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redundant_condition.rb
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redundant_condition.rb
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# frozen_string_literal: true
module RuboCop
module Cop
module Style
# This cop checks for unnecessary conditional expressions.
#
# @example
# # bad
# a = b ? b : c
#
# # good
# a = b || c
#
# @example
# # bad
# if b
# b
# else
# c
# end
#
# # good
# b || c
#
# # good
# if b
# b
# elsif cond
# c
# end
#
class RedundantCondition < Cop
include RangeHelp
MSG = 'Use double pipes `||` instead.'
REDUNDANT_CONDITION = 'This condition is not needed.'
def on_if(node)
return if node.elsif_conditional?
return unless offense?(node)
add_offense(node, location: range_of_offense(node))
end
def autocorrect(node)
lambda do |corrector|
if node.ternary?
correct_ternary(corrector, node)
elsif node.modifier_form? || !node.else_branch
corrector.replace(node, node.if_branch.source)
else
corrected = make_ternary_form(node)
corrector.replace(node, corrected)
end
end
end
private
def message(node)
if node.modifier_form? || !node.else_branch
REDUNDANT_CONDITION
else
MSG
end
end
def range_of_offense(node)
return :expression unless node.ternary?
range_between(node.loc.question.begin_pos, node.loc.colon.end_pos)
end
def offense?(node)
condition, if_branch, else_branch = *node
return false if use_if_branch?(else_branch)
condition == if_branch && !node.elsif? && (
node.ternary? ||
!else_branch.instance_of?(AST::Node) ||
else_branch.single_line?
)
end
def use_if_branch?(else_branch)
else_branch&.if_type?
end
def else_source(else_branch)
if require_parentheses?(else_branch)
"(#{else_branch.source})"
elsif without_argument_parentheses_method?(else_branch)
"#{else_branch.method_name}(#{else_branch.arguments.map(&:source).join(', ')})"
else
else_branch.source
end
end
def make_ternary_form(node)
_condition, if_branch, else_branch = *node
ternary_form = [if_branch.source,
else_source(else_branch)].join(' || ')
if node.parent&.send_type?
"(#{ternary_form})"
else
ternary_form
end
end
def correct_ternary(corrector, node)
corrector.replace(range_of_offense(node), '||')
return unless node.else_branch.range_type?
corrector.wrap(node.else_branch, '(', ')')
end
def require_parentheses?(node)
node.basic_conditional? &&
node.modifier_form? ||
node.range_type? ||
node.rescue_type? ||
node.respond_to?(:semantic_operator?) && node.semantic_operator?
end
def without_argument_parentheses_method?(node)
node.send_type? && !node.arguments.empty? && !node.parenthesized?
end
end
end
end
end