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Class: RuboCop::Cop::Lint::Void

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

Overview

Checks for operators, variables, literals, lambda, proc and nonmutating methods used in void context.

each blocks are allowed to prevent false positives. For example, the expression inside the each block below. It’s not void, especially when the receiver is an Enumerator:

enumerator = [1, 2, 3].filter
enumerator.each { |item| item >= 2 } #=> [2, 3]
Note
 The last expression in an assignment method definition such as def foo=(arg) is not flagged. Ruby discards it (the method returns its argument), but the method can still be called directly and its return value relied upon, so flagging it would be a false positive for this lint.

Examples:

CheckForMethodsWithNoSideEffects: false (default)

# bad
def some_method
  some_num * 10
  do_something
end

def some_method(some_var)
  some_var
  do_something
end

CheckForMethodsWithNoSideEffects: true

# bad
def some_method(some_array)
  some_array.sort
  do_something(some_array)
end

# good
def some_method
  do_something
  some_num * 10
end

def some_method(some_var)
  do_something
  some_var
end

def some_method(some_array)
  some_array.sort!
  do_something(some_array)
end

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

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, #project_index, #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::RangeHelp - Included

#add_range,
#arguments_range

A range containing the first to the last argument of a method call or method definition.
#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_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, #matches_absolute_include_pattern?, #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, #eol_comment, #eol_comment_would_be_inside_literal?, #heredoc_range, #line_with_eol_comment_too_long?, #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, #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

#all_keys_entirely_literal?(node) ⇒ Boolean (private)

[ GitHub ] 

  


# File 'lib/rubocop/cop/lint/void.rb', line 292



def all_keys_entirely_literal?(node)
  node.each_key.all? { |key| entirely_literal?(key) }
end


  








  

    #all_values_entirely_literal?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 296



def all_values_entirely_literal?(node)
  node.each_value.all? { |value| entirely_literal?(value) }
end


  








  

    #autocorrect_nonmutating_send(corrector, node, suggestion)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 270



def autocorrect_nonmutating_send(corrector, node, suggestion)
  send_node = if node.call_type?
                node
              else
                node.send_node
              end
  corrector.replace(send_node.loc.selector, suggestion)
end


  








  

    #autocorrect_void_expression(corrector, node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 263



def autocorrect_void_expression(corrector, node)
  return if node.parent.type?(:if, :case, :when, :case_match, :in_pattern)
  return if (def_node = node.each_ancestor(:any_def).first) && def_node.assignment_method?

  corrector.remove(range_with_surrounding_space(range: node.source_range, side: :left))
end


  








  

    #autocorrect_void_op(corrector, node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 250



def autocorrect_void_op(corrector, node)
  if node.arguments.empty?
    corrector.replace(node, node.receiver.source)
  else
    corrector.remove(node.loc.dot) if node.loc.dot
    corrector.replace(
      range_with_surrounding_space(range: node.loc.selector, side: :both,
                                   newlines: false),
      "\n"
    )
  end
end


  








  

    #check_begin(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 108



def check_begin(node)
  expressions = *node
  inside_each_block = node.each_ancestor(:any_block).first&.method?(:each)
  expressions.pop if !in_void_context?(node) || inside_each_block || setter_method?(node)
  expressions.each do |expr|
    check_void_op(expr) { inside_each_block }
    check_expression(expr)
  end
end


  








  

    #check_case_expression(case_node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 140



def check_case_expression(case_node)
  case_node.each_when { |when_node| check_expression(when_node.body) if when_node.body }
  check_expression(case_node.else_branch) if case_node.else_branch
end


  








  

    #check_case_match_expression(case_node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 145



def check_case_match_expression(case_node)
  case_node.each_in_pattern do |in_pattern_node|
    check_expression(in_pattern_node.body) if in_pattern_node.body
  end
  check_expression(case_node.else_branch) if case_node.else_branch
end


  








  

    #check_ensure(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 231



def check_ensure(node)
  return unless (body = node.branch)
  # NOTE: the `begin` node case is already handled via `on_begin`
  return if body.begin_type?

  check_expression(body)
end


  








  

    #check_expression(expr)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 118



def check_expression(expr)
  return check_if_expression(expr) if expr.if_type?
  return check_case_expression(expr) if expr.case_type?
  return check_case_match_expression(expr) if expr.case_match_type?

  check_void_expression_nodes(expr)
end


  








  

    #check_if_expression(if_node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 136



def check_if_expression(if_node)
  check_void_expression_nodes(if_node.body) if if_node.body
end


