lib/rubocop/cop/style/conditional_assignment.rb
# frozen_string_literal: true
module RuboCop
module Cop
module Style
# Helper module to provide common methods to classes needed for the
# ConditionalAssignment Cop.
module ConditionalAssignmentHelper
extend NodePattern::Macros
EQUAL = '='
END_ALIGNMENT = 'Layout/EndAlignment'
ALIGN_WITH = 'EnforcedStyleAlignWith'
KEYWORD = 'keyword'
# `elsif` branches show up in the `node` as an `else`. We need
# to recursively iterate over all `else` branches and consider all
# but the last `node` an `elsif` branch and consider the last `node`
# the actual `else` branch.
def expand_elses(branch)
elsif_branches = expand_elsif(branch)
else_branch = elsif_branches.any? ? elsif_branches.pop : branch
[elsif_branches, else_branch]
end
# `when` nodes contain the entire branch including the condition.
# We only need the contents of the branch, not the condition.
def expand_when_branches(when_branches)
when_branches.map(&:body)
end
def tail(branch)
branch.begin_type? ? Array(branch).last : branch
end
# rubocop:disable Metrics/AbcSize
def lhs(node)
case node.type
when :send
lhs_for_send(node)
when :op_asgn
"#{node.children[0].source} #{node.children[1]}= "
when :and_asgn, :or_asgn
"#{node.children[0].source} #{node.loc.operator.source} "
when :casgn
lhs_for_casgn(node)
when *ConditionalAssignment::VARIABLE_ASSIGNMENT_TYPES
"#{node.children[0]} = "
else
node.source
end
end
# rubocop:enable Metrics/AbcSize
def indent(cop, source)
conf = cop.config.for_cop(END_ALIGNMENT)
if conf[ALIGN_WITH] == KEYWORD
' ' * source.length
else
''
end
end
def end_with_eq?(sym)
sym.to_s.end_with?(EQUAL)
end
private
def expand_elsif(node, elsif_branches = [])
return [] if node.nil? || !node.if_type? || !node.elsif?
elsif_branches << node.if_branch
else_branch = node.else_branch
if else_branch&.if_type? && else_branch&.elsif?
expand_elsif(else_branch, elsif_branches)
else
elsif_branches << else_branch
end
end
def lhs_for_send(node)
receiver = node.receiver ? node.receiver.source : ''
if node.method?(:[]=)
indices = node.arguments[0...-1].map(&:source).join(', ')
"#{receiver}[#{indices}] = "
elsif node.setter_method?
"#{receiver}.#{node.method_name[0...-1]} = "
else
"#{receiver} #{node.method_name} "
end
end
def lhs_for_casgn(node)
namespace = node.children[0]
if namespace.nil? || namespace.cbase_type?
"#{namespace&.source}#{node.children[1]} = "
else
"#{namespace.source}::#{node.children[1]} = "
end
end
def setter_method?(method_name)
method_name.to_s.end_with?(EQUAL) && !%i[!= == === >= <=].include?(method_name)
end
def assignment_rhs_exist?(node)
parent = node.parent
return true unless parent
!(parent.mlhs_type? || parent.resbody_type?)
end
end
# Check for `if` and `case` statements where each branch is used for
# both the assignment and comparison of the same variable
# when using the return of the condition can be used instead.
#
# @example EnforcedStyle: assign_to_condition (default)
# # bad
# if foo
# bar = 1
# else
# bar = 2
# end
#
# case foo
# when 'a'
# bar += 1
# else
# bar += 2
# end
#
# if foo
# some_method
# bar = 1
# else
# some_other_method
# bar = 2
# end
#
# # good
# bar = if foo
# 1
# else
# 2
# end
#
# bar += case foo
# when 'a'
# 1
# else
# 2
# end
#
# bar << if foo
# some_method
# 1
# else
# some_other_method
# 2
# end
#
# @example EnforcedStyle: assign_inside_condition
# # bad
# bar = if foo
# 1
# else
# 2
# end
#
# bar += case foo
# when 'a'
# 1
# else
# 2
# end
#
# bar << if foo
# some_method
# 1
# else
# some_other_method
# 2
# end
#
# # good
# if foo
# bar = 1
# else
# bar = 2
# end
#
# case foo
# when 'a'
# bar += 1
# else
# bar += 2
# end
#
# if foo
# some_method
# bar = 1
# else
# some_other_method
# bar = 2
# end
class ConditionalAssignment < Base
include ConditionalAssignmentHelper
include ConfigurableEnforcedStyle
include IgnoredNode
extend AutoCorrector
MSG = 'Use the return of the conditional for variable assignment and comparison.'
