prefer-i18n-default-locale-first

Prefer placing i18n.defaultLocale first in i18n.locales.

Targeted pattern scope

This rule targets docusaurus.config.* files and inspects the i18n object when locale arrays are statically resolvable.

What this rule reports

This rule reports when i18n.locales includes defaultLocale but does not place it at index 0.

Why this rule exists

Putting defaultLocale first makes locale-priority intent immediately visible and keeps locale arrays easier to audit during reviews.

❌ Incorrect

export default {
    i18n: {
        defaultLocale: "en",
        locales: ["fr", "en"],
    },
};

✅ Correct

export default {
    i18n: {
        defaultLocale: "en",
        locales: ["en", "fr"],
    },
};

Behavior and migration notes

This rule autofixes inline locale arrays by moving the first defaultLocale occurrence to the front.

For identifier-backed locale arrays, it reports and provides a suggestion that replaces the property value with an explicit reordered array literal.

When not to use it

Do not use this rule if your team intentionally uses a different locale ordering convention.

Rule catalog ID: R055

Further reading

• Docusaurus i18n guide