rustauth-i18n

Internationalization plugin for RustAuth.

What It Is

rustauth-i18n localizes RustAuth JSON error responses. It detects a locale, looks up the response code in your dictionaries, replaces message, and preserves the original message as originalMessage.

What It Provides

Translation dictionaries keyed by RustAuth error code.
Locale detection from Accept-Language, cookies, session fields, or sync/async resolver callbacks.
Fallback locale handling.
A server-side plugin that can be registered with RustAuth::builder().

Quick Start

use rustauth::i18n::{i18n, I18nOptions, LocaleDetectionStrategy};
use rustauth::RustAuth;

let auth = RustAuth::builder()
    .secret("secret-a-at-least-32-chars-long!!")
    .plugin(i18n(
        I18nOptions::new()
            .locale("en", [("INVALID_EMAIL", "Invalid email")])
            .locale("es", [("INVALID_EMAIL", "Email invalido")])
            .default_locale("en")
            .detection([
                LocaleDetectionStrategy::Cookie,
                LocaleDetectionStrategy::Header,
            ]),
    )?)
    .build()?;
# let _ = auth;
# Ok::<(), Box<dyn std::error::Error>>(())

Notes

For migrations from an existing IndexMap of locale tables, use I18nOptions::from_translations(map) instead of building dictionaries by hand.
Accept-Language tries exact tags before base tags, for example pt-BR before pt.
Cookie detection defaults to the locale cookie.
Session detection defaults to a user/session locale field.
Async locale callbacks use get_locale_async and require AuthRouter::handle_async (or the RustAuth async server path). Sync AuthRouter::handle keeps synchronous get_locale only.

Status

Experimental beta. Locale detection, translation keys, and plugin behavior may change before stable release.

Better Auth compatibility

Server-side i18n plugin that localizes JSON error responses by error code. Aligned with Better Auth 1.6.9 where it matters; RustAuth is not a line-by-line port.

For route-level parity, test counts, intentional differences, and known gaps, see UPSTREAM.md.

rustauth-i18n 0.3.2