Type-safe message authoring

[musjj]

I want to have completions and type-checking while authoring my messages, so that I won't forget to include certain namespaces, etc. The docs suggests something like this:

global.d.ts

import en from './messages/en.json';
 
type Messages = typeof en;
 
declare global {
  // Use type safe message keys with `next-intl`
  interface IntlMessages extends Messages {}
}

This is useful for type-inferring the messages you've written for a single locale, but it doesn't help ensure that your messages are uniform and correct across all locales.

I'm thinking of just using .ts files for my messages so that I can just directly typecheck them, like this:

./messages/en.ts

import type { Messages } from "./schema.ts";

export default {
  ...
} satisfies Messages;

But is this a good practice? Is there a downside to this approach? I considered using JSON schemas, but I feel that would complicate the build process and code generation.

[amannn]

A downside of this approach is that unlike JSON files, messages in source code might not be compatible with other tools like the VSCode integration for next-intl or translation management systems like Crowdin. Such translation management systems are also really good at helping you ensure that messages are in sync across all locales—maybe something you could consider!