ASSIGN_TO_CONDITION_MSG = 'Assign variables inside of conditionals'
VARIABLE_ASSIGNMENT_TYPES = %i[casgn cvasgn gvasgn ivasgn lvasgn].freeze
ASSIGNMENT_TYPES = VARIABLE_ASSIGNMENT_TYPES + %i[and_asgn or_asgn op_asgn masgn].freeze
LINE_LENGTH = 'Layout/LineLength'
ENABLED = 'Enabled'
MAX = 'Max'
SINGLE_LINE_CONDITIONS_ONLY = 'SingleLineConditionsOnly'
# The shovel operator `<<` does not have its own type. It is a `send`
# type.
# @!method assignment_type?(node)
def_node_matcher :assignment_type?, <<~PATTERN
{
#{ASSIGNMENT_TYPES.join(' ')}
(send _recv {:[]= :<< :=~ :!~ :<=> #end_with_eq? :< :>} ...)
}
PATTERN
ASSIGNMENT_TYPES.each do |type|
define_method :"on_#{type}" do |node|
return if part_of_ignored_node?(node)
return if node.parent&.shorthand_asgn?
check_assignment_to_condition(node)
end
end
def on_send(node)
return unless assignment_type?(node)
check_assignment_to_condition(node)
end
def on_if(node)
return unless style == :assign_to_condition
return if node.elsif?
else_branch = node.else_branch
elsif_branches, else_branch = expand_elses(else_branch)
return unless else_branch
branches = [node.if_branch, *elsif_branches, else_branch]
check_node(node, branches)
end
def on_case(node)
return unless style == :assign_to_condition
return unless node.else_branch
when_branches = expand_when_branches(node.when_branches)
branches = [*when_branches, node.else_branch]
check_node(node, branches)
end
def on_case_match(node)
return unless style == :assign_to_condition
return unless node.else_branch
in_pattern_branches = expand_when_branches(node.in_pattern_branches)
branches = [*in_pattern_branches, node.else_branch]
check_node(node, branches)
end
private
def check_assignment_to_condition(node)
return unless candidate_node?(node)
ignore_node(node)
assignment = assignment_node(node)
return unless candidate_condition?(assignment)
_condition, *branches, else_branch = *assignment
return unless else_branch
return if allowed_single_line?([*branches, else_branch])
add_offense(node, message: ASSIGN_TO_CONDITION_MSG) do |corrector|
autocorrect(corrector, node)
end
end
def candidate_node?(node)
style == :assign_inside_condition && assignment_rhs_exist?(node)
end
# @!method candidate_condition?(node)
def_node_matcher :candidate_condition?, '[{if case case_match} !#allowed_ternary?]'
def allowed_ternary?(assignment)
assignment.if_type? && assignment.ternary? && !include_ternary?
end
def allowed_single_line?(branches)
single_line_conditions_only? && branches.any?(&:begin_type?)
end
def assignment_node(node)
*_variable, assignment = *node
# ignore pseudo-assignments without rhs in for nodes
return if node.parent&.for_type?
assignment, = *assignment if assignment.begin_type? && assignment.children.one?
assignment
end
def move_assignment_outside_condition(corrector, node)
if node.case_type? || node.case_match_type?
CaseCorrector.correct(corrector, self, node)
elsif node.ternary?
TernaryCorrector.correct(corrector, node)
elsif node.if? || node.unless?
IfCorrector.correct(corrector, self, node)
end
end
def move_assignment_inside_condition(corrector, node)
*_assignment, condition = *node
if ternary_condition?(condition)
TernaryCorrector.move_assignment_inside_condition(corrector, node)
elsif condition.case_type? || condition.case_match_type?
CaseCorrector.move_assignment_inside_condition(corrector, node)
elsif condition.if_type?
