Summary of Changes

Since introduced in 2010, the FormHelper class has always had a note about how the pluralization logic for form entity types should use a proper inflector, but it never being a big deal because our core API "only" supports entity types that are pluralized by tacking the letter S onto a word (field and rule). We have had an inflector in our API since 2011. It's 2018, I think we can use the inflector now.

Testing Instructions

There should be no practical change here really. Form fields and rules registered through path lookups should keep working. If you actually have a custom Form API entity type, and its pluralization doesn't follow the simple "add S to word" (lets just say entity for the sake of discussion since right now the code would make that "entitys" for the path name when it should be "entities" following correct language rules), the incorrect spelling is deprecated and should raise a log notice (though to be honest the odds of this code path ever being triggered are going to be slim to none).