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Class: RuboCop::Cop::Style::EmptyLiteral

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::StringLiteralsHelp, ::RuboCop::Cop::RangeHelp, ::RuboCop::Cop::FrozenStringLiteral, ::RuboCop::Cop::Base, ::RuboCop::Cop::AutocorrectLogic, ::RuboCop::Cop::IgnoredNode, ::RuboCop::Util, RuboCop::AST::Sexp
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/style/empty_literal.rb

Overview

Checks for the use of a method, the result of which would be a literal, like an empty array, hash, or string.

Examples:

# bad
a = Array.new
a = Array[]
h = Hash.new
h = Hash[]
s = String.new

# good
a = []
h = {}
s = ''

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

::RuboCop::Cop::FrozenStringLiteral - Included

FROZEN_STRING_LITERAL, FROZEN_STRING_LITERAL_ENABLED, FROZEN_STRING_LITERAL_TYPES_RUBY27

::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::StringLiteralsHelp - Included

#enforce_double_quotes?

::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::StringLiteralsHelp - Included

#preferred_string_literal, #string_literals_config, #wrong_quotes?

::RuboCop::Cop::RangeHelp - Included

#add_range, #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::FrozenStringLiteral - Included

#frozen_heredoc?, #frozen_string_literal?, #frozen_string_literal_comment_exists?, #frozen_string_literal_specified?, #frozen_string_literals_disabled?, #frozen_string_literals_enabled?, #leading_comment_lines, #leading_magic_comments, #uninterpolated_heredoc?, #uninterpolated_string?

::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

Instance Attribute Details

#frozen_strings? ⇒ Boolean (readonly, private)

[ GitHub ] 

  


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



def frozen_strings?
  return true if frozen_string_literals_enabled?

  frozen_string_cop_enabled = config.for_cop('Style/FrozenStringLiteralComment')['Enabled']
  frozen_string_cop_enabled &&
    !frozen_string_literals_disabled? &&
    string_literals_frozen_by_default?.nil?
end


  







Instance Method Details



  

    #array_node(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 34



def_node_matcher :array_node, '(send (const {nil? cbase} :Array) :new (array)?)'


  








  

    #array_with_block(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 43



def_node_matcher :array_with_block, '(block (send (const {nil? cbase} :Array) :new) args _)'


  








  

    #array_with_index(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 54



def_node_matcher :array_with_index, <<~PATTERN
  {
    (send (const {nil? cbase} :Array) :[])
    (send nil? :Array (array))
  }
PATTERN


  








  

    #correction(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 118



def correction(node)
  if offense_array_node?(node)
    '[]'
  elsif str_node(node)
    preferred_string_literal
  elsif offense_hash_node?(node)
    if first_argument_unparenthesized?(node)
      # `some_method {}` is not same as `some_method Hash.new`
      # because the braces are interpreted as a block. We will have
      # to rewrite the arguments to wrap them in parenthesis.
      args = node.parent.arguments
      "(#{args[1..].map(&:source).unshift('{}').join(', ')})"
    else
      '{}'
    end
  end
end


  








  

    #first_argument_unparenthesized?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 89



def first_argument_unparenthesized?(node)
  parent = node.parent
  return false unless parent && %i[send super zsuper].include?(parent.type)

  node.equal?(parent.first_argument) && !parentheses?(node.parent)
end


  








  

    #hash_node(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 37



def_node_matcher :hash_node, '(send (const {nil? cbase} :Hash) :new)'


  








  

    #hash_with_block(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 46



def_node_matcher :hash_with_block, <<~PATTERN
  {
    (block (send (const {nil? cbase} :Hash) :new) args _)
    (numblock (send (const {nil? cbase} :Hash) :new) ...)
  }
PATTERN


  








  

    #hash_with_index(node)  
  

  [ GitHub ]


  

  


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



def_node_matcher :hash_with_index, <<~PATTERN
  {
    (send (const {nil? cbase} :Hash) :[])
    (send nil? :Hash (array))
  }
PATTERN


  








  

    #offense_array_node?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 109



def offense_array_node?(node)
  (array_node(node) && !array_with_block(node.parent)) || array_with_index(node)
end


  








  

    #offense_hash_node?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 113



def offense_hash_node?(node)
  # If Hash.new takes a block, it can't be changed to {}.
  (hash_node(node) && !hash_with_block(node.parent)) || hash_with_index(node)
end


  








  

    #offense_message(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 79



def offense_message(node)
  if offense_array_node?(node)
    format(ARR_MSG, current: node.source)
  elsif offense_hash_node?(node)
    format(HASH_MSG, current: node.source)
  elsif str_node(node) && !frozen_strings?
    format(STR_MSG, prefer: preferred_string_literal)
  end
end


  








  

    #on_send(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 69



def on_send(node)
  return unless (message = offense_message(node))

  add_offense(node, message: message) do |corrector|
    corrector.replace(replacement_range(node), correction(node))
  end
end


  








  

    #replacement_range(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 96



def replacement_range(node)
  if hash_node(node) && first_argument_unparenthesized?(node)
    # `some_method {}` is not same as `some_method Hash.new`
    # because the braces are interpreted as a block. We will have
    # to rewrite the arguments to wrap them in parenthesis.
    args = node.parent.arguments

    range_between(args[0].source_range.begin_pos - 1, args[-1].source_range.end_pos)
  else
    node.source_range
  end
end


  








  

    #str_node(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 40



def_node_matcher :str_node, '(send (const {nil? cbase} :String) :new)'