I've got an issue with validations on aliased fields and I'm not sure whether it's an issue with Mongoid or maybe ActiveModel. Tested with Mongoid master, Rails 4 RC1, RC2 and final.

class Page
include Mongoid::Document

field :h, as: :hidden, type: Boolean, default: false
validates :hidden, inclusion:

end

When I use form helpers in my views that use the alias name, e.g.

<%= f.check_box :hidden %>

I always get the validation error 'Hidden is not included in the list', even though the checkbox value shows up correctly in the params as a value that should be treated as boolean.

If I use the form helper on the original field name, it passes validation:

<%= f.check_box :h %>

Is that intended behaviour? It only seems to be an issue with form helpers, when I manually set the fields on objects it works fine no matter if I set the aliased name or the original, e.g.

page.h = "1"

will be valid just like

page.hidden = "1"