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Class: RuboCop::Cop::Style::ClassEqualityComparison

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::RuboCop::Cop::AutoCorrector, ::RuboCop::Cop::Base, ::RuboCop::ExcludeLimit, NodePattern::Macros, RuboCop::AST::Sexp
Instance Chain:
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/style/class_equality_comparison.rb

Overview

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.

Examples:

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

# good
var.instance_of?(Date)

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

AllowedPatterns: [] (default)

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

AllowedPatterns: ['eq']

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

Cop Safety Information:

  • 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).

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

::RuboCop::Cop::RangeHelp - Included

BYTE_ORDER_MARK, NOT_GIVEN

Class Attribute Summary

::RuboCop::Cop::AutoCorrector - Extended

::RuboCop::Cop::Base - Inherited

.gem_requirements, .lint?,
.support_autocorrect?

Returns if class supports autocorrect.

.support_multiple_source?

Override if your cop should be called repeatedly for multiple investigations Between calls to on_new_investigation and on_investigation_end, the result of processed_source will remain constant.

Class Method Summary

::RuboCop::Cop::Base - Inherited

.autocorrect_incompatible_with

List of cops that should not try to autocorrect at the same time as this cop.

.badge

Naming.

.callbacks_needed, .cop_name, .department,
.documentation_url

Returns an url to view this cops documentation online.

.exclude_from_registry

Call for abstract Cop classes.

.inherited,
.joining_forces

Override and return the Force class(es) you need to join.

.match?

Returns true if the cop name or the cop namespace matches any of the given names.

.new,
.requires_gem

Register a version requirement for the given gem name.

.restrict_on_send

::RuboCop::ExcludeLimit - Extended

exclude_limit

Sets up a configuration option to have an exclude limit tracked.

transform

Instance Attribute Summary

Instance Method Summary

::RuboCop::Cop::AllowedPattern - Included

::RuboCop::Cop::AllowedMethods - Included

::RuboCop::Cop::RangeHelp - Included

#add_range, #column_offset_between,
#contents_range

A range containing only the contents of a literal with delimiters (e.g.

#directions,
#effective_column

Returns the column attribute of the range, except if the range is on the first line and there’s a byte order mark at the beginning of that line, in which case 1 is subtracted from the column value.

#final_pos, #move_pos, #move_pos_str, #range_between, #range_by_whole_lines, #range_with_comments, #range_with_comments_and_lines, #range_with_surrounding_comma, #range_with_surrounding_space, #source_range

::RuboCop::Cop::Base - Inherited

#add_global_offense

Adds an offense that has no particular location.

#add_offense

Adds an offense on the specified range (or node with an expression) Unless that offense is disabled for this range, a corrector will be yielded to provide the cop the opportunity to autocorrect the offense.

#begin_investigation

Called before any investigation.

#callbacks_needed,
#cop_config

Configuration Helpers.

#cop_name, #excluded_file?,
#external_dependency_checksum

This method should be overridden when a cop’s behavior depends on state that lives outside of these locations:

#inspect
#message

Gets called if no message is specified when calling add_offense or add_global_offense Cops are discouraged to override this; instead pass your message directly.

#name

Alias for Base#cop_name.

#offenses,
#on_investigation_end

Called after all on_…​

#on_new_investigation

Called before all on_…​

#on_other_file

Called instead of all on_…​

#parse

There should be very limited reasons for a Cop to do it’s own parsing.

#parser_engine,
#ready

Called between investigations.

#relevant_file?, #target_rails_version, #target_ruby_version, #annotate, #apply_correction, #attempt_correction,
#callback_argument

Reserved for Cop::Cop.

#complete_investigation

Called to complete an investigation.

#correct, #current_corrector,
#current_offense_locations

Reserved for Commissioner:

#current_offenses, #currently_disabled_lines, #custom_severity, #default_severity, #disable_uncorrectable, #enabled_line?, #file_name_matches_any?, #find_message, #find_severity, #range_for_original, #range_from_node_or_range,
#reset_investigation

Actually private methods.

#use_corrector

::RuboCop::Cop::AutocorrectLogic - Included

::RuboCop::Cop::IgnoredNode - Included

Constructor Details

This class inherits a constructor from RuboCop::Cop::Base

Instance Method Details

#class_comparison_candidate?(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/class_equality_comparison.rb', line 64

def_node_matcher :class_comparison_candidate?, <<~PATTERN
  (send
    {$(send _ :class) (send $(send _ :class) #class_name_method?)}
    {:== :equal? :eql?} $_)
PATTERN

#class_name(class_node, node) (private)

[ GitHub ]

  
# 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) ⇒ Boolean (private)

[ GitHub ]

  
# 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) (private)

[ GitHub ]

  
# 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

#on_send(node)

[ GitHub ]

  
# 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

#require_cbase?(class_node) ⇒ Boolean (private)

[ GitHub ]

  
# 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) (private)

[ GitHub ]

  
# 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) ⇒ Boolean (private)

[ GitHub ]

  
# 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