  








  

    #check_literal(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 187



def check_literal(node)
  if !entirely_literal?(node) || node.xstr_type? || node.range_type? || node.nil_type?
    return
  end

  add_offense(node, message: format(LIT_MSG, lit: node.source)) do |corrector|
    autocorrect_void_expression(corrector, node)
  end
end


  








  

    #check_nonmutating(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 213



def check_nonmutating(node)
  return unless node.type?(:call, :any_block)

  method_name = node.method_name
  return unless NONMUTATING_METHODS.include?(method_name)

  suggestion = if METHODS_REPLACEABLE_BY_EACH.include?(method_name)
                 'each'
               else
                 "#{method_name}!"
               end
  add_offense(node,
              message: format(NONMUTATING_MSG, method: method_name,
                                               suggest: suggestion)) do |corrector|
    autocorrect_nonmutating_send(corrector, node, suggestion)
  end
end


  








  

    #check_self(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 197



def check_self(node)
  return unless node.self_type?

  add_offense(node, message: SELF_MSG) do |corrector|
    autocorrect_void_expression(corrector, node)
  end
end


  








  

    #check_var(node)   (private)
  



  

    


Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 169



def check_var(node)
  return unless node.variable? || node.const_type?

  if node.const_type?
    template = node.special_keyword? ? VAR_MSG : CONST_MSG

    offense_range = node
    message = format(template, var: node.source)
  else
    offense_range = node.loc.name
    message = format(VAR_MSG, var: node.loc.name.source)
  end

  add_offense(offense_range, message: message) do |corrector|
    autocorrect_void_expression(corrector, node)
  end
end


  








  

    #check_void_expression(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 205



def check_void_expression(node)
  return unless node.defined_type? || node.lambda_or_proc?

  add_offense(node, message: format(EXPRESSION_MSG, expression: node.source)) do |corrector|
    autocorrect_void_expression(corrector, node)
  end
end


  








  

    #check_void_expression_nodes(expr)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 126



def check_void_expression_nodes(expr)
  check_literal(expr)
  check_var(expr)
  check_self(expr)
  check_void_expression(expr)
  return unless cop_config['CheckForMethodsWithNoSideEffects']

  check_nonmutating(expr)
end


  








  

    #check_void_op(node, &block)   (private)
  



  

    


Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 153



def check_void_op(node, &block)
  node = node.children.first while node&.begin_type?
  return unless node&.call_type? && OPERATORS.include?(node.method_name)
  if !UNARY_OPERATORS.include?(node.method_name) && node.loc.dot && node.arguments.none?
    return
  end

  return if block && yield(node)

  add_offense(node.loc.selector,
              message: format(OP_MSG, op: node.method_name)) do |corrector|
    autocorrect_void_op(corrector, node)
  end
end


  








  

    #entirely_literal?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 279



def entirely_literal?(node)
  case node.type
  when :array
    all_values_entirely_literal?(node)
  when :hash
    all_keys_entirely_literal?(node) && all_values_entirely_literal?(node)
  when :send, :csend
    node.method?(:freeze) && node.receiver && entirely_literal?(node.receiver)
  else
    node.literal?
  end
end


  








  

    #in_void_context?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 239



def in_void_context?(node)
  parent = node.parent
  return false unless parent && parent.children.last == node

  parent.respond_to?(:void_context?) && parent.void_context?
end


  








  

    #on_begin(node)  
    Also known as: #on_kwbegin
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 97



def on_begin(node)
  check_begin(node)
end


  








  

    #on_block(node)  
    Also known as: #on_numblock, #on_itblock
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 86



def on_block(node)
  return unless node.body && !node.body.begin_type?
  return unless in_void_context?(node.body)
  return if node.method?(:each)

  check_void_op(node.body)
  check_expression(node.body)
end


  








  

    #on_ensure(node)  
  

  [ GitHub ]


  

  


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



def on_ensure(node)
  check_ensure(node)
end


  








  

    #on_itblock(node)  
  



  

    


Alias for #on_block.



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 95



alias on_itblock on_block


  








  

    #on_kwbegin(node)  
  



  

    


Alias for #on_begin.



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 100



alias on_kwbegin on_begin


  








  

    #on_numblock(node)  
  



  

    


Alias for #on_block.



  



  [ GitHub ]


  

  


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



alias on_numblock on_block


  








  

    #setter_method?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/lint/void.rb', line 246



def setter_method?(node)
  node.parent&.any_def_type? && node.parent.assignment_method?
end