Monorepo shared tools package TypeScript config file

Describe the bug

I found a bug in my monorepo where the extension failed discover tests when a vitest.config.ts imports a shared config helper through a workspace package export like:

import { createStandardVitestConfig } from '@org/common-tools-package/vitest/setup';

It turns out the extension was throwing an error:

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for .../packages/common-tools-package/src/vitest/setup.ts

In a terminal I can run vitest and it resolves and loads the shared package's import to the setup.ts file.

Expected behavior

Extension shows tests (w/o logged errors) for a monorepo package that imports a shared config from a common package.

Reproduction

Example Repo:

repo-root/
├─ package.json
└─ packages/
   ├─ package-a/
   │  ├─ package.json
   │  ├─ vitest.config.ts
   │  └─ src/
   │     └─ example.test.ts
   └─ common-tools-package/
      ├─ package.json
      └─ src/
         └─ vitest/
            ├─ setup.ts
            └─ vitest-config.ts

packages/common-tools-package/package.json:

{
  "name": "@org/common-tools-package",
  "type": "module",
  "exports": {
    "./vitest/setup": {
      "types": "./src/vitest/setup.ts",
      "import": "./src/vitest/setup.ts",
      "require": "./src/vitest/setup.ts",
      "default": "./src/vitest/setup.ts"
    }
  }
}

Note that if I don't use the @org/common-tools prefix and use a direct-on-disk path import like: import { createStandardVitestConfig } from '../common-tools-package/src/vitest/setup.ts' the extension can load that shared setup.ts and I can execute tests in my IDE.

Output

[INFO 2:23:41 PM] [API] Running Vitest v4.1.2 (example/vite.config.ts) with "/home/soconnor/.nvm/versions/node/v22.14.0/bin/node /home/soconnor/.vscode/extensions/vitest.explorer-1.50.4/dist/worker.js"
[2:23:41 PM] [VSCODE] Flushing 1 changed items
[Error 2:23:41 PM] There were errors during config load.
[Error 2:23:41 PM] [Error Error] Vitest failed to start: 
TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /home/soconnor/dev/package-a/client/packages/tools/src/vitest/setup.ts
    at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:219:9)
    at defaultGetFormat (node:internal/modules/esm/get_format:245:36)
    at defaultLoad (node:internal/modules/esm/load:120:22)
    at async ModuleLoader.loadAndTranslate (node:internal/modules/esm/loader:514:32)
Error: Vitest failed to start: 
TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /home/soconnor/dev/package-a/client/packages/tools/src/vitest/setup.ts
    at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:219:9)
    at defaultGetFormat (node:internal/modules/esm/get_format:245:36)
    at defaultLoad (node:internal/modules/esm/load:120:22)
    at async ModuleLoader.loadAndTranslate (node:internal/modules/esm/loader:514:32)
	at e.u (/home/soconnor/.vscode/extensions/vitest.explorer-1.50.4/dist/extension.js:1:59239)
	at e.emit (node:events:519:28)
	at e.o.t.exports.ae (/home/soconnor/.vscode/extensions/vitest.explorer-1.50.4/dist/wrapper-Br94zcvg.js:1:38577)
	at e.o.t.exports.emit (node:events:519:28)
	at e.o.t.exports.dataMessage (/home/soconnor/.vscode/extensions/vitest.explorer-1.50.4/dist/wrapper-Br94zcvg.js:1:16501)
	at e.o.t.exports.getData (/home/soconnor/.vscode/extensions/vitest.explorer-1.50.4/dist/wrapper-Br94zcvg.js:1:15398)
	at e.o.t.exports.startLoop (/home/soconnor/.vscode/extensions/vitest.explorer-1.50.4/dist/wrapper-Br94zcvg.js:1:12110)
	at e.o.t.exports._write (/home/soconnor/.vscode/extensions/vitest.explorer-1.50.4/dist/wrapper-Br94zcvg.js:1:11402)
	at writeOrBuffer (node:internal/streams/writable:572:12)
	at _write (node:internal/streams/writable:501:10)
	at Writable.write (node:internal/streams/writable:510:10)
	at Socket.Z (/home/soconnor/.vscode/extensions/vitest.explorer-1.50.4/dist/wrapper-Br94zcvg.js:1:39601)
	at Socket.emit (node:events:519:28)
	at addChunk (node:internal/streams/readable:561:12)
	at readableAddChunkPushByteMode (node:internal/streams/readable:512:3)
	at Readable.push (node:internal/streams/readable:392:5)
	at TCP.onStreamRead (node:internal/stream_base_commons:189:23)
	at TCP.callbackTrampoline (node:internal/async_hooks:130:17)

Extension Version

1.50.4

Vitest Version

4.1.2

Validations

• Check that you are using the latest version of the extension
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

Start by reproducing the failure with packages/package-a/vitest.config.ts importing packages/common-tools-package/src/vitest/setup.ts through the package.json exports. Compare the extension's behavior with terminal Vitest and inspect the config-loading path around the worker.js entry point. Done means the extension discovers the tests without logged config-load errors.