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Class: RuboCop::Cop::Lint::UnusedBlockArgument

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_block_argument.rb

Overview

Checks for unused block arguments.

Examples:

# bad
do_something do |used, unused|
  puts used
end

do_something do |bar|
  puts :foo
end

define_method(:foo) do |bar|
  puts :baz
end

# good
do_something do |used, _unused|
  puts used
end

do_something do
  puts :foo
end

define_method(:foo) do |_bar|
  puts :baz
end

IgnoreEmptyBlocks: true (default)

# good
do_something { |unused| }

IgnoreEmptyBlocks: false

# bad
do_something { |unused| }

AllowUnusedKeywordArguments: false (default)

# bad
do_something do |unused: 42|
  foo
end

AllowUnusedKeywordArguments: true

# good
do_something do |unused: 42|
  foo
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_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

Class Method Details

.joining_forces

[ GitHub ] 

  


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



def self.joining_forces
  VariableForce
end


  







Instance Attribute Details



  

    #allow_unused_keyword_arguments?  ⇒ Boolean  (readonly, private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 162



def allow_unused_keyword_arguments?
  cop_config['AllowUnusedKeywordArguments']
end


  








  

    #ignore_empty_blocks?  ⇒ Boolean  (readonly, private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 166



def ignore_empty_blocks?
  cop_config['IgnoreEmptyBlocks']
end


  







Instance Method Details



  

    #allowed_block?(variable)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 81



def allowed_block?(variable)
  !variable.block_argument? || (ignore_empty_blocks? && empty_block?(variable))
end


  








  

    #allowed_keyword_argument?(variable)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


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



def allowed_keyword_argument?(variable)
  variable.keyword_argument? && allow_unused_keyword_arguments?
end


  








  

    #augment_message(message, variable)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 99



def augment_message(message, variable)
  scope = variable.scope
  all_arguments = scope.variables.each_value.select(&:block_argument?)

  augmentation = if scope.node.lambda?
                   message_for_lambda(variable, all_arguments)
                 else
                   message_for_normal_block(variable, all_arguments)
                 end

  [message, augmentation].join(' ')
end


  








  

    #autocorrect(corrector, node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 65



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


  








  

    #check_argument(variable)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 69



def check_argument(variable)
  return if allowed_block?(variable) ||
            allowed_keyword_argument?(variable) ||
            used_block_local?(variable)

  super
end


  








  

    #define_method_call?(variable)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 149



def define_method_call?(variable)
  call, = *variable.scope.node
  _, method, = *call

  method == :define_method
end


  








  

    #empty_block?(variable)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 156



def empty_block?(variable)
  _send, _args, body = *variable.scope.node

  body.nil?
end


  








  

    #message(variable)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 89



def message(variable)
  message = "Unused #{variable_type(variable)} - `#{variable.name}`."

  if variable.explicit_block_local_variable?
    message
  else
    augment_message(message, variable)
  end
end


  








  

    #message_for_lambda(variable, all_arguments)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 132



def message_for_lambda(variable, all_arguments)
  message = message_for_underscore_prefix(variable)

  if all_arguments.none?(&:referenced?)
    proc_message = 'Also consider using a proc without arguments ' \
                   'instead of a lambda if you want it ' \
                   "to accept any arguments but don't care about them."
  end

  [message, proc_message].compact.join(' ')
end


  








  

    #message_for_normal_block(variable, all_arguments)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 120



def message_for_normal_block(variable, all_arguments)
  if all_arguments.none?(&:referenced?) && !define_method_call?(variable)
    if all_arguments.count > 1
      "You can omit all the arguments if you don't care about them."
    else
      "You can omit the argument if you don't care about it."
    end
  else
    message_for_underscore_prefix(variable)
  end
end


  








  

    #message_for_underscore_prefix(variable)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 144



def message_for_underscore_prefix(variable)
  "If it's necessary, use `_` or `_#{variable.name}` " \
    "as an argument name to indicate that it won't be used."
end


  








  

    #used_block_local?(variable)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 77



def used_block_local?(variable)
  variable.explicit_block_local_variable? && !variable.assignments.empty?
end


  








  

    #variable_type(variable)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/unused_block_argument.rb', line 112



def variable_type(variable)
  if variable.explicit_block_local_variable?
    'block local variable'
  else
    'block argument'
  end
end