module RSpec::Core::MemoizedHelpers

@private

# File rspec-core/lib/rspec/core/memoized_helpers.rb, line 542
def self.define_helpers_on(example_group)
  example_group.__send__(:include, module_for(example_group))
end

@private

Gets the named constant or yields. On 1.8, const_defined? / const_get do not take into account the inheritance hierarchy. :nocov:

# File rspec-core/lib/rspec/core/memoized_helpers.rb, line 553
def self.get_constant_or_yield(example_group, name)
  if example_group.const_defined?(name)
    example_group.const_get(name)
  else
    yield
  end
end

@private

Gets the LetDefinitions module. The module is mixed into the example group and is used to hold all let definitions. This is done so that the block passed to ‘let` can be forwarded directly on to `define_method`, so that all method constructs (including `super` and `return`) can be used in a `let` block.

The memoization is provided by a method definition on the example group that supers to the LetDefinitions definition in order to get the value to memoize.

# File rspec-core/lib/rspec/core/memoized_helpers.rb, line 528
def self.module_for(example_group)
  get_constant_or_yield(example_group, :LetDefinitions) do
    mod = Module.new do
      include(Module.new {
        example_group.const_set(:NamedSubjectPreventSuper, self)
      })
    end

    example_group.const_set(:LetDefinitions, mod)
    mod
  end
end

@private

# File rspec-core/lib/rspec/core/memoized_helpers.rb, line 135
def initialize(*)
  __init_memoized
  super
end

Wraps the ‘subject` in `expect` to make it the target of an expectation. Designed to read nicely for one-liners.

@example

describe [1, 2, 3] do
  it { is_expected.to be_an Array }
  it { is_expected.not_to include 4 }
end

@see subject @see should @see should_not

@note This only works if you are using rspec-expectations.

# File rspec-core/lib/rspec/core/memoized_helpers.rb, line 120
def is_expected
  expect(subject)
end

When ‘should` is called with no explicit receiver, the call is delegated to the object returned by `subject`. Combined with an implicit subject this supports very concise expressions.

@example

RSpec.describe Person do
  it { should be_eligible_to_vote }
end

@see subject @see is_expected

@note This only works if you are using rspec-expectations. @note If you are using RSpec’s newer expect-based syntax you may

want to use `is_expected.to` instead of `should`.

# File rspec-core/lib/rspec/core/memoized_helpers.rb, line 80
def should(matcher=nil, message=nil)
  enforce_value_expectation(matcher, 'should')
  RSpec::Expectations::PositiveExpectationHandler.handle_matcher(subject, matcher, message)
end

Just like ‘should`, `should_not` delegates to the subject (implicit or explicit) of the example group.

@example

RSpec.describe Person do
  it { should_not be_eligible_to_vote }
end

@see subject @see is_expected

@note This only works if you are using rspec-expectations. @note If you are using RSpec’s newer expect-based syntax you may

want to use `is_expected.to_not` instead of `should_not`.

# File rspec-core/lib/rspec/core/memoized_helpers.rb, line 100
def should_not(matcher=nil, message=nil)
  enforce_value_expectation(matcher, 'should_not')
  RSpec::Expectations::NegativeExpectationHandler.handle_matcher(subject, matcher, message)
end

@note ‘subject` was contributed by Joe Ferris to support the one-liner

syntax embraced by shoulda matchers:

    RSpec.describe Widget do
      it { is_expected.to validate_presence_of(:name) }
      # or
      it { should validate_presence_of(:name) }
    end

While the examples below demonstrate how to use `subject`
explicitly in examples, we recommend that you define a method with
an intention revealing name instead.

@example

# Explicit declaration of subject.
RSpec.describe Person do
  subject { Person.new(:birthdate => 19.years.ago) }
  it "should be eligible to vote" do
    subject.should be_eligible_to_vote
    # ^ ^ explicit reference to subject not recommended
  end
end

# Implicit subject => { Person.new }.
RSpec.describe Person do
  it "should be eligible to vote" do
    subject.should be_eligible_to_vote
    # ^ ^ explicit reference to subject not recommended
  end
end

# One-liner syntax - expectation is set on the subject.
RSpec.describe Person do
  it { is_expected.to be_eligible_to_vote }
  # or
  it { should be_eligible_to_vote }
end

@note Because ‘subject` is designed to create state that is reset

between each example, and `before(:context)` is designed to setup
state that is shared across _all_ examples in an example group,
`subject` is _not_ intended to be used in a `before(:context)` hook.

@see should @see should_not @see is_expected

# File rspec-core/lib/rspec/core/memoized_helpers.rb, line 57
def subject
  __memoized.fetch_or_store(:subject) do
    described = described_class || self.class.metadata.fetch(:description_args).first
    Class === described ? described.new : described
  end
end