Class: RuboCop::Cop::Style::MapIntoArray

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: self, `::RuboCop::Cop::RangeHelp`, `::RuboCop::Cop::Base`, `::RuboCop::Cop::AutocorrectLogic`, `::RuboCop::Cop::IgnoredNode`, `::RuboCop::Util`, RuboCop::AST::Sexp
Inherits:	RuboCop::Cop::Base Object RuboCop::Cop::Base RuboCop::Cop::Style::MapIntoArray
Defined in:	lib/rubocop/cop/style/map_into_array.rb

Overview

Checks for usages of each with <<, push, or append which can be replaced by map.

If PreferredMethods is configured for map in Style/CollectionMethods, this cop uses the specified method for replacement.

Note	The return value of `Enumerable#each` is `self`, whereas the return value of `Enumerable#map` is an `Array`. They are not autocorrected when a return value could be used because these types differ.

Note

It only detects when the mapping destination is either: * a local variable initialized as an empty array and referred to only by the pushing operation; * or, if it is the single block argument to a [].tap block. This is because, if not, it’s challenging to statically guarantee that the mapping destination variable remains an empty array:

ret = []
src.each { |e| ret << e * 2 } # {<<} method may mutate {ret}

dest = []
src.each { |e| dest << transform(e, dest) } # {transform} method may mutate {dest}

Examples:

# bad
dest = []
src.each { |e| dest << e * 2 }
dest

# good
dest = src.map { |e| e * 2 }

# bad
[].tap do |dest|
  src.each { |e| dest << e * 2 }
end

# good
dest = src.map { |e| e * 2 }

# good - contains another operation
dest = []
src.each { |e| dest << e * 2; puts e }
dest

Cop Safety Information:

This cop is unsafe because not all objects that have an each method also have a map method (e.g. yard). Additionally, for calls with a block, not all objects that have a map method return an array (e.g. Enumerator::Lazy).

Constant Summary

MSG =
# File 'lib/rubocop/cop/style/map_into_array.rb', line 64

'Use `%<new_method_name>s` instead of `each` to map elements into an array.'

`::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

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

.joining_forces

`::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

#after_leaving_scope(scope, _variable_table)
#each_block_with_push?(node)
#empty_array_asgn?(node)
#empty_array_tap(node)
#lvar_ref?(node, name)
#on_block(node) (also: #on_numblock)
#on_numblock(node)

Alias for #on_block.
#suitable_argument_node?(node)
#correct_push_node(corrector, push_node) private
#correct_return_value_handling(corrector, block, dest_var) private
#dest_used_only_for_mapping?(block, dest_var, asgn) ⇒ Boolean private
#find_closest_assignment(block, dest_var) private
#find_dest_var(block) private
#new_method_name private
#offending_empty_array_tap?(node, dest_var) ⇒ Boolean private
#register_offense(block, dest_var, asgn) private
#remove_assignment(corrector, asgn) private
#remove_tap(corrector, node, block_node) private
#return_value_used?(node) ⇒ Boolean private

`::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

#disable_offense, #disable_offense_at_end_of_line, #disable_offense_before_and_after, #disable_offense_with_eol_or_surround_comment, #max_line_length,
#range_by_lines	Expand the given range to include all of any lines it covers.
#range_of_first_line, #range_overlaps_offense?, #string_continuation, #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

Class Method Details

.joining_forces

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 105


def self.joining_forces
  VariableForce
end

Instance Method Details

#after_leaving_scope(scope, _variable_table)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 109


def after_leaving_scope(scope, _variable_table)
  (@scopes ||= []) << scope
end

#correct_push_node(corrector, push_node) (private)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 213


def correct_push_node(corrector, push_node)
  range = push_node.source_range
  arg_range = push_node.first_argument.source_range

  corrector.remove(range_between(range.begin_pos, arg_range.begin_pos))
  corrector.remove(range_between(arg_range.end_pos, range.end_pos))
end