IfCorrector.move_assignment_inside_condition(corrector, node)
end
end
def ternary_condition?(node)
[node, node.children.first].compact.any? { |n| n.if_type? && n.ternary? }
end
def lhs_all_match?(branches)
return true if branches.empty?
first_lhs = lhs(branches.first)
branches.all? { |branch| lhs(branch) == first_lhs }
end
def assignment_types_match?(*nodes)
return false unless assignment_type?(nodes.first)
nodes.map(&:type).uniq.one?
end
def check_node(node, branches)
return if allowed_ternary?(node)
return unless allowed_statements?(branches)
return if allowed_single_line?(branches)
return if correction_exceeds_line_limit?(node, branches)
add_offense(node) { |corrector| autocorrect(corrector, node) }
end
def autocorrect(corrector, node)
if assignment_type?(node)
move_assignment_inside_condition(corrector, node)
else
move_assignment_outside_condition(corrector, node)
end
end
def allowed_statements?(branches)
return false unless branches.all?
statements = branches.filter_map { |branch| tail(branch) }
lhs_all_match?(statements) && statements.none?(&:masgn_type?) &&
assignment_types_match?(*statements)
end
# If `Layout/LineLength` is enabled, we do not want to introduce an
# offense by autocorrecting this cop. Find the max configured line
# length. Find the longest line of condition. Remove the assignment
# from lines that contain the offending assignment because after
# correcting, this will not be on the line anymore. Check if the length
# of the longest line + the length of the corrected assignment is
# greater than the max configured line length
def correction_exceeds_line_limit?(node, branches)
return false unless line_length_cop_enabled?
assignment = lhs(tail(branches[0]))
longest_line_exceeds_line_limit?(node, assignment)
end
def longest_line_exceeds_line_limit?(node, assignment)
longest_line(node, assignment).length > max_line_length
end
def longest_line(node, assignment)
assignment_regex = /\s*#{Regexp.escape(assignment).gsub('\ ', '\s*')}/
lines = node.source.lines.map { |line| line.chomp.sub(assignment_regex, '') }
longest_line = lines.max_by(&:length)
assignment + longest_line
end
def line_length_cop_enabled?
config.for_cop(LINE_LENGTH)[ENABLED]
end
def max_line_length
config.for_cop(LINE_LENGTH)[MAX]
end
def single_line_conditions_only?
cop_config[SINGLE_LINE_CONDITIONS_ONLY]
end
def include_ternary?
cop_config['IncludeTernaryExpressions']
end
end
# Helper module to provide common methods to ConditionalAssignment
# correctors
module ConditionalCorrectorHelper
def remove_whitespace_in_branches(corrector, branch, condition, column)
branch.each_node do |child|
next if child.source_range.nil?
white_space = white_space_range(child, column)
corrector.remove(white_space) if white_space.source.strip.empty?
end
[condition.loc.else, condition.loc.end].each do |loc|
corrector.remove_preceding(loc, loc.column - column)
end
end
def white_space_range(node, column)
expression = node.source_range
begin_pos = expression.begin_pos - (expression.column - column - 2)
Parser::Source::Range.new(expression.source_buffer, begin_pos, expression.begin_pos)
end
def assignment(node)
*_, condition = *node
node.source_range.begin.join(condition.source_range.begin)
end
def correct_if_branches(corrector, cop, node)
if_branch, elsif_branches, else_branch = extract_tail_branches(node)
corrector.insert_before(node, lhs(if_branch))
replace_branch_assignment(corrector, if_branch)
correct_branches(corrector, elsif_branches)
replace_branch_assignment(corrector, else_branch)
corrector.insert_before(node.loc.end, indent(cop, lhs(if_branch)))
end
def replace_branch_assignment(corrector, branch)
_variable, *_operator, assignment = *branch
source = assignment.source
replacement = if assignment.array_type? && !assignment.bracketed?
