Add hreflang to the HTML head on all pages

This issue is being reviewed by the kind folks in Slack, #needs-review-queue-initiative. We are working to keep the size of Needs Review queue [2700+ issues] to around 400 (1 month or less), following Review a patch or merge request → as a guide.

Tagging for issue summary update with what the proposed solution should be.
As noted in #18

It's not clear to me why the hreflang link tags should only be generated for translated entities. Other pages, such as views, and untranslated content with a translated user interface, need them too.

So what is the desired behavior here?

Also meant to tag for accessibility if they can offer guidance

I'm not sure as I didn't file this issue, but I think it's a feature request for core to generate hreflang tags on pages that are not translated entities. Or it could also be thought of as a bug report on the existing feature, where core generates hreflang tags only for translated entity pages.

On a typical multilingual site, other kinds of pages (e.g. the default front page, /node, which is a view page) can be accessed in different languages - which would show some mix of translated user interface and/or translated content - and for SEO purposes you'd want to have hreflang tags on these pages.

At the moment this feature is provided by contrib Hreflang module → , which has ~12,500 installs on drupal 7 thru 10, so seems potentially useful enough to be part of core, but *shrug* could also be won't fixed if core is not interested.

Seems like it wouldn’t be terrible to fold that in but don’t know the process for that

Adding 🐛 Hreflang on non-canonical content pages Needs work as a related issue as it has to do with hreflang. (Tl;dr: There's an assumption that hreflang and other meta tags can be built up in the #attached array where they will be automatically de-duplicated and other modules can alter them. But in fact, the hreflang tags should change depending on the query arguments on the page, and so I think they should be using a placeholder that gets swapped out at the last minute via a lazy builder. Although this change would be a BC break.)

But in fact, the hreflang tags should change depending on the query arguments on the page, and so I think they should be using a placeholder that gets swapped out at the last minute via a lazy builder. Although this change would be a BC break.)

If it's just changing something in a render array, that's fine with a change record / release notes mention in a minor release.

I can't see a patch here, so switching the status to 'active', this seems reasonable to add but I don't think it's a bug as such (and the contrib module can be used in the meantime), so moving to 'task'.