The translation being passed to determine if translation access is the source translation, not the target. But we should be identifying if the entity is translatable from the target. There is even a contrib module → that takes advantage of this feature by creating more fine grained permissions based on per language access. This should be adjusted so we use the target language.
Install allowed_languages v2. Add a couple or more languages to the site. Add a user who has access to edit a page content type and (via allowed languages module) access for a single language. As an admin user, create a page in another source language. Then login as the user who has access to the single user. This single user has UI elements to translate into their single language. But the save button is missing.
Pass along the target language entity, not the source to the permission checking.
Needs work
10.1 ✨
The change is currently missing an automated test that fails when run with the original code, and succeeds when the bug has been fixed.
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
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.
This could use a test case to show the use case where this bug (if still one) pops up.
Thanks!