Imported TypeScript files in ``eslint.config.ts`` doesn't work

[ferferga]

The following structure is publicily available at https://github.com/jellyfin/jellyfin-vue

Steps to reproduce

1. Click on Code > Create codespace from master (or clone the repository locally)
2. cd frontend && npm run lint:inspect

Description

This an overview of the setup

• Using TypeScript configuration files with jiti v2. Looks like that is already covered
• A monorepo (called @jellyfin-vue/configs in my case) where TypeScript modules export factory functions for rule configs.
• Those factory functions are imported in frontend/eslint.config.ts, working perfectly with ESLint but not with the inspector.

[voxpelli]

I have a hard time understanding what it is that doesn’t work.

Can you maybe add a screenshot or something where you show what’s wrong or missing?

[ferferga]

@voxpelli I was able to better triage the issue and create a minimal reproduction: https://stackblitz.com/edit/vitejs-vite-9abzaz

Steps to reproduce

1. cd packages/configs and run npm run lint:inspect
2. ESLint config inspector will load successfully, since the TypeScript file imported is referenced from the same project
3. Change to the packages/main directory and run npm run lint:inspect there. The config inspector will fail to load with the following error, since the base rules are being imported from the monorepo:
   

Additional context

It looks like the issue exists when importing .ts files from node_modules in monorepo setups. Similar to what happens in Vite. Hence, the workarounds listed there are also applicable to this project

[KryziK]

I'm running into this same issue. I have two projects:

• An ESLint Shared Config project which directly exports .ts files instead of transpiling
• A consuming project whose eslint.config.ts simply re-exports the config from the above project

Running eslint (with any of --fix, --debug, --print-config) works just fine, but specifically only the inspector fails with:

ℹ Reading ESLint config from C:\project2\eslint.config.ts
Failed to load `eslint.config.js`.
Note that `@eslint/config-inspector` only works with the flat config format:
https://eslint.org/docs/latest/use/configure/configuration-files-new
TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for C:\project2\node_modules\project1\src\index.ts
    at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:218:9)
    at defaultGetFormat (node:internal/modules/esm/get_format:244:36)
    at defaultLoad (node:internal/modules/esm/load:122:22)
    at async ModuleLoader.loadAndTranslate (node:internal/modules/esm/loader:483:32) {

I am not well-versed enough in js/ts/frontend to understand what I can do to work around this issue.

[antfu]

I don't think it's a good practice to ship .ts directly to npm, at least not until Node v23+, which ships the strip-types feature by default. I consider this as an expected behaviour as this is out-of-scope for jiti to handle files inside node_modules

[KryziK]

In my case, these are private, scoped packages that my team uses internally via Azure Artifacts.