#correct_return_value_handling(corrector, block, dest_var) (private)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 221


def correct_return_value_handling(corrector, block, dest_var)
  next_node = block.right_sibling

  if lvar_ref?(next_node, dest_var.name)
    corrector.remove(range_with_surrounding_space(next_node.source_range, side: :left))
  end

  corrector.insert_before(block, "#{dest_var.name} = ")
end

#dest_used_only_for_mapping?(block, dest_var, asgn) ⇒ `Boolean` (private)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 156


def dest_used_only_for_mapping?(block, dest_var, asgn)
  range = asgn.source_range.join(block.source_range)

  asgn.parent.equal?(block.parent) &&
    dest_var.references.one? { |r| range.contains?(r.node.source_range) } &&
    dest_var.assignments.one? { |a| range.contains?(a.node.source_range) }
end

#each_block_with_push?(node)

[ GitHub ]

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


def_node_matcher :each_block_with_push?, <<-PATTERN
  [
    ^({begin kwbegin block} ...)
    ({block numblock} (send !{nil? self} :each) _
      (send (lvar _) {:<< :push :append} #suitable_argument_node?))
  ]
PATTERN

#empty_array_asgn?(node)

[ GitHub ]

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


def_node_matcher :empty_array_asgn?, <<~PATTERN
  (
    lvasgn _ {
      (array)
      (send (const {nil? cbase} :Array) :[])
      (send (const {nil? cbase} :Array) :new (array)?)
      (send nil? :Array (array))
    }
  )
PATTERN

#empty_array_tap(node)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 93


def_node_matcher :empty_array_tap, <<~PATTERN
  ^^$(
    block
      (send (array) :tap)
      (args (arg _))
      ...
  )
PATTERN

#find_closest_assignment(block, dest_var) (private)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 150


def find_closest_assignment(block, dest_var)
  dest_var.assignments.reverse_each.lazy.map(&:node).find do |node|
    node.source_range.end_pos < block.source_range.begin_pos
  end
end

#find_dest_var(block) (private)

[ GitHub ]

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


def find_dest_var(block)
  node = block.body.receiver
  name = node.children.first

  candidates = @scopes.lazy.filter_map { |s| s.variables[name] }
  candidates.find { |v| v.references.any? { |n| n.node.equal?(node) } }
end

#lvar_ref?(node, name)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 103


def_node_matcher :lvar_ref?, '(lvar %1)'

#new_method_name (private)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 181


def new_method_name
  default = 'map'
  alternative = config.for_cop('Style/CollectionMethods').dig('PreferredMethods', default)
  alternative || default
end

#offending_empty_array_tap?(node, dest_var) ⇒ `Boolean` (private)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 141


def offending_empty_array_tap?(node, dest_var)
  return false unless (tap_block_node = empty_array_tap(dest_var.declaration_node))

  # A `tap` block only offends if the array push is the only thing in it;
  # otherwise we cannot guarantee that the block variable is still an empty
  # array when pushed to.
  tap_block_node.body == node
end

#on_block(node) Also known as: #on_numblock

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 113


def on_block(node)
  return unless each_block_with_push?(node)

  dest_var = find_dest_var(node)

  if offending_empty_array_tap?(node, dest_var)
    asgn = dest_var.declaration_node
  else
    return unless (asgn = find_closest_assignment(node, dest_var))
    return unless empty_array_asgn?(asgn)
    return unless dest_used_only_for_mapping?(node, dest_var, asgn)
  end

  register_offense(node, dest_var, asgn)
end

#on_numblock(node)

Alias for #on_block.

