Custom predicated in Dry::Struct

1

Hi,

I am working on a tool to create dry struct from an xsd. The xsd has some constraints I would like to mimic. This isn’t it but I simplified the version. Ideally I wanted to add some options to constrained. I looked at the source to constrained source https://github.com/dry-rb/dry-types/blob/2ac0ba485a9c141377151e166861e0e418983495/lib/dry/types/builder.rb#L75-L77 which calls to Rule, which looks up the predicates from Dry::Logic::Predicates https://github.com/dry-rb/dry-types/blob/2ac0ba485a9c141377151e166861e0e418983495/lib/dry/types/constraints.rb#L13-L21. I wouldn’t like to append to that one but I could.

I got a solution working where I create new predicates but use them from a new constructor instead of using constrained. This work but doesn’t give the best errors when multiple constraints fails.

module Types
  include Dry::Types()
  extend Dry::Logic::Builder

  build do
    predicate :divisible_with? do |num, input|
      (input % num).zero?
    end
  end

  divisible_with_ten = build do
    divisible_with?(10)
  end

  LessThenthousend = Integer.constrained(lt: 1000)
  LessThenthousendDivisebleByTen = Types.Constructor(LessThenthousend) { |value, type|
    type.call(value)
      .tap {
        next if divisible_with_ten.call(_1).success?
        raise Dry::Types::ConstraintError.new("divisible_with_ten?", value)
      }
   }
end

# pp Types::LessThenthousend.call(12011)
# :in `call_unsafe': 12000 violates constraints (lt?(1000, 12000) failed) (Dry::Types::ConstraintError)

# pp Types::LessThenthousend.call(120)
# pp Types::LessThenthousendDivisebleByTen.call(121)
# pp Types::LessThenthousendDivisebleByTen.call(12100)

It this how it’s suppose to be done? any suggestions