disallow-stylelint-duplicate-extends

Disallow duplicate entries in top-level Stylelint extends declarations.

Targeted pattern scope

This rule targets Stylelint config modules such as stylelint.config.ts, stylelint.config.mjs, and .stylelintrc.js.

It focuses on top-level exported config objects, including configs wrapped in defineConfig(...).

What this rule reports

Reports duplicate string entries in top-level extends arrays.

Why this rule exists

Duplicate shared-config layers add noise and can obscure real config intent.

❌ Incorrect

export default {
    extends: ["stylelint-config-standard", "stylelint-config-standard"],
    rules: {},
};

✅ Correct

export default {
    extends: ["stylelint-config-standard"],
    rules: {},
};

Behavior and migration notes

This rule auto-fixes by keeping the first occurrence of each entry.

ESLint flat config example

import stylelint2 from "eslint-plugin-stylelint-2";

export default [stylelint2.configs.configuration];

When not to use it

Do not use this rule if your repository intentionally keeps duplicate entries for generated tooling compatibility.

Package documentation

Stylelint package documentation:

Rule catalog ID: R023

Further reading

• Stylelint extends