Respond to Rollup warning for i18n.mjs

What

This notice, which we think is coming from Rollup, currently appears in the test output:

Entry module “src/govuk/i18n.mjs” is implicitly using “default” export mode, which means for CommonJS output that its default export is assigned to “module.exports”. For many tools, such CommonJS output will not be interchangeable with the original ES module. If this is intended, explicitly set “output.exports” to either “auto” or “default”, otherwise you might want to consider changing the signature of “src/govuk/i18n.mjs” to use named exports only.

Understand whether there are implications for consumers of GOV.UK Frontend and whether we need to make any changes.

If we don’t need to make any changes, see if there’s a way to silence the warning.

Why

src/govuk/i18n.mjs is a new file which has not yet been included in a release of GOV.UK Frontend.

We want to make sure that the way that we’ve written i18n.mjs will not impact consumers of GOV.UK Frontend once the next release has gone out.

Who needs to work on this

Developers

Who needs to review this

Developers

Done when

• We understand the implications of the warning
• We’ve made any changes required before shipping the next release
• The warning no longer appears in the test output (unless it’s not possible to silence it)

[romaricpascal]

Maybe using a named export would make the warning disappear, as it seems to complain about the export being a default one. If that’s the case, that might be a cheap, quick fix for the warning 😄

[querkmachine]

Maybe this is something to discuss as a team? At the very least I’d like to check in with @querkmachine and see how it would feel about making it public now.

I don’t think there’s anything stopping I18n from being public.

It’s been built around the needs of our existing components and is definitely not the most fully-featured i18n script around (no genders, contextual grammar, etc.), so external users may run into the limitations of it harder than we have, but it does work (🤞).