Bug: Functions are exported as type-only from commonjs export of `@eslint/config-helpers`

[youngspe]

Which packages are affected?

• @eslint/compat
• @eslint/config-array
• @eslint/config-helpers
• @eslint/core
• @eslint/mcp
• @eslint/migrate-config
• @eslint/object-schema
• @eslint/plugin-kit

Environment

Node version: v23.10.0
npm version: 10.9.2
ESLint version: 10.2.0
Operating System: Ubuntu 24.04.4 LTS (through WSL)

What did you do?

My code was importing and calling defineConfig from 'eslint/config':

// eslint.config.mjs

import { defineConfig } from 'eslint/config';

defineConfig(/* ... */);

What did you expect to happen?

Ideally, this would type check without any errors.

What actually happened?

@typescript/native-preview gives the following error:

eslint.config.cjs:3:1 - error TS1361: 'defineConfig' cannot be used as a value because it was imported using 'import type'.                    
                                                                                                                                               
3 defineConfig(/* ... */);                                                                                                                              
  ~~~~~~~~~~~~                                                                                                                                 
                                                                                                                                               
  node_modules/@eslint/config-helpers/dist/cjs/index.d.cts:1:18 - 'defineConfig' was imported here.                                            
    1 import type * as types from "../esm/index.js" with { "resolution-mode": "import" };        

Link to Minimal Reproducible Example

https://github.com/youngspe/eslint-types-example

Participation

• I am willing to submit a pull request for this issue.

AI acknowledgment

• I did not use AI to generate this issue report.
• (If the above is not checked) I have reviewed the AI-generated content before submitting.

Additional comments

Looks like this was introduced by #416

@eslint/config-helpers/dist/cjs/index.d.cjs looks like this as of @eslint/config-helpers@0.5.2:

import type * as types from "../esm/index.js" with { "resolution-mode": "import" };
export = types;

Since the functions defineConfig and globalIgnores are imported through import types before being re-exported, they're techincally type-only exports.

This causes build errors with @typescript/native-preview@^7.0.0-dev.20260404.1 when calling those functions, either directly through '@eslint/config-helpers' from a commonjs module or through 'eslint/config' from any module. Curiously, typescript@6.0.2 is not reporting errors, though as far as I can tell it should because it's still a re-export of a type-only import.

This likely applies to other packages changed by #416 but I haven't checked that.

Feel free to close if this is a won't-fix because it only fails on a pre-production TypeScript compiler version.

[lumirlumir]

Hi @youngspe — thanks for the report. I can reproduce this with the TypeScript v7 native preview (@typescript/native-preview@^7.0.0-dev.20260404.1), and I've confirmed the error does not occur with TypeScript v6 (typescript@6.0.2).

I believe this issue is caused by TypeScript v7 enforcing stricter type tracking for re-exports than v6.

I'd be in favor of fixing this if a straightforward solution exists, since TypeScript v7 usage will likely increase over time. One concern, though, is that TypeScript v7 is still in development and, as mentioned, its behavior could change in the future.

What should our policy be regarding TypeScript v7 compatibility? Any thoughts, @eslint/eslint-team?

[DMartens]

I think we should start checking for TypeScript v7 support as soon as the first release candidate releases, which according to their blog post is only a few months away.

[youngspe]

My intuition is that we can just remove the type modifier from the import type statements in the generated d.cts files. Since they just re-export the ES module declaration, anything that's safe to import by value with import should be safe to import with require(). But there could definitely be something I'm missing.

[eslint-github-bot]

👋 Hi! This issue is being addressed in pull request #426. Thanks, @youngspe!