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Contents
# frozen_string_literal: true
module RuboCop
module Cop
module Performance
# This cop checks for .times.map calls.
# In most cases such calls can be replaced
# with an explicit array creation.
#
# @example
# # bad
# 9.times.map do |i|
# i.to_s
# end
#
# # good
# Array.new(9) do |i|
# i.to_s
# end
class TimesMap < Cop
MESSAGE = 'Use `Array.new(%<count>s)` with a block ' \
'instead of `.times.%<map_or_collect>s`'.freeze
MESSAGE_ONLY_IF = 'only if `%<count>s` is always 0 or more'.freeze
def on_send(node)
check(node)
end
def on_block(node)
check(node)
end
def autocorrect(node)
map_or_collect, count = times_map_call(node)
replacement =
"Array.new(#{count.source}" \
"#{map_or_collect.arguments.map { |arg| ", #{arg.source}" }.join})"
lambda do |corrector|
corrector.replace(map_or_collect.loc.expression, replacement)
end
end
private
def check(node)
times_map_call(node) do |map_or_collect, count|
add_offense(node, message: message(map_or_collect, count))
end
end
def message(map_or_collect, count)
template = if count.literal?
MESSAGE + '.'
else
"#{MESSAGE} #{MESSAGE_ONLY_IF}."
end
format(template,
count: count.source,
map_or_collect: map_or_collect.method_name)
end
def_node_matcher :times_map_call, <<-PATTERN
{(block $(send (send $!nil? :times) {:map :collect}) ...)
$(send (send $!nil? :times) {:map :collect} (block_pass ...))}
PATTERN
end
end
end
end
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