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Class: RuboCop::Cop::Style::Sample

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:
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/style/sample.rb

Overview

Identifies usages of shuffle.first, shuffle.last, and shuffle[] and change them to use sample instead.

Examples:

# bad
[1, 2, 3].shuffle.first
[1, 2, 3].shuffle.first(2)
[1, 2, 3].shuffle.last
[2, 1, 3].shuffle.at(0)
[2, 1, 3].shuffle.slice(0)
[1, 2, 3].shuffle[2]
[1, 2, 3].shuffle[0, 2]    # sample(2) will do the same
[1, 2, 3].shuffle[0..2]    # sample(3) will do the same
[1, 2, 3].shuffle(random: Random.new).first

# good
[1, 2, 3].shuffle
[1, 2, 3].sample
[1, 2, 3].sample(3)
[1, 2, 3].shuffle[1, 3]    # sample(3) might return a longer Array
[1, 2, 3].shuffle[1..3]    # sample(3) might return a longer Array
[1, 2, 3].shuffle[foo, bar]
[1, 2, 3].shuffle(random: Random.new)

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

Class Attribute Summary

::RuboCop::Cop::AutoCorrector - Extended

::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 an 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

Instance Method Summary

::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

::RuboCop::Cop::IgnoredNode - Included

Constructor Details

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

Instance Method Details

#correction(shuffle_arg, method, method_args) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/sample.rb', line 122

def correction(shuffle_arg, method, method_args)
  shuffle_arg = extract_source(shuffle_arg)
  sample_arg = sample_arg(method, method_args)
  args = [sample_arg, shuffle_arg].compact.join(', ')
  args.empty? ? 'sample' : "sample(#{args})"
end

#extract_source(args) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/sample.rb', line 138

def extract_source(args)
  args.empty? ? nil : args.first.source
end

#message(shuffle_arg, method, method_args, range) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/sample.rb', line 116

def message(shuffle_arg, method, method_args, range)
  format(MSG,
         correct: correction(shuffle_arg, method, method_args),
         incorrect: range.source)
end

#offensive?(method, method_args) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/sample.rb', line 59

def offensive?(method, method_args)
  case method
  when :first, :last
    true
  when :[], :at, :slice
    sample_size(method_args) != :unknown
  else
    false
  end
end

#on_csend(node)

Alias for #on_send.

[ GitHub ]

  
# File 'lib/rubocop/cop/style/sample.rb', line 55

alias on_csend on_send

#on_send(node) Also known as: #on_csend

[ GitHub ]

  
# File 'lib/rubocop/cop/style/sample.rb', line 41

def on_send(node)
  sample_candidate?(node) do |shuffle_node, shuffle_arg, method, method_args|
    return unless offensive?(method, method_args)

    range = source_range(shuffle_node, node)
    message = message(shuffle_arg, method, method_args, range)

    add_offense(range, message: message) do |corrector|
      corrector.replace(
        source_range(shuffle_node, node), correction(shuffle_arg, method, method_args)
      )
    end
  end
end

#range_size(range_node) (private)

Metrics/PerceivedComplexity

[ GitHub ]

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

def range_size(range_node)
  vals = range_node.to_a
  return :unknown unless vals.all? { |val| val.nil? || val.int_type? }

  low, high = vals.map { |val| val.nil? ? 0 : val.children[0] }
  return :unknown unless low.zero? && high >= 0

  case range_node.type
  when :erange
    (low...high).size
  when :irange
    (low..high).size
  end
end

#sample_arg(method, method_args) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/sample.rb', line 129

def sample_arg(method, method_args)
  case method
  when :first, :last
    extract_source(method_args)
  when :[], :slice
    sample_size(method_args)
  end
end

#sample_candidate?(node)

[ GitHub ]

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

def_node_matcher :sample_candidate?, <<~PATTERN
  (call $(call _ :shuffle $...) ${:#{RESTRICT_ON_SEND.join(' :')}} $...)
PATTERN

#sample_size(method_args) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/sample.rb', line 70

def sample_size(method_args)
  case method_args.size
  when 1
    sample_size_for_one_arg(method_args.first)
  when 2
    sample_size_for_two_args(*method_args)
  end
end

#sample_size_for_one_arg(arg) (private)

[ GitHub ]

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

def sample_size_for_one_arg(arg)
  if arg.range_type?
    range_size(arg)
  elsif arg.int_type?
    [0, -1].include?(arg.to_a.first) ? nil : :unknown
  else
    :unknown
  end
end

#sample_size_for_two_args(first, second) (private)

[ GitHub ]

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

def sample_size_for_two_args(first, second)
  return :unknown unless first.int_type? && first.to_a.first.zero?

  second.int_type? ? second.to_a.first : :unknown
end

#source_range(shuffle_node, node) (private)

Metrics/PerceivedComplexity

[ GitHub ]

  
# File 'lib/rubocop/cop/style/sample.rb', line 112

def source_range(shuffle_node, node)
  shuffle_node.loc.selector.join(node.source_range.end)
end