Class: RuboCop::Cop::Style::RedundantSort

Inherits:
Base
  • Object
show all
Extended by:
AutoCorrector
Includes:
RangeHelp
Defined in:
lib/rubocop/cop/style/redundant_sort.rb

Overview

Identifies instances of sorting and then taking only the first or last element. The same behavior can be accomplished without a relatively expensive sort by using Enumerable#min instead of sorting and taking the first element and Enumerable#max instead of sorting and taking the last element. Similarly, Enumerable#min_by and Enumerable#max_by can replace Enumerable#sort_by calls after which only the first or last element is used.

Examples:

# bad
[2, 1, 3].sort.first
[2, 1, 3].sort[0]
[2, 1, 3].sort.at(0)
[2, 1, 3].sort.slice(0)

# good
[2, 1, 3].min

# bad
[2, 1, 3].sort.last
[2, 1, 3].sort[-1]
[2, 1, 3].sort.at(-1)
[2, 1, 3].sort.slice(-1)

# good
[2, 1, 3].max

# bad
arr.sort_by(&:foo).first
arr.sort_by(&:foo)[0]
arr.sort_by(&:foo).at(0)
arr.sort_by(&:foo).slice(0)

# good
arr.min_by(&:foo)

# bad
arr.sort_by(&:foo).last
arr.sort_by(&:foo)[-1]
arr.sort_by(&:foo).at(-1)
arr.sort_by(&:foo).slice(-1)

# good
arr.max_by(&:foo)

Cop Safety Information:

  • This cop is unsafe, because sort…​last and max may not return the same element in all cases.

    In an enumerable where there are multiple elements where a <⇒ b == 0, or where the transformation done by the sort_by block has the same result, sort.last and max (or sort_by.last and max_by) will return different elements. sort.last will return the last element but max will return the first element.

    For example:

      class MyString < String; end
  strings = [MyString.new('test'), 'test']
  strings.sort.last.class   #=> String
  strings.max.class         #=> MyString
      words = %w(dog horse mouse)
  words.sort_by { |word| word.length }.last   #=> 'mouse'
  words.max_by { |word| word.length }         #=> 'horse'

Constant Summary collapse

MSG = 
'Use `%<suggestion>s` instead of `%<sorter>s...%<accessor_source>s`.'
RESTRICT_ON_SEND = 
%i[sort sort_by].freeze

Instance Attribute Summary

Attributes inherited from Base

#config, #processed_source

Instance Method Summary collapse

Methods included from AutoCorrector

support_autocorrect?

Methods inherited from Base

#active_support_extensions_enabled?, #add_global_offense, #add_offense, autocorrect_incompatible_with, badge, #begin_investigation, callbacks_needed, #callbacks_needed, #config_to_allow_offenses, #config_to_allow_offenses=, #cop_config, cop_name, #cop_name, department, documentation_url, exclude_from_registry, #excluded_file?, #external_dependency_checksum, inherited, #initialize, #inspect, joining_forces, lint?, match?, #offenses, #on_investigation_end, #on_new_investigation, #on_other_file, #parse, #ready, #relevant_file?, support_autocorrect?, support_multiple_source?, #target_rails_version, #target_ruby_version

Methods included from ExcludeLimit

#exclude_limit

Methods included from AutocorrectLogic

#autocorrect?, #autocorrect_enabled?, #autocorrect_requested?, #autocorrect_with_disable_uncorrectable?, #correctable?, #disable_uncorrectable?, #safe_autocorrect?

Methods included from IgnoredNode

#ignore_node, #ignored_node?, #part_of_ignored_node?

Methods included from Util

silence_warnings

Constructor Details

This class inherits a constructor from RuboCop::Cop::Base

Instance Method Details

#on_send(node) ⇒ Object 



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# File 'lib/rubocop/cop/style/redundant_sort.rb', line 104

def on_send(node)
  ancestor, sort_node, sorter, accessor =
    find_redundant_sort(node.parent, node.parent&.parent)
  return unless ancestor

  register_offense(ancestor, sort_node, sorter, accessor)
end

#redundant_sort?(node) ⇒ Object 



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# File 'lib/rubocop/cop/style/redundant_sort.rb', line 88

def_node_matcher :redundant_sort?, <<~MATCHER
  {
    (send $(send _ $:sort) ${:last :first})
    (send $(send _ $:sort) ${:[] :at :slice} {(int 0) (int -1)})

    (send $(send _ $:sort_by _) ${:last :first})
    (send $(send _ $:sort_by _) ${:[] :at :slice} {(int 0) (int -1)})

    (send ({block numblock} $(send _ ${:sort_by :sort}) ...) ${:last :first})
    (send
      ({block numblock} $(send _ ${:sort_by :sort}) ...)
      ${:[] :at :slice} {(int 0) (int -1)}
    )
  }
MATCHER