class RuboCop::Cop::Style::InverseMethods

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`.

@safety

This cop is unsafe because it cannot be guaranteed that the method
and its inverse method are both defined on receiver, and also are
actually inverse of each other.

@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
RESTRICT_ON_SEND

Public Class Methods

autocorrect_incompatible_with() click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 56
def self.autocorrect_incompatible_with
  [Style::Not, Style::SymbolProc]
end

Public Instance Methods

on_block(node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 92
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 autocorrection to apply improper corrections.
    ignore_node(block)
    add_offense(node, message: message(method, inverse_blocks[method])) do |corrector|
      correct_inverse_block(corrector, node)
    end
  end
end
Also aliased as: on_numblock
on_csend(node)
Alias for: on_send
on_numblock(node)
Alias for: on_block
on_send(node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 78
def on_send(node)
  inverse_candidate?(node) do |method_call, lhs, method, rhs|
    return unless inverse_methods.key?(method)
    return if negated?(node) || relational_comparison_with_safe_navigation?(method_call)
    return if part_of_ignored_node?(node)
    return if possible_class_hierarchy_check?(lhs, rhs, method)

    add_offense(node, message: message(method, inverse_methods[method])) do |corrector|
      correct_inverse_method(corrector, node)
    end
  end
end
Also aliased as: on_csend

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? && CAMEL_CASE.match?(node.source)
end
correct_inverse_block(corrector, node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 121
def correct_inverse_block(corrector, node)
  method_call, method, block = inverse_block?(node)

  corrector.replace(method_call.loc.selector, inverse_blocks[method].to_s)
  correct_inverse_selector(block, corrector)
end
correct_inverse_method(corrector, node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 112
def correct_inverse_method(corrector, node)
  method_call, _lhs, method, _rhs = inverse_candidate?(node)
  return unless method_call && method

  corrector.remove(not_to_receiver(node, method_call))
  corrector.replace(method_call.loc.selector, inverse_methods[method].to_s)
  remove_end_parenthesis(corrector, node, method, method_call)
end
correct_inverse_selector(block, corrector) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 128
def correct_inverse_selector(block, corrector)
  selector_loc = block.loc.selector
  selector = selector_loc.source

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

    corrector.remove(selector_loc)
  end
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 166
def end_parentheses(node, method_call)
  method_call.source_range.end.join(node.source_range.end)
end
inverse_blocks() click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 150
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 145
def inverse_methods
  @inverse_methods ||= cop_config['InverseMethods']
                       .merge(cop_config['InverseMethods'].invert)
end
message(method, inverse) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 191
def message(method, inverse)
  format(MSG, method: method, inverse: inverse)
end
negated?(node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 154
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 162
def not_to_receiver(node, method_call)
  node.loc.selector.begin.join(method_call.source_range.begin)
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 172
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
relational_comparison_with_safe_navigation?(node) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 158
def relational_comparison_with_safe_navigation?(node)
  node.csend_type? && CLASS_COMPARISON_METHODS.include?(node.method_name)
end
remove_end_parenthesis(corrector, node, method, method_call) click to toggle source
# File lib/rubocop/cop/style/inverse_methods.rb, line 185
def remove_end_parenthesis(corrector, node, method, method_call)
  return unless EQUALITY_METHODS.include?(method) || method_call.parent.begin_type?

  corrector.remove(end_parentheses(node, method_call))
end