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Class: RuboCop::Cop::Lint::UnusedMethodArgument

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

Overview

Checks for unused method arguments.

Examples:

# bad
def some_method(used, unused, _unused_but_allowed)
  puts used
end

# good
def some_method(used, _unused, _unused_but_allowed)
  puts used
end

AllowUnusedKeywordArguments: false (default)

# bad
def do_something(used, unused: 42)
  used
end

AllowUnusedKeywordArguments: true

# good
def do_something(used, unused: 42)
  used
end

IgnoreEmptyMethods: true (default)

# good
def do_something(unused)
end

IgnoreEmptyMethods: false

# bad
def do_something(unused)
end

IgnoreNotImplementedMethods: true (default)

# with default value of `NotImplementedExceptions: ['NotImplementedError']`

# good
def do_something(unused)
  raise NotImplementedError
end

def do_something_else(unused)
  fail "TODO"
end

IgnoreNotImplementedMethods: true

# with `NotImplementedExceptions: ['AbstractMethodError']`

# good
def do_something(unused)
  raise AbstractMethodError
end

IgnoreNotImplementedMethods: false

# bad
def do_something(unused)
  raise NotImplementedError
end

def do_something_else(unused)
  fail "TODO"
end

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

UnusedArgument - Included

#after_leaving_scope, #check_argument

::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

#disable_offense, #disable_offense_at_end_of_line, #disable_offense_before_and_after, #disable_offense_with_eol_or_surround_comment, #max_line_length,
#range_by_lines

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

Class Method Details

.autocorrect_incompatible_with

[ GitHub ] 

  


# File 'lib/rubocop/cop/lint/unused_method_argument.rb', line 80



def self.autocorrect_incompatible_with
  [Style::ExplicitBlockArgument]
end


  








  

    .joining_forces  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_method_argument.rb', line 84



def self.joining_forces
  VariableForce
end


  







Instance Method Details



  

    #allowed_exception_class?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_method_argument.rb', line 128



def allowed_exception_class?(node)
  return false unless node.const_type?

  allowed_class_names = Array(cop_config.fetch('NotImplementedExceptions', []))
  allowed_class_names.include?(node.const_name)
end


  








  

    #autocorrect(corrector, node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_method_argument.rb', line 90



def autocorrect(corrector, node)
  UnusedArgCorrector.correct(corrector, processed_source, node)
end


  








  

    #check_argument(variable)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_method_argument.rb', line 94



def check_argument(variable)
  return unless variable.method_argument?
  return if variable.keyword_argument? && cop_config['AllowUnusedKeywordArguments']
  return if ignored_method?(variable.scope.node.body)

  super
end


  








  

    #ignored_method?(body)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_method_argument.rb', line 102



def ignored_method?(body)
  (cop_config['IgnoreEmptyMethods'] && body.nil?) ||
    (cop_config['IgnoreNotImplementedMethods'] && not_implemented?(body))
end


  








  

    #message(variable)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_method_argument.rb', line 107



def message(variable)
  message = +"Unused method argument - `#{variable.name}`."

  unless variable.keyword_argument?
    message << " If it's necessary, use `_` or `_#{variable.name}` " \
               "as an argument name to indicate that it won't be used. " \
               "If it's unnecessary, remove it."
  end

  scope = variable.scope
  all_arguments = scope.variables.each_value.select(&:method_argument?)

  if all_arguments.none?(&:referenced?)
    message << " You can also write as `#{scope.name}(*)` " \
               'if you want the method to accept any arguments ' \
               "but don't care about them."
  end

  message
end


  








  

    #not_implemented?(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_method_argument.rb', line 75



def_node_matcher :not_implemented?, <<~PATTERN
  {(send nil? :raise #allowed_exception_class? ...)
   (send nil? :fail ...)}
PATTERN