Using org-roam tags when org publishing

Question

When publishing it's possible to get a list of filetags for an org note by doing something like (org-export-data (plist-get info :filetags) info) in publish.el and loop over them to create markup. I use org-roam and was wondering if there is a way to do something similar with the +#roam_tags: property. Just switching :filetags for :roam_tags doesn't work - no error, it's just empty I think. Could anyone offer some advice on how I might approach this?

FYI I asked this question on the org-mode sub reddit as well but posting here as well.

Answer 1

After experimenting with custom backends using org-export-define-derived-backend, I learned that we can define custom properties and reference their values in the way my question states. For example:

We can derive a backend from the existing one and provide customizations. In this case, we can define a custom property mapped to the export property.

(org-export-define-derived-backend 'my-custom-backend 'slimhtml
  :options-alist
  '((:roam_tags "ROAM_TAGS" nil nil split)))

Now, with my-custom-backend defined, invoking (plist-get info :roam_tags) returns a list of the #+roam_tags. Also, we can access the roam tags with (org-publish-find-property entry :roam_tags project 'my-custom-backend)

See https://orgmode.org/worg/dev/org-export-reference.html and http://doc.endlessparentheses.com/Var/org-export-options-alist.html for more details like the additional arguments.