Dry Transaction Inheritance Repro

example.rb

require 'bundler/inline'

gemfile do
  gem 'dry-validation', '=1.0.0.rc1'
  gem 'dry-transaction', '=0.13.0'
  gem 'minitest', '=5.11.3'
end

require 'dry-validation'
require 'dry/transaction'
require 'minitest/autorun'

# Generilise any API commands
class ApiCommand
  include Dry::Transaction

  def self.build(validate_with:, and_then:)
    Class.new(ApiCommand) do
      def validation_class
        validate_with
      end

      def command_class
        and_then
      end
    end
  end

  def self.handle(params)
    new.call(params)
  end

  step :validate
  step :build_command
  step :execute

  private

  def validate(params)
    result = validation_class.new.call(params)
    result.errors.any? ? Failure(result.errors) : Success(result.to_h)
  end

  def build_command(valid_params)
    Success command_class.new(valid_params)
  end

  def execute(valid_command)
    Success 'yay'
  end
end



class BlogValidator < Dry::Validation::Contract
  params do
    required(:name).filled
  end
end

CreateBlog = Struct.new(:name, keyword_init: true) # in practice - Dry::Struct



# Concrete Api command
class CreateBlogCommandWithInheritance < ApiCommand.build(validate_with: BlogValidator, and_then: CreateBlog)
end


# Same as before logically (but is failing) - copy-paste with no inheritance
class CreateBlogCommandUsualUse
  include Dry::Transaction

  step :validate
  step :build_command
  step :execute

  private

  def validation_class
    BlogValidator
  end

  def command_class
    CreateBlog
  end

  def validate(params)
    result = validation_class.new.call(params)
    result.errors.any? ? Failure(result.errors) : Success(result.to_h)
  end

  def build_command(valid_params)
    Success command_class.new(valid_params)
  end

  def execute(valid_command)
    Success 'yay'
  end
end



class DefinedDirectlyOnAClassAndWorksFine < Minitest::Test
  include Dry::Monads::Result::Mixin

  def test_invalid
    assert_equal({ name: ["must be filled"] }, CreateBlogCommandUsualUse.new.call(name: '').failure.to_h)
  end

  def test_valid
    assert_equal Success('yay'), CreateBlogCommandUsualUse.new.call(name: 'foo')
  end
end

class InheritedAndHasUnexpectedBahviour < Minitest::Test
  include Dry::Monads::Result::Mixin

  def test_invalid
    assert_equal({ name: ["must be filled"] }, CreateBlogCommandWithInheritance.new.call(name: '').failure.to_h)
  end

  def test_valid
    assert_equal Success('yay'), CreateBlogCommandWithInheritance.new.call(name: 'foo')
  end
end

output.txt

# Running:

FF..

Finished in 0.003001s, 1332.8891 runs/s, 1332.8891 assertions/s.

  1) Failure:
InheritedAndHasUnexpectedBahviour#test_invalid [-:120]:
Expected: {:name=>["must be filled"]}
  Actual: {}

  2) Failure:
InheritedAndHasUnexpectedBahviour#test_valid [-:124]:
Expected: Success("yay")
  Actual: Success({:name=>"foo"})

4 runs, 4 assertions, 2 failures, 0 errors, 0 skips