Categories in Jekyll content that aren't files?

I’ve found that Jekyll doesn’t seem to be collecting categories from content that isn’t a ‘post’.

I followed through the tutorial, then added categories to all the content (the 3 posts and 2 staff pages).

I then iterate over site.categories , but it only outputs categories that are defined in ‘post’ content. Categories that are included in the ‘authors’ content don’t seem to be added to the site.categories collection.

Is there some flag that I’m missing that would enable categories in non-post collections? I wasn’t able to find anything in the documentation, and most search results talk about assigning tags and categories to posts - not different page types.

Example site that illustrates this is here.

Thanks in advance.

This is a limitation with Jekyll.
Currently, you’ll have to use a plugin to iterate through categories from content other than posts.

Try jekyll-tagories if you’re on a recent version of Jekyll and provide feedback. It will not be merged into Jekyll Core until the next major version so that users can opt-in to using the functionality and allow refining them till it becomes a core feature.