"[#{source}]"
else
source
end
corrector.replace(branch, replacement)
end
def correct_branches(corrector, branches)
branches.each do |branch|
*_, assignment = *branch
corrector.replace(branch, assignment.source)
end
end
end
# Corrector to correct conditional assignment in ternary conditions.
class TernaryCorrector
class << self
include ConditionalAssignmentHelper
include ConditionalCorrectorHelper
def correct(corrector, node)
corrector.replace(node, correction(node))
end
def move_assignment_inside_condition(corrector, node)
*_var, rhs = *node
if_branch, else_branch = extract_branches(node)
assignment = assignment(node)
remove_parentheses(corrector, rhs) if Util.parentheses?(rhs)
corrector.remove(assignment)
move_branch_inside_condition(corrector, if_branch, assignment)
move_branch_inside_condition(corrector, else_branch, assignment)
end
private
def correction(node)
"#{lhs(node.if_branch)}#{ternary(node)}"
end
def ternary(node)
_variable, *_operator, if_rhs = *node.if_branch
_else_variable, *_operator, else_rhs = *node.else_branch
expr = "#{node.condition.source} ? #{if_rhs.source} : #{else_rhs.source}"
element_assignment?(node.if_branch) ? "(#{expr})" : expr
end
def element_assignment?(node)
node.send_type? && !node.method?(:[]=)
end
def extract_branches(node)
*_var, rhs = *node
condition, = *rhs if rhs.begin_type? && rhs.children.one?
_condition, if_branch, else_branch = *(condition || rhs)
[if_branch, else_branch]
end
def remove_parentheses(corrector, node)
corrector.remove(node.loc.begin)
corrector.remove(node.loc.end)
end
def move_branch_inside_condition(corrector, branch, assignment)
corrector.insert_before(branch, assignment.source)
end
end
end
# Corrector to correct conditional assignment in `if` statements.
class IfCorrector
class << self
include ConditionalAssignmentHelper
include ConditionalCorrectorHelper
def correct(corrector, cop, node)
correct_if_branches(corrector, cop, node)
end
def move_assignment_inside_condition(corrector, node)
column = node.source_range.column
*_var, condition = *node
assignment = assignment(node)
corrector.remove(assignment)
condition.branches.flatten.each do |branch|
move_branch_inside_condition(corrector, branch, condition, assignment, column)
end
end
private
def extract_tail_branches(node)
if_branch, *elsif_branches, else_branch = *node.branches
elsif_branches.map! { |branch| tail(branch) }
[tail(if_branch), elsif_branches, tail(else_branch)]
end
def move_branch_inside_condition(corrector, branch, condition,
assignment, column)
branch_assignment = tail(branch)
corrector.insert_before(branch_assignment, assignment.source)
remove_whitespace_in_branches(corrector, branch, condition, column)
return unless (branch_else = branch.parent.loc.else)
corrector.remove_preceding(branch_else, branch_else.column - column)
end
end
end
# Corrector to correct conditional assignment in `case` statements.
class CaseCorrector
class << self
include ConditionalAssignmentHelper
include ConditionalCorrectorHelper
def correct(corrector, cop, node)
when_branches, else_branch = extract_tail_branches(node)
corrector.insert_before(node, lhs(else_branch))
correct_branches(corrector, when_branches)
replace_branch_assignment(corrector, else_branch)
corrector.insert_before(node.loc.end, indent(cop, lhs(else_branch)))
end
def move_assignment_inside_condition(corrector, node)
column = node.source_range.column
*_var, condition = *node
assignment = assignment(node)
corrector.remove(assignment)
extract_branches(condition).flatten.each do |branch|
move_branch_inside_condition(corrector, branch, condition, assignment, column)
end
end
private
def extract_tail_branches(node)
when_branches, else_branch = extract_branches(node)
when_branches.map! { |branch| tail(branch) }
[when_branches, tail(else_branch)]
end
def extract_branches(case_node)
when_branches = if case_node.case_type?
expand_when_branches(case_node.when_branches)
else
expand_when_branches(case_node.in_pattern_branches)
end
[when_branches, case_node.else_branch]
end
def move_branch_inside_condition(corrector, branch, condition, assignment, column)
branch_assignment = tail(branch)
corrector.insert_before(branch_assignment, assignment.source)
remove_whitespace_in_branches(corrector, branch, condition, column)
parent_keyword = branch.parent.loc.keyword
corrector.remove_preceding(parent_keyword, parent_keyword.column - column)
end
end
end
end
end
end