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Class: RuboCop::Cop::Style::MultipleComparison

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/multiple_comparison.rb

Overview

Checks against comparing a variable with multiple items, where Array#include?, Set#include? or a case could be used instead to avoid code repetition. It accepts comparisons of multiple method calls to avoid unnecessary method calls by default. It can be configured by AllowMethodComparison option.

Examples:

# bad
a = 'a'
foo if a == 'a' || a == 'b' || a == 'c'

# good
a = 'a'
foo if ['a', 'b', 'c'].include?(a)

VALUES = Set['a', 'b', 'c'].freeze
# elsewhere...
foo if VALUES.include?(a)

case foo
when 'a', 'b', 'c' then foo
# ...
end

# accepted (but consider `case` as above)
foo if a == b.lightweight || a == b.heavyweight

AllowMethodComparison: true (default)

# good
foo if a == b.lightweight || a == b.heavyweight

AllowMethodComparison: false

# bad
foo if a == b.lightweight || a == b.heavyweight

# good
foo if [b.lightweight, b.heavyweight].include?(a)

ComparisonsThreshold: 2 (default)

# bad
foo if a == 'a' || a == 'b'

ComparisonsThreshold: 3

# good
foo if a == 'a' || a == 'b'

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

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::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 Attribute Details

#allow_method_comparison?Boolean (readonly, private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 161

def allow_method_comparison?
  cop_config.fetch('AllowMethodComparison', true)
end

Instance Method Details

#comparison?(node) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 136

def comparison?(node)
  simple_comparison_lhs?(node) || simple_comparison_rhs?(node) || nested_comparison?(node)
end

#comparisons_threshold (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 165

def comparisons_threshold
  cop_config.fetch('ComparisonsThreshold', 2)
end

#nested_comparison?(node) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 128

def nested_comparison?(node)
  if node.or_type?
    node.node_parts.all? { |node_part| comparison? node_part }
  else
    false
  end
end

#nested_variable_comparison?(node) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 97

def nested_variable_comparison?(node)
  return false unless nested_comparison?(node)

  variables_in_node(node).count == 1
end

#on_new_investigation

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 58

def on_new_investigation
  @last_comparison = nil
end

#on_or(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 62

def on_or(node)
  reset_comparison if switch_comparison?(node)

  root_of_or_node = root_of_or_node(node)

  return unless node == root_of_or_node
  return unless nested_variable_comparison?(root_of_or_node)
  return if @allowed_method_comparison
  return if @compared_elements.size < comparisons_threshold

  add_offense(node) do |corrector|
    elements = @compared_elements.join(', ')
    prefer_method = "[#{elements}].include?(#{variables_in_node(node).first})"

    corrector.replace(node, prefer_method)
  end

  @last_comparison = node
end

#reset_comparison (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 156

def reset_comparison
  @compared_elements = []
  @allowed_method_comparison = false
end

#root_of_or_node(or_node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 140

def root_of_or_node(or_node)
  return or_node unless or_node.parent

  if or_node.parent.or_type?
    root_of_or_node(or_node.parent)
  else
    or_node
  end
end

#simple_comparison_lhs?(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 88

def_node_matcher :simple_comparison_lhs?, <<~PATTERN
  (send $lvar :== $_)
PATTERN

#simple_comparison_rhs?(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 93

def_node_matcher :simple_comparison_rhs?, <<~PATTERN
  (send $_ :== $lvar)
PATTERN

#simple_double_comparison?(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 85

def_node_matcher :simple_double_comparison?, '(send $lvar :== $lvar)'

#switch_comparison?(node) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 150

def switch_comparison?(node)
  return true if @last_comparison.nil?

  @last_comparison.descendants.none?(node)
end

#variable_name(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 124

def variable_name(node)
  node.children[0]
end

#variables_in_node(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 103

def variables_in_node(node)
  if node.or_type?
    node.node_parts.flat_map { |node_part| variables_in_node(node_part) }.uniq
  else
    variables_in_simple_node(node)
  end
end

#variables_in_simple_node(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/multiple_comparison.rb', line 111

def variables_in_simple_node(node)
  simple_double_comparison?(node) do |var1, var2|
    return [variable_name(var1), variable_name(var2)]
  end
  if (var, obj = simple_comparison_lhs?(node)) || (obj, var = simple_comparison_rhs?(node))
    @allowed_method_comparison = true if allow_method_comparison? && obj.send_type?
    @compared_elements << obj.source
    return [variable_name(var)]
  end

  []
end