Added

• New extension for RSpec (@flash-gordon in #183): One of the pain points of testing monads is referencing class constants from specs. This extension catches missing class constants, analyzes the call site and returns a matching constant.

  Before, this code would raise a NameError because Failure is a constant that is missing in Object:

  example "missing constant" do
    expect(call_operation).to eql(Failure[:some_error, "some message"])
  end
  

  Now, after enabling the extension, it will return the correct constant:

  Dry::Monads.load_extensions(:rspec)
  
  example "missing constant" do
    Failure[:some_error, "some message"] # => Failure[:some_error, "some message"]
  end
  

  Out of the box, the extension will check if Success, Failure, Some, and None are referenced from a file ending with _spec.rb.

  More involved analysis is possible if you add debug_inspector to your Gemfile:

  group :test do
    gem "debug_inspector"
  end
  

  This will allow referencing constants from other modules, such as rspec helpers.

  The extension also adds new matchers for Success, Failure, Some, and None values.

  expect(Success(1)).to be_success
  expect(Success(1)).to be_success(1)
  expect(Success(1)).to be_success { |x| x > 0 }
  expect(Success(1)).to be_a_success { |x| x > 0 }
  
  expect(Failure(1)).to be_failure(1)
  
  expect(Some(1)).to be_some
  expect(Some(1)).to be_success
  
  expect(None()).to be_none
  expect(None()).to be_failure
  

• New extension for super_diff (@flash-gordon in #184):

  Adds support for improved diff output in specs when using the super_diff gem. This makes it easier to understand the differences between monad values in test failures.

  To use this extension:

  1. Add super_diff to your Gemfile's test group:

     group :test do
       gem "super_diff"
     end
     

  2. Load the extension:

     require "dry/monads"
     Dry::Monads.load_extensions(:super_diff)
     

  This will change the diff output for monad values to be more readable.

  Before:

  -Success({a: 2, c: 2})
  +Success({a: 1, b: 2})
  

  After:

  Success(
  -   a: 2,
  +   a: 1,
  -   c: 2
  +   b: 2
  )
  

Compare v1.7.1...v1.8.0