struct_inheritance_spec.rb

# frozen_string_literal: true

RSpec.describe RuboCop::Cop::Style::StructInheritance do
  subject(:cop) { described_class.new }

  it 'registers an offense when extending instance of Struct' do
    expect_offense(<<~RUBY)
      class Person < Struct.new(:first_name, :last_name)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Don't extend an instance initialized by `Struct.new`. Use a block to customize the struct.
        def foo; end
      end
    RUBY

    expect_correction(<<~RUBY)
      Person = Struct.new(:first_name, :last_name) do
        def foo; end
      end
    RUBY
  end

  it 'registers an offense when extending instance of Struct with do ... end' do
    expect_offense(<<~RUBY)
      class Person < Struct.new(:first_name, :last_name) do end
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Don't extend an instance initialized by `Struct.new`. Use a block to customize the struct.
      end
    RUBY

    expect_correction(<<~RUBY)
      Person = Struct.new(:first_name, :last_name) do
      end
    RUBY
  end

  it 'accepts plain class' do
    expect_no_offenses(<<~RUBY)
      class Person
      end
    RUBY
  end

  it 'accepts extending DelegateClass' do
    expect_no_offenses(<<~RUBY)
      class Person < DelegateClass(Animal)
      end
    RUBY
  end

  it 'accepts assignment to Struct.new' do
    expect_no_offenses('Person = Struct.new(:first_name, :last_name)')
  end

  it 'accepts assignment to block form of Struct.new' do
    expect_no_offenses(<<~RUBY)
      Person = Struct.new(:first_name, :last_name) do
        def age
          42
        end
      end
    RUBY
  end
end