class RuboCop::Cop::Style::InvertibleUnlessCondition

Checks for usages of ‘unless` which can be replaced by `if` with inverted condition. Code without `unless` is easier to read, but that is subjective, so this cop is disabled by default.

Methods that can be inverted should be defined in ‘InverseMethods`. Note that the relationship of inverse methods needs to be defined in both directions. For example,

source,yaml

InverseMethods:

:!=: :==
:even?: :odd?
:odd?: :even?

will suggest both ‘even?` and `odd?` to be inverted, but only `!=` (and not `==`).

@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 (simple condition)
foo unless !bar
foo unless x != y
foo unless x >= 10
foo unless x.even?
foo unless odd?

# good
foo if bar
foo if x == y
foo if x < 10
foo if x.odd?
foo if even?

# bad (complex condition)
foo unless x != y || x.even?

# good
foo if x == y && x.odd?

# good (if)
foo if !condition

Constants

MSG

Public Instance Methods

on_if(node) click to toggle source
# File lib/rubocop/cop/style/invertible_unless_condition.rb, line 58
def on_if(node)
  return unless node.unless?

  condition = node.condition
  return unless invertible?(condition)

  message = format(MSG, prefer: "#{node.inverse_keyword} #{preferred_condition(condition)}",
                        current: "#{node.keyword} #{condition.source}")

  add_offense(node, message: message) do |corrector|
    corrector.replace(node.loc.keyword, node.inverse_keyword)
    autocorrect(corrector, condition)
  end
end

Private Instance Methods

autocorrect(corrector, node) click to toggle source
# File lib/rubocop/cop/style/invertible_unless_condition.rb, line 133
def autocorrect(corrector, node)
  case node.type
  when :begin
    autocorrect(corrector, node.children.first)
  when :send
    autocorrect_send_node(corrector, node)
  when :or, :and
    corrector.replace(node.loc.operator, node.inverse_operator)
    autocorrect(corrector, node.lhs)
    autocorrect(corrector, node.rhs)
  end
end
autocorrect_send_node(corrector, node) click to toggle source
# File lib/rubocop/cop/style/invertible_unless_condition.rb, line 146
def autocorrect_send_node(corrector, node)
  if node.method?(:!)
    corrector.remove(node.loc.selector)
  else
    corrector.replace(node.loc.selector, inverse_methods[node.method_name])
  end
end
inheritance_check?(node) click to toggle source
# File lib/rubocop/cop/style/invertible_unless_condition.rb, line 90
def inheritance_check?(node)
  argument = node.first_argument
  node.method?(:<) &&
    (argument.const_type? && argument.short_name.to_s.upcase != argument.short_name.to_s)
end
inverse_methods() click to toggle source
# File lib/rubocop/cop/style/invertible_unless_condition.rb, line 154
def inverse_methods
  @inverse_methods ||= cop_config['InverseMethods']
end
invertible?(node) click to toggle source
# File lib/rubocop/cop/style/invertible_unless_condition.rb, line 75
def invertible?(node) # rubocop:disable Metrics/CyclomaticComplexity
  case node&.type
  when :begin
    invertible?(node.children.first)
  when :send
    return false if inheritance_check?(node)

    node.method?(:!) || inverse_methods.key?(node.method_name)
  when :or, :and
    invertible?(node.lhs) && invertible?(node.rhs)
  else
    false
  end
end
preferred_condition(node) click to toggle source
# File lib/rubocop/cop/style/invertible_unless_condition.rb, line 96
def preferred_condition(node)
  case node.type
  when :begin    then "(#{preferred_condition(node.children.first)})"
  when :send     then preferred_send_condition(node)
  when :or, :and then preferred_logical_condition(node)
  end
end
preferred_logical_condition(node) click to toggle source
# File lib/rubocop/cop/style/invertible_unless_condition.rb, line 126
def preferred_logical_condition(node)
  preferred_lhs = preferred_condition(node.lhs)
  preferred_rhs = preferred_condition(node.rhs)

  "#{preferred_lhs} #{node.inverse_operator} #{preferred_rhs}"
end
preferred_send_condition(node) click to toggle source
# File lib/rubocop/cop/style/invertible_unless_condition.rb, line 104
def preferred_send_condition(node) # rubocop:disable Metrics/CyclomaticComplexity
  receiver_source = node.receiver&.source
  return receiver_source if node.method?(:!)

  # receiver may be implicit (self)
  dotted_receiver_source = receiver_source ? "#{receiver_source}." : ''

  inverse_method_name = inverse_methods[node.method_name]
  return "#{dotted_receiver_source}#{inverse_method_name}" unless node.arguments?

  argument_list = node.arguments.map(&:source).join(', ')
  if node.operator_method?
    return "#{receiver_source} #{inverse_method_name} #{argument_list}"
  end

  if node.parenthesized?
    return "#{dotted_receiver_source}#{inverse_method_name}(#{argument_list})"
  end

  "#{dotted_receiver_source}#{inverse_method_name} #{argument_list}"
end