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Class: RuboCop::Cop::Style::SwapValues

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/swap_values.rb

Overview

Enforces the use of shorthand-style swapping of 2 variables.

Examples:

# bad
tmp = x
x = y
y = tmp

# good
x, y = y, x

Cop Safety Information:

  • Autocorrection is unsafe, because the temporary variable used to swap variables will be removed, but may be referred to elsewhere.

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

::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.

.builtin?

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

Cops (other than builtin) are encouraged to implement this.

.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::RangeHelp - Included

#add_range, #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_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, #use_corrector

::RuboCop::Cop::AutocorrectLogic - Included

::RuboCop::Cop::IgnoredNode - Included

Constructor Details

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

Instance Method Details

#allowed_assignment?(node) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/swap_values.rb', line 47

def allowed_assignment?(node)
  node.parent&.mlhs_type? || node.parent&.shorthand_asgn?
end

#correction_range(tmp_assign, y_assign) (private)

[ GitHub ]

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

def correction_range(tmp_assign, y_assign)
  range_by_whole_lines(
    range_between(tmp_assign.source_range.begin_pos, y_assign.source_range.end_pos)
  )
end

#lhs(node) (private)

[ GitHub ]

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

def lhs(node)
  case node.type
  when :casgn
    namespace, name, = *node
    if namespace
      "#{namespace.const_name}::#{name}"
    else
      name.to_s
    end
  else
    node.children[0].to_s
  end
end

#message(x_assign, y_assign) (private)

[ GitHub ]

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

def message(x_assign, y_assign)
  format(
    MSG,
    x_line: x_assign.first_line,
    y_line: y_assign.first_line,
    replacement: replacement(x_assign)
  )
end

#on_asgn(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/swap_values.rb', line 30

def on_asgn(node)
  return if allowed_assignment?(node)

  tmp_assign = node
  x_assign, y_assign = *node.right_siblings.take(2)
  return unless x_assign && y_assign && swapping_values?(tmp_assign, x_assign, y_assign)

  add_offense(node, message: message(x_assign, y_assign)) do |corrector|
    range = correction_range(tmp_assign, y_assign)
    corrector.replace(range, replacement(x_assign))
  end
end

#replacement(x_assign) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/swap_values.rb', line 75

def replacement(x_assign)
  x = lhs(x_assign)
  y = rhs(x_assign)
  "#{x}, #{y} = #{y}, #{x}"
end

#rhs(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/swap_values.rb', line 95

def rhs(node)
  case node.type
  when :casgn
    node.children[2].source
  else
    node.children[1].source
  end
end

#simple_assignment?(node) ⇒ Boolean (private)

[ GitHub ]

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

def simple_assignment?(node)
  return false unless node.respond_to?(:type)

  SIMPLE_ASSIGNMENT_TYPES.include?(node.type)
end

#swapping_values?(tmp_assign, x_assign, y_assign) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/swap_values.rb', line 51

def swapping_values?(tmp_assign, x_assign, y_assign)
  simple_assignment?(tmp_assign) &&
    simple_assignment?(x_assign) &&
    simple_assignment?(y_assign) &&
    lhs(x_assign) == rhs(tmp_assign) &&
    lhs(y_assign) == rhs(x_assign) &&
    rhs(y_assign) == lhs(tmp_assign)
end