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Class: RuboCop::Cop::Style::ParallelAssignment

Relationships & Source Files
Namespace Children
Classes:
AssignmentSorter, GenericCorrector, ModifierCorrector, RescueCorrector
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::RescueNode, ::RuboCop::Cop::Base, ::RuboCop::Cop::AutocorrectLogic, ::RuboCop::Cop::IgnoredNode, ::RuboCop::Util, RuboCop::AST::Sexp
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/style/parallel_assignment.rb

Overview

Checks for simple usages of parallel assignment. Parallel assignment is less readable than individual assignments and makes it harder to follow what each variable is being set to.

This will only complain when the number of variables being assigned matched the number of assigning variables.

Examples:

# bad
a, b, c = 1, 2, 3
a, b, c = [1, 2, 3]

# good
one, two = *foo
a, b = foo
a, b = b, a

a = 1
b = 2
c = 3

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

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::RescueNode - Included

#modifier_locations, #rescue_modifier?, #rescued_exceptions

::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

#add_self_to_getters(right_elements) (private)

Converts (send nil :something) nodes to (send (:self) :something). This makes the sorting algorithm work for expressions such as self.a, self.b = b, a.

[ GitHub ] 

  


# File 'lib/rubocop/cop/style/parallel_assignment.rb', line 107



def add_self_to_getters(right_elements)
  right_elements.map do |e|
    implicit_self_getter?(e) { |var| s(:send, s(:self), var) } || e
  end
end


  








  

    #allowed_lhs?(elements)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/parallel_assignment.rb', line 66



def allowed_lhs?(elements)
  # Account for edge cases using one variable with a comma
  # E.g.: `foo, = *bar`
  elements.one? || elements.any?(&:splat_type?)
end


  








  

    #allowed_masign?(lhs_elements, rhs_elements)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/parallel_assignment.rb', line 60



def allowed_masign?(lhs_elements, rhs_elements)
  lhs_elements.size != rhs_elements.size ||
    !find_valid_order(lhs_elements,
                      add_self_to_getters(rhs_elements))
end


  








  

    #allowed_rhs?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


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



def allowed_rhs?(node)
  # Edge case for one constant
  elements = Array(node).compact

  # Account for edge case of `Constant::CONSTANT`
  !node.array_type? || elements.any?(&:splat_type?)
end


  








  

    #assignment_corrector(node, rhs, order)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/parallel_assignment.rb', line 80



def assignment_corrector(node, rhs, order)
  if node.parent&.rescue_type?
    _assignment, modifier = *node.parent
  else
    _assignment, modifier = *rhs.parent
  end

  if modifier_statement?(node.parent)
    ModifierCorrector.new(node, rhs, modifier, config, order)
  elsif rescue_modifier?(modifier)
    RescueCorrector.new(node, rhs, modifier, config, order)
  else
    GenericCorrector.new(node, rhs, modifier, config, order)
  end
end


  








  

    #autocorrect(corrector, node, rhs)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/parallel_assignment.rb', line 53



def autocorrect(corrector, node, rhs)
  order = find_valid_order(node.assignments, Array(rhs).compact)
  correction = assignment_corrector(node, rhs, order)

  corrector.replace(correction.correction_range, correction.correction)
end


  








  

    #find_valid_order(left_elements, right_elements)   (private)
  

  [ GitHub ]


  

  


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



def find_valid_order(left_elements, right_elements)
  # arrange left_elements in an order such that no corresponding right
  # element refers to a left element earlier in the sequence
  assignments = left_elements.zip(right_elements)

  AssignmentSorter.new(assignments).tsort
end


  








  

    #implicit_self_getter?(node)   (private)
  

  [ GitHub ]


  

  


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



def_node_matcher :implicit_self_getter?, '(send nil? $_)'


  








  

    #modifier_statement?(node)  ⇒ Boolean 
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/parallel_assignment.rb', line 190



def modifier_statement?(node)
  return false unless node

  node.basic_conditional? && node.modifier_form?
end


  








  

    #on_masgn(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/parallel_assignment.rb', line 33



def on_masgn(node) # rubocop:disable Metrics/AbcSize
  return if part_of_ignored_node?(node)

  rhs = node.rhs
  rhs = rhs.body if rhs.rescue_type?
  rhs_elements = Array(rhs).compact # edge case for one constant

  return if allowed_lhs?(node.assignments) || allowed_rhs?(rhs) ||
            allowed_masign?(node.assignments, rhs_elements)

  range = node.source_range.begin.join(rhs.source_range.end)

  add_offense(range) do |corrector|
    autocorrect(corrector, node, rhs)
  end
  ignore_node(node)
end