Latest post block: show child categories when parent category is selected

[annezazu]

When using the Latest Posts Block with a Category filter, the post assigned only to Child Categories should also be listed, respecting the hierarchy. Right now, filtering by a Parent Category will only display posts namely assigned to the Parent Category. To list both Parent and Child Category posts, the both categories need to be present in the filter, as seen below in the following video:

parent.and.child.mov

If this is done for a reason, curious to hear why and we can close this out too! It just seems odd that the Category Page for a Parent Category lists posts from Child Categories but the Latest Posts Block doesn't.

[justintadlock]

It looks like this block uses category__in to grab only posts directly in the chosen category: https://github.com/WordPress/gutenberg/blob/trunk/packages/block-library/src/latest-posts/index.php#L55-L57

category__in specifically ignores child categories: https://developer.wordpress.org/reference/classes/wp_query/#category-parameters

The Query Loop block would use tax_query instead. There are other options for this block, though. Probably the easiest change is to use cat.

Edit: It looks like category__in was originally added here: #20781 (comment)