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Class: RuboCop::Cop::Style::CollectionQuerying

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/collection_querying.rb

Overview

Prefer Enumerable predicate methods over expressions with count.

The cop checks calls to count without arguments, or with a block. It doesn’t register offenses for count with a positional argument because its behavior differs from predicate methods (count matches the argument using ==, while any?, none? and one? use ===).

Note
 This cop doesn’t check length and size methods because they would yield false positives. For example, ::String implements length and size, but it doesn’t include Enumerable.

Examples:

# bad
x.count.positive?
x.count > 0
x.count != 0

x.count(&:foo?).positive?
x.count { |item| item.foo? }.positive?

# good
x.any?

x.any?(&:foo?)
x.any? { |item| item.foo? }

# bad
x.count.zero?
x.count == 0

# good
x.none?

# bad
x.count == 1
x.one?

AllCops:ActiveSupportExtensionsEnabled: false (default)

# good
x.count > 1

AllCops:ActiveSupportExtensionsEnabled: true

# bad
x.count > 1

# good
x.many?

Cop Safety Information:

  • The cop is unsafe because receiver might not include Enumerable, or it has nonstandard implementation of count or any replacement methods.

    It’s also unsafe because for collections with falsey values, expressions with count without a block return a different result than methods any?, none? and one?:

    [nil, false].count.positive?
[nil].count == 1
# => true

[nil, false].any?
[nil].one?
# => false

[nil].count == 0
# => false

[nil].none?
# => true

    Autocorrection is unsafe when replacement methods don’t iterate over every element in collection and the given block runs side effects:

    x.count(&:method_with_side_effects).positive?
# calls {method_with_side_effects} on every element

x.any?(&:method_with_side_effects)
# calls {method_with_side_effects} until first element returns a truthy value

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

#count_predicate(node)

[ GitHub ] 

  


# File 'lib/rubocop/cop/style/collection_querying.rb', line 115



def_node_matcher :count_predicate, <<~PATTERN
  (send
    {
      (any_block $(call !nil? :count) _ _)
      $(call !nil? :count (block-pass _)?)
    }
    {
      :positive? |
      :> (int 0) |
      :!= (int 0) |
      :zero? |
      :== (int 0) |
      :== (int 1) |
      :> (int 1)
    })
PATTERN


  








  

    #on_send(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/collection_querying.rb', line 132



def on_send(node)
  return unless (count_node = count_predicate(node))

  replacement_method = replacement_method(node)

  return unless replacement_supported?(replacement_method)

  offense_range = count_node.loc.selector.join(node.source_range.end)
  add_offense(offense_range,
              message: format(MSG, prefer: replacement_method)) do |corrector|
    corrector.replace(count_node.loc.selector, replacement_method)
    corrector.remove(removal_range(node))
  end
end


  








  

    #removal_range(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/collection_querying.rb', line 159



def removal_range(node)
  range = (node.loc.dot || node.loc.selector).join(node.source_range.end)

  range_with_surrounding_space(range, side: :left)
end


  








  

    #replacement_method(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/collection_querying.rb', line 149



def replacement_method(node)
  REPLACEMENTS.fetch([node.method_name, node.first_argument&.value])
end


  








  

    #replacement_supported?(method_name)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/collection_querying.rb', line 153



def replacement_supported?(method_name)
  return true if active_support_extensions_enabled?

  method_name != :many?
end