class RuboCop::Cop::Style::InverseMethods

This cop check for usages of not (`not` or `!`) called on a method when an inverse of that method can be used instead. Methods that can be inverted by a not (`not` or `!`) should be defined in `InverseMethods` Methods that are inverted by inverting the return of the block that is passed to the method should be defined in `InverseBlocks`

@example

# bad
!foo.none?
!foo.any? { |f| f.even? }
!foo.blank?
!(foo == bar)
foo.select { |f| !f.even? }
foo.reject { |f| f != 7 }

# good
foo.none?
foo.blank?
foo.any? { |f| f.even? }
foo != bar
foo == bar
!!('foo' =~ /^\w+$/)
!(foo.class < Numeric) # Checking class hierarchy is allowed
# Blocks with guard clauses are ignored:
foo.select do |f|
  next if f.zero?
  f != 1
end

Constants

CAMEL_CASE
CLASS_COMPARISON_METHODS
EQUALITY_METHODS
MSG
NEGATED_EQUALITY_METHODS

Public Class Methods

autocorrect_incompatible_with() click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 46
def self.autocorrect_incompatible_with
  [Style::Not]
end

Public Instance Methods

autocorrect(node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 96
def autocorrect(node)
  method_call, _lhs, method, _rhs = inverse_candidate?(node)

  if method_call && method
    lambda do |corrector|
      corrector.remove(not_to_receiver(node, method_call))
      corrector.replace(method_call.loc.selector,
                        inverse_methods[method].to_s)

      if EQUALITY_METHODS.include?(method)
        corrector.remove(end_parentheses(node, method_call))
      end
    end
  else
    correct_inverse_block(node)
  end
end
correct_inverse_block(node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 114
def correct_inverse_block(node)
  method_call, method, block = inverse_block?(node)

  lambda do |corrector|
    corrector.replace(method_call.loc.selector,
                      inverse_blocks[method].to_s)
    correct_inverse_selector(block, corrector)
  end
end
correct_inverse_selector(block, corrector) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 124
def correct_inverse_selector(block, corrector)
  selector = block.loc.selector.source

  if NEGATED_EQUALITY_METHODS.include?(selector.to_sym)
    selector[0] = '='
    corrector.replace(block.loc.selector, selector)
  else
    if block.loc.dot
      range = dot_range(block.loc)
      corrector.remove(range)
    end

    corrector.remove(block.loc.selector)
  end
end
on_block(node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 80
def on_block(node)
  inverse_block?(node) do |_method_call, method, block|
    return unless inverse_blocks.key?(method)
    return if negated?(node) && negated?(node.parent)
    return if node.each_node(:next).any?

    # Inverse method offenses inside of the block of an inverse method
    # offense, such as `y.reject { |key, _value| !(key =~ /c\d/) }`,
    # can cause auto-correction to apply improper corrections.
    ignore_node(block)
    add_offense(node,
                message: format(MSG, method: method,
                                     inverse: inverse_blocks[method]))
  end
end
on_send(node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 66
def on_send(node)
  return if part_of_ignored_node?(node)

  inverse_candidate?(node) do |_method_call, lhs, method, rhs|
    return unless inverse_methods.key?(method)
    return if possible_class_hierarchy_check?(lhs, rhs, method)
    return if negated?(node)

    add_offense(node,
                message: format(MSG, method: method,
                                     inverse: inverse_methods[method]))
  end
end

Private Instance Methods

camel_case_constant?(node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 177
def camel_case_constant?(node)
  node.const_type? && node.source =~ CAMEL_CASE
end
dot_range(loc) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 181
def dot_range(loc)
  range_between(loc.dot.begin_pos, loc.expression.end_pos)
end
end_parentheses(node, method_call) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 162
def end_parentheses(node, method_call)
  Parser::Source::Range.new(node.loc.expression.source_buffer,
                            method_call.loc.expression.end_pos,
                            node.loc.expression.end_pos)
end
inverse_blocks() click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 147
def inverse_blocks
  @inverse_blocks ||= cop_config['InverseBlocks']
                      .merge(cop_config['InverseBlocks'].invert)
end
inverse_methods() click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 142
def inverse_methods
  @inverse_methods ||= cop_config['InverseMethods']
                       .merge(cop_config['InverseMethods'].invert)
end
negated?(node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 152
def negated?(node)
  node.parent.respond_to?(:method?) && node.parent.method?(:!)
end
not_to_receiver(node, method_call) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 156
def not_to_receiver(node, method_call)
  Parser::Source::Range.new(node.loc.expression.source_buffer,
                            node.loc.selector.begin_pos,
                            method_call.loc.expression.begin_pos)
end
possible_class_hierarchy_check?(lhs, rhs, method) click to toggle source

When comparing classes, `!(Integer < Numeric)` is not the same as `Integer > Numeric`.

# File lib/rubocop/cop/style/inverse_methods.rb, line 170
def possible_class_hierarchy_check?(lhs, rhs, method)
  CLASS_COMPARISON_METHODS.include?(method) &&
    (camel_case_constant?(lhs) ||
     (rhs.size == 1 &&
      camel_case_constant?(rhs.first)))
end