class RuboCop::Cop::Style::ClassEqualityComparison

Enforces the use of ‘Object#instance_of?` instead of class comparison for equality. `==`, `equal?`, and `eql?` custom method definitions are allowed by default. These are customizable with `AllowedMethods` option.

@safety

This cop's autocorrection is unsafe because there is no guarantee that
the constant `Foo` exists when autocorrecting `var.class.name == 'Foo'` to
`var.instance_of?(Foo)`.

@example

# bad
var.class == Date
var.class.equal?(Date)
var.class.eql?(Date)
var.class.name == 'Date'

# good
var.instance_of?(Date)

@example AllowedMethods: [‘==’, ‘equal?’, ‘eql?’] (default)

# good
def ==(other)
  self.class == other.class && name == other.name
end

def equal?(other)
  self.class.equal?(other.class) && name.equal?(other.name)
end

def eql?(other)
  self.class.eql?(other.class) && name.eql?(other.name)
end

@example AllowedPatterns: [] (default)

# bad
def eq(other)
  self.class.eq(other.class) && name.eq(other.name)
end

@example AllowedPatterns: [‘eq’]

# good
def eq(other)
  self.class.eq(other.class) && name.eq(other.name)
end

Constants

CLASS_NAME_METHODS
MSG
RESTRICT_ON_SEND

Public Instance Methods

on_send(node) click to toggle source
# File lib/rubocop/cop/style/class_equality_comparison.rb, line 70
def on_send(node)
  def_node = node.each_ancestor(:def, :defs).first
  return if def_node &&
            (allowed_method?(def_node.method_name) ||
            matches_allowed_pattern?(def_node.method_name))

  class_comparison_candidate?(node) do |receiver_node, class_node|
    return if class_node.dstr_type?

    range = offense_range(receiver_node, node)
    class_argument = (class_name = class_name(class_node, node)) ? "(#{class_name})" : ''

    add_offense(range, message: format(MSG, class_argument: class_argument)) do |corrector|
      next unless class_name

      corrector.replace(range, "instance_of?#{class_argument}")
    end
  end
end

Private Instance Methods

class_name(class_node, node) click to toggle source
# File lib/rubocop/cop/style/class_equality_comparison.rb, line 92
def class_name(class_node, node)
  if class_name_method?(node.children.first.method_name)
    if (receiver = class_node.receiver) && class_name_method?(class_node.method_name)
      return receiver.source
    end

    if class_node.str_type?
      value = trim_string_quotes(class_node)
      value.prepend('::') if require_cbase?(class_node)
      return value
    elsif unable_to_determine_type?(class_node)
      # When a variable or return value of a method is used, it returns nil
      # because the type is not known and cannot be suggested.
      return
    end
  end

  class_node.source
end
class_name_method?(method_name) click to toggle source
# File lib/rubocop/cop/style/class_equality_comparison.rb, line 112
def class_name_method?(method_name)
  CLASS_NAME_METHODS.include?(method_name)
end
offense_range(receiver_node, node) click to toggle source
# File lib/rubocop/cop/style/class_equality_comparison.rb, line 128
def offense_range(receiver_node, node)
  range_between(receiver_node.loc.selector.begin_pos, node.source_range.end_pos)
end
require_cbase?(class_node) click to toggle source
# File lib/rubocop/cop/style/class_equality_comparison.rb, line 116
def require_cbase?(class_node)
  class_node.each_ancestor(:class, :module).any?
end
trim_string_quotes(class_node) click to toggle source
# File lib/rubocop/cop/style/class_equality_comparison.rb, line 124
def trim_string_quotes(class_node)
  class_node.source.delete('"').delete("'")
end
unable_to_determine_type?(class_node) click to toggle source
# File lib/rubocop/cop/style/class_equality_comparison.rb, line 120
def unable_to_determine_type?(class_node)
  class_node.variable? || class_node.call_type?
end