/
identical_conditional_branches.rb
130 lines (116 loc) · 3 KB
/
identical_conditional_branches.rb
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# frozen_string_literal: true
module RuboCop
module Cop
module Style
# This cop checks for identical lines at the beginning or end of
# each branch of a conditional statement.
#
# @example
# # bad
# if condition
# do_x
# do_z
# else
# do_y
# do_z
# end
#
# # good
# if condition
# do_x
# else
# do_y
# end
# do_z
#
# # bad
# if condition
# do_z
# do_x
# else
# do_z
# do_y
# end
#
# # good
# do_z
# if condition
# do_x
# else
# do_y
# end
#
# # bad
# case foo
# when 1
# do_x
# when 2
# do_x
# else
# do_x
# end
#
# # good
# case foo
# when 1
# do_x
# do_y
# when 2
# # nothing
# else
# do_x
# do_z
# end
class IdenticalConditionalBranches < Cop
MSG = 'Move `%<source>s` out of the conditional.'
def on_if(node)
return if node.elsif?
branches = expand_elses(node.else_branch).unshift(node.if_branch)
check_branches(branches)
end
def on_case(node)
return unless node.else? && node.else_branch
branches = node.when_branches.map(&:body).push(node.else_branch)
check_branches(branches)
end
private
def check_branches(branches) # rubocop:todo Metrics/CyclomaticComplexity
# return if any branch is empty. An empty branch can be an `if`
# without an `else` or a branch that contains only comments.
return if branches.any?(&:nil?)
tails = branches.map { |branch| tail(branch) }
check_expressions(tails) if tails.none?(&:nil?)
heads = branches.map { |branch| head(branch) }
check_expressions(heads) if tails.none?(&:nil?)
end
def check_expressions(expressions)
return unless expressions.size > 1 && expressions.uniq.one?
expressions.each do |expression|
add_offense(expression)
end
end
def message(node)
format(MSG, source: node.source)
end
# `elsif` branches show up in the if node as nested `else` branches. We
# need to recursively iterate over all `else` branches.
def expand_elses(branch)
if branch.nil?
[nil]
elsif branch.if_type?
_condition, elsif_branch, else_branch = *branch
expand_elses(else_branch).unshift(elsif_branch)
else
[branch]
end
end
def tail(node)
node.begin_type? ? node.children.last : node
end
def head(node)
node.begin_type? ? node.children.first : node
end
end
end
end
end