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?

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

# 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 56
def on_if(node)
  return unless node.unless?

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

  add_offense(node) 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 91
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 104
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 85
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 112
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 70
def invertible?(node)
  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