rafael/code/metriport/node_modules/typescript/lib/tsserver.js:2290:20)
        at getNodeModuleRootSpecifier (/Users/rafael/code/metriport/node_modules/typescript/lib/tsserver.js:132350:20)
        ...
```

Full TS server log: [tsserver.log](https://github.com/microsoft/vscode/files/12307596/tsserver.log)

This fails on MacOS `13.4.1`, but we couldn't reproduce it on Windows 10 (it works even after a few seconds of restarting the TS server).

Additional env info:
- npm: `9.5.1`
- node: `v18.14.2`
- VSCode: `1.81.0` (also tried on `1.79` and "Insiders")
- TS version 4.9.5

VS Code version: Code 1.81.0 (Universal) (6445d93c81ebe42c4cbd7a60712e0b17d9463e97, 2023-08-02T12:40:02.782Z)
OS version: Darwin arm64 22.5.0
Modes:

<details>
<summary>System Info</summary>

|Item|Value|
|---|---|
|CPUs|Apple M1 Max (10 x 24)|
|GPU Status|2d_canvas: enabled<br>canvas_oop_rasterization: disabled_off<br>direct_rendering_display_compositor: disabled_off_ok<br>gpu_compositing: enabled<br>metal: disabled_off<br>multiple_raster_threads: enabled_on<br>opengl: enabled_on<br>rasterization: enabled<br>raw_draw: disabled_off_ok<br>video_decode: enabled<br>video_encode: enabled<br>vulkan: disabled_off<br>webgl: enabled<br>webgl2: enabled<br>webgpu: enabled|
|Load (avg)|24, 19, 15|
|Memory (System)|32.00GB (0.08GB free)|
|Process Argv|--disable-extensions --crash-reporter-id c22e1216-d117-446f-9db4-d73fbdb3e601|
|Screen Reader|no|
|VM|0%|
</details>Extensions disabled<details>
<summary>A/B Experiments</summary>

```
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vsreu685:30147344
python383:30185418
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pythonvs932:30410667
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c4g48928:30535728
dsvsc012:30540252
pynewext54:30695312
azure-dev_surveyone:30548225
vscccc:30803845
282f8724:30602487
89544117:30613380
a9j8j154:30646983
showlangstatbar:30737416
vsctsb:30748421
a2ce3375:30757347
pythonfmttext:30731395
pythoncmvfstrcf:30756944
9b8hh234:30694863
fixshowwlkth:30771522
showindicator:30805244
pythongtdpath:30769146
i26e3531:30792625
gsofa:30804715
pythonnosmt12:30797651
pythonidxptcf:30805731
pythonnoceb:30805159
e537b577:30795824
dsvsc013:30795093
dsvsc014:30804076

```

</details>

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