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Class: RuboCop::Cop::Style::TrailingUnderscoreVariable

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/trailing_underscore_variable.rb

Overview

Checks for extra underscores in variable assignment.

Examples:

# bad
a, b, _ = foo()
a, b, _, = foo()
a, _, _ = foo()
a, _, _, = foo()

# good
a, b, = foo()
a, = foo()
*a, b, _ = foo()
# => We need to know to not include 2 variables in a
a, *b, _ = foo()
# => The correction `a, *b, = foo()` is a syntax error

AllowNamedUnderscoreVariables: true (default)

# good
a, b, _something = foo()

AllowNamedUnderscoreVariables: false

# bad
a, b, _something = foo()

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

::RuboCop::Cop::RangeHelp - Included

BYTE_ORDER_MARK, NOT_GIVEN

::RuboCop::Cop::SurroundingSpace - Included

NO_SPACE_COMMAND, SINGLE_SPACE_REGEXP, SPACE_COMMAND

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::SurroundingSpace - Included

::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

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

#allow_named_underscore_variables (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_underscore_variable.rb', line 92

def allow_named_underscore_variables
  @allow_named_underscore_variables ||= cop_config['AllowNamedUnderscoreVariables']
end

#children_offenses(variables) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_underscore_variable.rb', line 125

def children_offenses(variables)
  variables.select(&:mlhs_type?).flat_map { |v| unneeded_ranges(v) }
end

#find_first_offense(variables) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_underscore_variable.rb', line 57

def find_first_offense(variables)
  first_offense = find_first_possible_offense(variables.reverse)

  return unless first_offense
  return if splat_variable_before?(first_offense, variables)

  first_offense
end

#find_first_possible_offense(variables) (private)

[ GitHub ]

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

def find_first_possible_offense(variables)
  variables.reduce(nil) do |offense, variable|
    break offense unless DISALLOW.include?(variable.type)

    var, = *variable
    var, = *var

    break offense if (allow_named_underscore_variables && var != :_) ||
                     !var.to_s.start_with?(UNDERSCORE)

    variable
  end
end

#main_node_offense(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_underscore_variable.rb', line 108

def main_node_offense(node)
  node.masgn_type? ? (mlhs_node, right = *node) : mlhs_node = node

  variables = *mlhs_node
  first_offense = find_first_offense(variables)

  return unless first_offense

  if unused_variables_only?(first_offense, variables)
    return unused_range(node.type, mlhs_node, right)
  end

  return range_for_parentheses(first_offense, mlhs_node) if Util.parentheses?(mlhs_node)

  range_between(first_offense.source_range.begin_pos, node.loc.operator.begin_pos)
end

#on_masgn(node)

[ GitHub ]

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

def on_masgn(node)
  ranges = unneeded_ranges(node)

  ranges.each do |range|
    good_code = node.source
    offset = range.begin_pos - node.source_range.begin_pos
    good_code[offset, range.size] = ''

    add_offense(range, message: format(MSG, code: good_code)) do |corrector|
      corrector.remove(range)
    end
  end
end

#range_for_parentheses(offense, left) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_underscore_variable.rb', line 146

def range_for_parentheses(offense, left)
  range_between(offense.source_range.begin_pos - 1, left.source_range.end_pos - 1)
end

#reverse_index(collection, item) (private)

[ GitHub ]

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

def reverse_index(collection, item)
  collection.size - 1 - collection.reverse.index(item)
end

#splat_variable_before?(first_offense, variables) ⇒ Boolean (private)

[ GitHub ]

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

def splat_variable_before?(first_offense, variables)
  # Account for cases like `_, *rest, _`, where we would otherwise get
  # the index of the first underscore.
  first_offense_index = reverse_index(variables, first_offense)

  variables[0...first_offense_index].any?(&:splat_type?)
end

#unneeded_ranges(node) (private)

[ GitHub ]

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

def unneeded_ranges(node)
  node.masgn_type? ? (mlhs_node, = *node) : mlhs_node = node
  variables = *mlhs_node

  main_offense = main_node_offense(node)
  if main_offense.nil?
    children_offenses(variables)
  else
    children_offenses(variables) << main_offense
  end
end

#unused_range(node_type, mlhs_node, right) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_underscore_variable.rb', line 133

def unused_range(node_type, mlhs_node, right)
  start_range = mlhs_node.source_range.begin_pos

  end_range = case node_type
              when :masgn
                right.source_range.begin_pos
              when :mlhs
                mlhs_node.source_range.end_pos
              end

  range_between(start_range, end_range)
end

#unused_variables_only?(offense, variables) ⇒ Boolean (private)

[ GitHub ]

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

def unused_variables_only?(offense, variables)
  offense.source_range == variables.first.source_range
end