Avoid running success results after end_line

[sullyvannunes]

This PR introduces the concept of End Line to address issue #14. End Line is intended to be a playful term that evokes the Railway.

The method and_then checks whether the current result is an End Line rather than solely checking for failure.

When to Set End Line for a Result?

• Failure is always treated as an End Line. Therefore, it doesn`t alter the behavior for failures.

• Success is considered an End Line if and only if a Continue result produces a Success result. Consequently, the and_then method will not execute blocks for success results marked as End Line, returning the first Success found after a Continue. For example:

class BCDD::Result::Context::AndThenWithSubjectContinueFollowedBySuccessResultsSingletonTest < Minitest::Test
  module ContinuedFollowedBySuccessResults
    extend self, BCDD::Result.mixin(with: :Continue)

    def call
      Continue(value: 0)
        .and_then { Success(:first_success, value: 1) }
        .and_then { Success(:second_success, value: 2) }
    end
  end

  test 'Method chain interrupts after the first Success' do
    success = ContinuedFollowedBySuccessResults.call

    assert_predicate success, :success?
    assert_equal :first_success, success.type
    assert_equal({ value: 1 }, success.value)
  end
end

To-Do

• Discuss whether it makes sense to raise an error when attempting to execute and_then blocks and methods inSuccess End Line. Otherwise, debugging a long and_then chain may become challenging.
• Update the documentation in accordance with the previous discussion.

[serradura]

@sullyvannunes, thank you for your contribution!

The last release (which introduced the BCDD::Result::Config changed the structure and made it challenging to reuse what you proposed. Because of this, I decided to implement the feature from scratch in a new branch (#17). And as it was merged, I'll close your PR.

Thank you again for your time and interest in contributing to the gem!