[ GitHub ]

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


alias on_numblock on_block

#register_offense(block, dest_var, asgn) (private)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 164


def register_offense(block, dest_var, asgn)
  add_offense(block, message: format(MSG, new_method_name: new_method_name)) do |corrector|
    next if return_value_used?(block)

    corrector.replace(block.send_node.selector, new_method_name)

    if (tap_block_node = empty_array_tap(dest_var.declaration_node))
      remove_tap(corrector, block, tap_block_node)
    else
      remove_assignment(corrector, asgn)
    end

    correct_push_node(corrector, block.body)
    correct_return_value_handling(corrector, block, dest_var)
  end
end

#remove_assignment(corrector, asgn) (private)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 200


def remove_assignment(corrector, asgn)
  range = range_with_surrounding_space(asgn.source_range, side: :right)
  range = range_with_surrounding_space(range, side: :right, newlines: false)

  corrector.remove(range)
end

#remove_tap(corrector, node, block_node) (private)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 207


def remove_tap(corrector, node, block_node)
  range = range_between(block_node.source_range.begin_pos, node.source_range.begin_pos)
  corrector.remove(range)
  corrector.remove(range_with_surrounding_space(block_node.loc.end, side: :left))
end

#return_value_used?(node) ⇒ `Boolean` (private)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 187


def return_value_used?(node)
  parent = node.parent

  case parent&.type
  when nil
    false
  when :begin, :kwbegin
    !node.right_sibling && return_value_used?(parent)
  else
    !parent.respond_to?(:void_context?) || !parent.void_context?
  end
end

#suitable_argument_node?(node)

[ GitHub ]

# File 'lib/rubocop/cop/style/map_into_array.rb', line 67


def_node_matcher :suitable_argument_node?, <<-PATTERN
  !{splat forwarded-restarg forwarded-args (hash (forwarded-kwrestarg)) (block-pass nil?)}
PATTERN

Class: RuboCop::Cop::Style::MapIntoArray

Overview

Constant Summary

::RuboCop::Cop::Base - Inherited

::RuboCop::Cop::RangeHelp - Included

Class Attribute Summary

::RuboCop::Cop::AutoCorrector - Extended

::RuboCop::Cop::Base - Inherited

Class Method Summary

::RuboCop::Cop::Base - Inherited

::RuboCop::ExcludeLimit - Extended

Instance Attribute Summary

::RuboCop::Cop::Base - Inherited

::RuboCop::Cop::AutocorrectLogic - Included

Instance Method Summary

::RuboCop::Cop::RangeHelp - Included

::RuboCop::Cop::Base - Inherited

::RuboCop::Cop::AutocorrectLogic - Included

::RuboCop::Cop::IgnoredNode - Included

Constructor Details

Class Method Details

.joining_forces

Instance Method Details

#after_leaving_scope(scope, _variable_table)

#correct_push_node(corrector, push_node) (private)

#correct_return_value_handling(corrector, block, dest_var) (private)

#dest_used_only_for_mapping?(block, dest_var, asgn) ⇒ Boolean (private)

#each_block_with_push?(node)

#empty_array_asgn?(node)

#empty_array_tap(node)

#find_closest_assignment(block, dest_var) (private)

#find_dest_var(block) (private)

#lvar_ref?(node, name)

#new_method_name (private)

#offending_empty_array_tap?(node, dest_var) ⇒ Boolean (private)

#on_block(node) Also known as: #on_numblock

#on_numblock(node)

#register_offense(block, dest_var, asgn) (private)

#remove_assignment(corrector, asgn) (private)

#remove_tap(corrector, node, block_node) (private)

#return_value_used?(node) ⇒ Boolean (private)

#suitable_argument_node?(node)

`::RuboCop::Cop::Base` - Inherited

`::RuboCop::Cop::RangeHelp` - Included

`::RuboCop::Cop::AutoCorrector` - Extended

`::RuboCop::Cop::Base` - Inherited

`::RuboCop::Cop::Base` - Inherited

`::RuboCop::ExcludeLimit` - Extended

`::RuboCop::Cop::Base` - Inherited

`::RuboCop::Cop::AutocorrectLogic` - Included

`::RuboCop::Cop::RangeHelp` - Included

`::RuboCop::Cop::Base` - Inherited

`::RuboCop::Cop::AutocorrectLogic` - Included

`::RuboCop::Cop::IgnoredNode` - Included

#dest_used_only_for_mapping?(block, dest_var, asgn) ⇒ `Boolean` (private)

#offending_empty_array_tap?(node, dest_var) ⇒ `Boolean` (private)

#return_value_used?(node) ⇒ `Boolean` (private)