rails/rails — pull request #14192 by acapilleri (2014-02-25 10:59:49+00:00)
Title: added `ArgumentExcpetion` if `validates` has duplicated attributes.

Currently you can pass duplicated attributes as argument to `valitates` methods.

Example:

Person.validates_presence_of :name, :name
person = Person.new

# before
person.valid?
person.errors.size #=> 2

# with this pr
person.valid? #=> `ArgumentError Exception`