Lingui usage example to translate a string on a Next.js API call

[MurzNN]

I need to return a translated string on a Next.js API call response, but I can't find the correct way to do this in the documentation, so could anybody please share an example of how to do this right?

Here is an example of the ideal solution - file src/app/api/test2/route.ts:

import { t } from "@lingui/core/macro";
import { setI18n } from "@lingui/react/server";

export function GET() {
  const locale = 'de' // Will be reworked to get from the URL like `?lang=de`.
  setI18n(locale);
  const output = t`Homepage`
  return new Response(output)
}

But it doesn't work. So, could anyone please share a working code for this using the recommended approach?

[MurzNN]

Here is my version that works - file src/app/api/test2/route.ts:

import { getI18nInstance } from "@/appRouterI18n";
import { msg } from "@lingui/core/macro";

export function GET() {
  const locale = 'de' // Will be reworked to get from the URL like `?lang=de`.
  const i18n = getI18nInstance(locale)
  const output = i18n._(msg`Homepage`)
  return new Response(output)
}

It works, but this part i18n._(msg - looks pretty ugly. So, maybe more prettier way exists to achieve the same?

[MurzNN]

If the approach with i18n._(msg`Homepage`) is still correct and the optimal way, maybe create another macro that simplifies this code?

[vonovak]

You can use

t(customI18n)`Attachment ${name} saved`;

See https://lingui.dev/ref/macro#examples-of-js-macros

[MurzNN]

Thanks, tried this now - it works, but produces a deprecation warning:

export function t(i18n: I18n): {
@deprecated
in v5, would be removed in v6. Please use i18n._(msg`Hello ${{name}}`) instead

So, seems no simple macro usage is possible, only a complex construction with two function calls?

[timofei-iatsenko]

Yes, this one is deprecated, recommended way is to use i18n._(msg`Homepage`)