For some reason, Grails decided to delete their published list of all validation constraints. This official-sounding page just sends you to the reference docs, and its validation page gives the unhelpful message that
A complete reference for the available constraints can be found on the reference guide
I’m not sure what other reference guide this could be referring to, not to mention what it would mean for this information to be found “on” the reference guide, as opposed to “in” it.
Update: @mr_paul_woods sent me to the Grails docs and told me to look in the sidebar. Turns out that I wasn’t supposed to click Validation on the right pane, but rather find “Constraints” in the unrelated left pane. There’s no way to get this list on a page by itself, so here they are to be helpful: