Autocomplete doesn't work if typescript in devDependencies in monorepos root package.json

[zerkalica]

Demo project: https://github.com/zerkalica/ts-references-autoimport-bug/tree/broken-autoimport-b

TypeScript Version: 4.0.2
VSCode Version: 1.49.2
OS: Ubuntu 20.04.1 LTS

Steps to reproduce

1. Clone, switch to broken-autoimport-b branch, yarn install
2. Open lib/b/b.ts in vscode, type someC
3. Expected: autoimport suggest import {someC} from '@some/lib-c', actual: no someC in autoimport

Autocomplete works if typescript present in dependencies section of root package.json:

1. Replace devDependencies to dependencies in root package.json
2. Restart tsserver or vscode
3. Open lib/b/b.ts in vscode, type someC
4. Expected and actual behavior: someC in autocomplete

TypeScript Version: 4.0.2

[andrewbranch]

No longer repros on TypeScript 4.1+