module RSpec::Matchers::DSL::Macros

Convenience for defining methods on this matcher to create a fluent interface. The trick about fluent interfaces is that each method must return self in order to chain methods together. ‘chain` handles that for you. If the method is invoked and the `include_chain_clauses_in_custom_matcher_descriptions` config option hash been enabled, the chained method name and args will be added to the default description and failure message.

In the common case where you just want the chained method to store some value(s) for later use (e.g. in ‘match`), you can provide one or more attribute names instead of a block; the chained method will store its arguments in instance variables with those names, and the values will be exposed via getters.

@example

RSpec::Matchers.define :have_errors_on do |key|
  chain :with do |message|
    @message = message
  end

  match do |actual|
    actual.errors[key] == @message
  end
end

expect(minor).to have_errors_on(:age).with("Not old enough to participate")

# File rspec-expectations/lib/rspec/matchers/dsl.rb, line 298
def chain(method_name, *attr_names, &definition)
  unless block_given? ^ attr_names.any?
    raise ArgumentError, "You must pass either a block or some attribute names (but not both) to `chain`."
  end

  definition = assign_attributes(attr_names) if attr_names.any?

  define_user_override(method_name, definition) do |*args, &block|
    super(*args, &block)
    @chained_method_clauses.push([method_name, args])
    self
  end
end

Customize the description to use for one-liners. Only use this when the description generated by default doesn’t suit your needs.

@example

RSpec::Matchers.define :qualify_for do |expected|
  match { your_match_logic }

  description do
    "qualify for #{expected}"
  end
end

@yield [Object] actual the actual object (i.e. the value wrapped by ‘expect`)

# File rspec-expectations/lib/rspec/matchers/dsl.rb, line 253
def description(&definition)
  define_user_override(__method__, definition)
end

Tells the matcher to diff the actual and expected values in the failure message.

# File rspec-expectations/lib/rspec/matchers/dsl.rb, line 259
def diffable
  define_method(:diffable?) { true }
end

Customizes the failure message to use when this matcher is asked to positively match. Only use this when the message generated by default doesn’t suit your needs.

@example

RSpec::Matchers.define :have_strength do |expected|
  match { your_match_logic }

  failure_message do |actual|
    "Expected strength of #{expected}, but had #{actual.strength}"
  end
end

@yield [Object] actual the actual object (i.e. the value wrapped by ‘expect`)

# File rspec-expectations/lib/rspec/matchers/dsl.rb, line 216
def failure_message(&definition)
  define_user_override(__method__, definition)
end

Customize the failure message to use when this matcher is asked to negatively match. Only use this when the message generated by default doesn’t suit your needs.

@example

RSpec::Matchers.define :have_strength do |expected|
  match { your_match_logic }

  failure_message_when_negated do |actual|
    "Expected not to have strength of #{expected}, but did"
  end
end

@yield [Object] actual the actual object (i.e. the value wrapped by ‘expect`)

# File rspec-expectations/lib/rspec/matchers/dsl.rb, line 235
def failure_message_when_negated(&definition)
  define_user_override(__method__, definition)
end

Stores the block that is used to determine whether this matcher passes or fails. The block should return a boolean value. When the matcher is passed to ‘expect(…).to` and the block returns `true`, then the expectation passes. Similarly, when the matcher is passed to `expect(…).not_to` and the block returns `false`, then the expectation passes.

@example

RSpec::Matchers.define :be_even do
  match do |actual|
    actual.even?
  end
end

expect(4).to be_even     # passes
expect(3).not_to be_even # passes
expect(3).to be_even     # fails
expect(4).not_to be_even # fails

By default the match block will swallow expectation errors (e.g. caused by using an expectation such as ‘expect(1).to eq 2`), if you wish to allow these to bubble up, pass in the option `:notify_expectation_failures => true`.

@param [Hash] options for defining the behavior of the match block. @yield [Object] actual the actual value (i.e. the value wrapped by ‘expect`)

# File rspec-expectations/lib/rspec/matchers/dsl.rb, line 131
def match(options={}, &match_block)
  define_user_override(:matches?, match_block) do |actual|
    @actual = actual
    RSpec::Support.with_failure_notifier(RAISE_NOTIFIER) do
      begin
        super(*actual_arg_for(match_block))
      rescue RSpec::Expectations::ExpectationNotMetError
        raise if options[:notify_expectation_failures]
        false
      end
    end
  end
end

Use this instead of ‘match` when the block will raise an exception rather than returning false to indicate a failure.

@example

RSpec::Matchers.define :accept_as_valid do |candidate_address|
  match_unless_raises ValidationException do |validator|
    validator.validate(candidate_address)
  end
end

expect(email_validator).to accept_as_valid("person@company.com")

@yield [Object] actual the actual object (i.e. the value wrapped by ‘expect`)

# File rspec-expectations/lib/rspec/matchers/dsl.rb, line 188
def match_unless_raises(expected_exception=Exception, &match_block)
  define_user_override(:matches?, match_block) do |actual|
    @actual = actual
    begin
      super(*actual_arg_for(match_block))
    rescue expected_exception => @rescued_exception
      false
    else
      true
    end
  end
end

Use this to define the block for a negative expectation (‘expect(…).not_to`) when the positive and negative forms require different handling. This is rarely necessary, but can be helpful, for example, when specifying asynchronous processes that require different timeouts.

By default the match block will swallow expectation errors (e.g. caused by using an expectation such as ‘expect(1).to eq 2`), if you wish to allow these to bubble up, pass in the option `:notify_expectation_failures => true`.

@param [Hash] options for defining the behavior of the match block. @yield [Object] actual the actual value (i.e. the value wrapped by ‘expect`)

# File rspec-expectations/lib/rspec/matchers/dsl.rb, line 160
def match_when_negated(options={}, &match_block)
  define_user_override(:does_not_match?, match_block) do |actual|
    begin
      @actual = actual
      RSpec::Support.with_failure_notifier(RAISE_NOTIFIER) do
        super(*actual_arg_for(match_block))
      end
    rescue RSpec::Expectations::ExpectationNotMetError
      raise if options[:notify_expectation_failures]
      false
    end
  end
end

Declares that the matcher can be used in a block expectation. Users will not be able to use your matcher in a block expectation without declaring this. (e.g. ‘expect { do_something }.to matcher`).

# File rspec-expectations/lib/rspec/matchers/dsl.rb, line 267
def supports_block_expectations
  define_method(:supports_block_expectations?) { true }
end