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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.

Note
 When frozen string literals are enabled, String.new isn’t corrected to an empty string since the former is mutable and the latter would be frozen.

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_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,
#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::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_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, #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 Attribute Details

#frozen_strings? ⇒ Boolean (readonly, private)

[ GitHub ] 

  


# File 'lib/rubocop/cop/style/empty_literal.rb', line 140



def frozen_strings?
  return true if frozen_string_literals_enabled?

  frozen_string_cop_enabled = config.cop_enabled?('Style/FrozenStringLiteralComment')
  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 38



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 47



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 58



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 122



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 93



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 41



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 50



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 66



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 113



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 117



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 83



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 73



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 100



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 44



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