make return type of t a branded type like TranslatedString rather than plain string to aid type safety

[WickyNilliams]

🚀 Feature Proposal

It would be useful if the t function returned a branded type, rather than a plain string, so that you can enforce at a type level that a function/component/other is receiving a translated string.

Motivation

Consider you have a function showToast which can be called from anywhere in the app to show a message to the user e.g.

function showToast(message: string) {
  // ...
}

in the ideal, all strings passed to it have been translated:

showToast(t("some.key"))

but there is nothing stopping you from doing:

showToast("oops not translated") // no type error :(

this will produce no errors, and can only be caught through ongoing diligence and manual review. as such, this is error prone.

It would be useful if the t function returned a branded type like

type TranslatedString = string & { __type: "TranslatedString" }

Example

with a branded type you can enforce via the type system that untranslated strings are not propagating through the system:

function showToast(message: TranslatedString) {
  // ...
}

showToast("oops not translated") // type error 🎉 

[adrai]

isn't this already done by @jtbandes ? #1994

[WickyNilliams]

I looked at that before posting, i think it's a different thing? that seems to be related to accepting the t function itself as a param, whereas i'm talking about accepting the return type of t function as a param. correct me if i'm wrong! i'd be happy if this is already available :)

[jtbandes]

This is a good idea, but might be an even bigger breaking change than mine was 😅

[WickyNilliams]

haha yes, very possible it would be. wondering if it could be opt-in behavior, via config or via a new t function, so that it doesn't blow up a million codebases. for existing projects this would need to be carefully managed. but for greenfield, i expect many would want this (i am in this position :))

[jtbandes]

Yes, I’m sure you could make it opt-in via CustomTypeOptions or something like that.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[WickyNilliams]

Don't close please :)