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Class: RuboCop::Cop::Style::SelectByKind

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/style/select_by_kind.rb

Overview

Looks for places where a subset of an Enumerable (array, range, set, etc.; see note below) is calculated based on a class type check, and suggests grep or grep_v instead.

Note
 Hashes do not behave as you may expect with grep, which means that hash.grep is not equivalent to hash.select. Although RuboCop is limited by static analysis, this cop attempts to avoid registering an offense when the receiver is a hash (hash literal, Hash.new, Hash#[], or to_h/to_hash).

Examples:

# bad (select or find_all)
array.select { |x| x.is_a?(Foo) }
array.select { |x| x.kind_of?(Foo) }

# bad (reject)
array.reject { |x| x.is_a?(Foo) }

# bad (negative form)
array.reject { |x| !x.is_a?(Foo) }

# good
array.grep(Foo)
array.grep_v(Foo)

Cop Safety Information:

  • Autocorrection is marked as unsafe because the cop cannot guarantee that the receiver is actually an array by static analysis, so the correction may not be actually equivalent.

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, #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, #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

#calls_lvar?(node, name)

[ GitHub ] 

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 72



def_node_matcher :calls_lvar?, <<~PATTERN
  (send (lvar %1) %CLASS_CHECK_METHODS _)
PATTERN


  








  

    #class_check?(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 45



def_node_matcher :class_check?, <<~PATTERN
  {
    (block call (args (arg $_)) ${(send (lvar _) %CLASS_CHECK_METHODS _)})
    (block call (args (arg $_)) ${(send (send (lvar _) %CLASS_CHECK_METHODS _) :!)})
    (numblock call $1 ${(send (lvar _) %CLASS_CHECK_METHODS _)})
    (numblock call $1 ${(send (send (lvar _) %CLASS_CHECK_METHODS _) :!)})
    (itblock call $_ ${(send (lvar _) %CLASS_CHECK_METHODS _)})
    (itblock call $_ ${(send (send (lvar _) %CLASS_CHECK_METHODS _) :!)})
  }
PATTERN


  








  

    #creates_hash?(node)  
  



  

    


Returns true if a node appears to return a hash



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 58



def_node_matcher :creates_hash?, <<~PATTERN
  {
    (call (const _ :Hash) {:new :[]} ...)
    (block (call (const _ :Hash) :new ...) ...)
    (call _ { :to_h :to_hash } ...)
  }
PATTERN


  








  

    #env_const?(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 67



def_node_matcher :env_const?, <<~PATTERN
  (const {nil? cbase} :ENV)
PATTERN


  








  

    #extract_send_node(block_node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 125



def extract_send_node(block_node)
  return unless (block_arg_name, class_check_send_node = class_check?(block_node))

  block_arg_name = :"_#{block_arg_name}" if block_node.numblock_type?
  block_arg_name = :it if block_node.type?(:itblock)

  inner_node = unwrap_negation(class_check_send_node)

  if calls_lvar?(inner_node, block_arg_name) ||
     negated_calls_lvar?(class_check_send_node, block_arg_name)
    class_check_send_node
  end
end


  








  

    #find_class_constant(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 151



def find_class_constant(node)
  inner_node = unwrap_negation(node)
  inner_node.first_argument if inner_node.send_type?
end


  








  

    #negated?(class_check_send_node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 139



def negated?(class_check_send_node)
  class_check_send_node.send_type? && class_check_send_node.method?(:!)
end


  








  

    #negated_calls_lvar?(node, name)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 77



def_node_matcher :negated_calls_lvar?, <<~PATTERN
  (send (send (lvar %1) %CLASS_CHECK_METHODS _) :!)
PATTERN


  








  

    #on_csend(node)  
  



  

    


Alias for #on_send.



  



  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 92



alias on_csend on_send


  








  

    #on_send(node)  
    Also known as: #on_csend
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 81



def on_send(node)
  return unless (block_node = node.block_node)
  return if block_node.body&.begin_type?
  return if receiver_allowed?(block_node.receiver)
  return unless (class_check_send_node = extract_send_node(block_node))

  replacement = replacement(class_check_send_node, node)
  class_constant = find_class_constant(class_check_send_node)

  register_offense(node, block_node, class_constant, replacement)
end


  








  

    #receiver_allowed?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


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



def receiver_allowed?(node)
  return false unless node

  node.hash_type? || creates_hash?(node) || env_const?(node)
end


  








  

    #register_offense(node, block_node, class_constant, replacement)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 114



def register_offense(node, block_node, class_constant, replacement)
  message = format(MSG, replacement: replacement, original_method: node.method_name)

  add_offense(block_node, message: message) do |corrector|
    if class_constant
      range = range_between(node.loc.selector.begin_pos, block_node.loc.end.end_pos)
      corrector.replace(range, "#{replacement}(#{class_constant.source})")
    end
  end
end


  








  

    #replacement(class_check_send_node, node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 102



def replacement(class_check_send_node, node)
  negated = negated?(class_check_send_node)

  method_name = node.method_name

  if SELECT_METHODS.include?(method_name)
    negated ? 'grep_v' : 'grep'
  else # reject
    negated ? 'grep' : 'grep_v'
  end
end


  








  

    #unwrap_negation(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/select_by_kind.rb', line 143



def unwrap_negation(node)
  if node.send_type? && node.method?(:!)
    node.receiver
  else
    node
  end
end