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Class: RuboCop::Cop::Lint::NumericOperationWithConstantResult

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:
self, ::RuboCop::Cop::Base, ::RuboCop::Cop::AutocorrectLogic, ::RuboCop::Cop::IgnoredNode, ::RuboCop::Util, RuboCop::AST::Sexp
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb

Overview

Certain numeric operations have a constant result, usually 0 or 1. Multiplying a number by 0 will always return 0. Dividing a number by itself or raising it to the power of 0 will always return 1. As such, they can be replaced with that result. These are probably leftover from debugging, or are mistakes. Other numeric operations that are similarly leftover from debugging or mistakes are handled by Lint/UselessNumericOperation.

Note
 This cop doesn’t detect offenses for the - and % operator because it can’t determine the type of x. If x is an Array or String, it doesn’t perform a numeric operation.

Examples:

# bad
x * 0

# good
0

# bad
x *= 0

# good
x = 0

# bad
x / x
x ** 0

# good
1

# bad
x /= x
x **= 0

# good
x = 1

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

Class Attribute Summary

::RuboCop::Cop::AutoCorrector - Extended

support_autocorrect?

::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 a 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

::RuboCop::Cop::Base - Inherited

#active_support_extensions_enabled?, #always_autocorrect?, #config, #config_to_allow_offenses, #config_to_allow_offenses=, #contextual_autocorrect?, #processed_source, #string_literals_frozen_by_default?, #target_satisfies_all_gem_version_requirements?

::RuboCop::Cop::AutocorrectLogic - Included

#autocorrect?, #autocorrect_enabled?, #autocorrect_requested?, #autocorrect_with_disable_uncorrectable?, #correctable?, #disable_uncorrectable?, #safe_autocorrect?

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_gem_version

Returns a gems locked versions (i.e.
#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

#disable_offense, #disable_offense_at_end_of_line, #disable_offense_before_and_after, #disable_offense_with_eol_or_surround_comment, #heredoc_range, #max_line_length, #multiline_ranges, #multiline_string?,
#range_by_lines

Expand the given range to include all of any lines it covers.
#range_of_first_line, #range_overlaps_offense?, #string_continuation?, #surrounding_heredoc?, #surrounding_percent_array?

::RuboCop::Cop::IgnoredNode - Included

#ignore_node, #ignored_node?, #part_of_ignored_node?, #ignored_nodes

Constructor Details

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

Instance Method Details

#abbreviated_assignment_with_constant_result?(node)

[ GitHub ] 

  


# File 'lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb', line 56



def_node_matcher :abbreviated_assignment_with_constant_result?,
                 '(op-asgn (lvasgn $_) $_ ({int | lvar} $_))'


  








  

    #constant_result?(variable, operation, number)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb', line 85



def constant_result?(variable, operation, number)
  if number.to_s == '0'
    return 0 if operation == :*
    return 1 if operation == :**
  elsif number == variable
    return 1 if operation == :/
  end
  # If we weren't able to find any matches, return false so we can bail out.
  false
end


  








  

    #on_op_asgn(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb', line 71



def on_op_asgn(node)
  return unless abbreviated_assignment_with_constant_result?(node)

  variable, operation, number = abbreviated_assignment_with_constant_result?(node)
  result = constant_result?(variable, operation, number)
  return unless result

  add_offense(node) do |corrector|
    corrector.replace(node, "#{variable} = #{result}")
  end
end


  








  

    #on_send(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb', line 59



def on_send(node)
  return unless operation_with_constant_result?(node)

  variable, operation, number = operation_with_constant_result?(node)
  result = constant_result?(variable, operation, number)
  return unless result

  add_offense(node) do |corrector|
    corrector.replace(node, result.to_s)
  end
end


  








  

    #operation_with_constant_result?(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb', line 52



def_node_matcher :operation_with_constant_result?,
                 '(send (send nil? $_) $_ ({int | send nil?} $_))'