Language selector on CMS pages is showing too many languages

[stevejalim]

As we'll see when #14801 lands, there's currently a niggle where a page that intended for just one locale has all the other CMS-supported langages available in the language picker in the footer.

This may be a bug in the integration of the lang picker or it may just be that Wagtail is creating aliases of a the en-US page in all the other available locales and we don't want that.

Need investigation and is a blocker for turning on the CMS-backed leadership page in prod, so P2

[stevejalim]

cc @alexgibson for awareness

[janbrasna]

it's drawn from translations context that's being defined here on the render() for CMS pages:

bedrock/lib/l10n_utils/__init__.py

Lines 160 to 161 in 3e8f11b

	if is_cms_page and request._locales_available_via_cms:
	translations = request._locales_available_via_cms

so it's patched as:

bedrock/bedrock/cms/models/base.py

Lines 46 to 49 in 3e8f11b

	def _patch_request_for_bedrock(self, request):
	# Add hints that help us integrate CMS pages with core Bedrock logic
	request.is_cms_page = True
	request._locales_available_via_cms = [self.locale.language_code] + [x.locale.language_code for x in self.get_translations()]

to get the translations from get_translations() — they must be coming wrong from it already.

[stevejalim]

yeah, poking around lightly i can see that my local build has other locale versions of the test page i intended to be in en-US only, but saved as draft. So, two things there:

1. I didn't expect (or want) wagtail-loalize to auto-create versions of my test page in other locales - i would expect that only to happen if i hit 'translate this page', so that needs exploring - one that I will raise in the Wagtail Slack if I can't find docs about it

2. Looks like get_translations doesn't take into consideration whether a page is live or not:

https://github.com/wagtail/wagtail/blob/4af8ab528bc4439a3deb50b30d61324eb18871ed/wagtail/models/i18n.py#L287-L298

so we might be able to change things like this to skip the drafts, which is an important fix anyway, plus limit it to public (rather than password-protected) pages, too:

-      ... [x.locale.language_code for x in self.get_translations()] 
+      ... [x.locale.language_code for x in self.get_translations().live().public()]

[stevejalim]

Ah, I've got it - the other pages are live and public, but they're also auto-generated aliases of the page in question.

So I think we need to

1. def disable that auto-creation of aliases
2. to be extra sure, exclude aliased pages from the query used to get the relevant languages

[stevejalim]

@alexgibson I'd hold off merging (or at least trying to set up) #14801 till this is done in case we need to replumb anything

[stevejalim]

Moving the issues with auto-creation of alias pages to a separate ticket: #15063