qwe.rb

require "dry-validation"

schema = Dry::Validation.Schema do
  optional(:vin).maybe(:str?)
  optional(:chassis_number).maybe(:str?)
  optional(:engine_number).maybe(:str?)
  optional(:body_number).maybe(:str?)

  rule(numbers_presense: [:vin, :chassis_number, :engine_number, :body_number]) do |vin, chassis_number, engine_number, body_number|
    vin.filled? | (engine_number.filled? & (chassis_number.filled? | body_number.filled?))
  end
end

schema.call(vin: nil, engine_number: "qweqwe", chassis_number: "qweqwe")
# => #<Dry::Validation::Result output={:vin=>nil, :engine_number=>"qweqwe", :chassis_number=>"qweqwe"} errors={}>
schema.call(vin: nil, engine_number: "qweqwe", body_number: "qweqwe")
# => #<Dry::Validation::Result output={:vin=>nil, :engine_number=>"qweqwe", :body_number=>"qweqwe"} errors={}>
schema.call(vin: nil, engine_number: nil, body_number: "qweqwe")
# => #<Dry::Validation::Result output={:vin=>nil, :engine_number=>nil, :body_number=>"qweqwe"} errors={:numbers_presense=>["must be filled"]}>
schema.call(vin: "qweqweq", engine_number: nil, body_number: "qweqwe")
# => #<Dry::Validation::Result output={:vin=>"qweqweq", :engine_number=>nil, :body_number=>"qweqwe"} errors={}>