CLI to find unused/missing translations

[simonlovesyou]

Hey!

At my previous engagement we developed a CLI to find unused or missing translations with static code analysis. It was closed source unfortunately, but would there be any interest in integrating it to next-intl if I were to rebuild it, but open source? :) If so, any thoughts on what the features set should be? There are also some different choices we can make in terms of user configuration, preferred libraries to use etc.

This is relevant to Linting unused strings · amannn/next-intl · Discussion #398

EDIT: On second thought it could even be integrated as an eslint rule instead of a separate CLI if we would prefer that.

[amannn]

Hey @simonlovesyou, thank you so much for starting this discussion! There's no CLI or ESLint plugin planned at this point, but I'm absolutely open to discussing this!

Would you like to implement and provide this under your own GitHub user or in this repo? Both is totally fine IMO, we can link to it from the workflows & integrations page in the docs.

I like your idea about having an ESLint plugin, mostly because many developers already use ESLint and therefore it's easy to integrate with their toolchain. In regard to other rules, a no-deprecated rule could be interesting to help users migrate when APIs need to be changed—this is something I already considered. In regard to messages handling I could also imagine a sort-keys rule that is autofixable and makes sure that messages files are consistently structured. I personally use the i18n Ally VSCode extension that does the sorting, not sure if it's worth implementing this ourselves.

But starting with an ESLint plugin with a single rule could still be useful IMO.

Do you have experience with building something like this? I'm wondering how this would impact editor performance or, more generally, ESLint runtime performance. When are messages files checked? Are there parts of the linting process that can be cached?

A CLI might be less performance-sensitive since a user would explicitly call the CLI e.g. on CI (see also #398 (comment)).

What's your opinion?

/cc @kieranm

[kieranm]

I tried to write an ESlint rule for this and failed miserably. ESLint seems to analyse files independently and so there doesn't appear to be a way of determining whether something is used or unused globally across the whole codebase. I could be missing something big though as my ESLint knowledge is very limited

[amannn]

I just noticed i18n Ally has a usage report, this could be helpful in this context:

It currently reports a few false positives for me though, due to pending support for getTranslations (useTranslations seems to work fine).