gistfile1.txt

module Platform
  module Types
    include Dry::Types.module
    include ROM::Types
    include ROM::SQL::Types
    include ROM::SQL::Types::PG

    # ...

    Phone = String
      .constructor(proc { |value| value.to_s.empty? ? nil : value })
      .constrained(format: /\A([\d]{10}|)\z/).optional
  end
end

Dry::Validation.Form do
  configure do
    config.type_specs = true
  end

  optional(:phone, Platform::Types::Phone).filled
end