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Contents
# frozen_string_literal: true
module RuboCop
module Cop
module Performance
# This cop identifies places where `caller[n]`
# can be replaced by `caller(n..n).first`.
#
# @example
# # bad
# caller[1]
# caller.first
# caller_locations[1]
# caller_locations.first
#
# # good
# caller(2..2).first
# caller(1..1).first
# caller_locations(2..2).first
# caller_locations(1..1).first
class Caller < Cop
MSG_BRACE = 'Use `%<method>s(%<n>d..%<n>d).first`' \
' instead of `%<method>s[%<m>d]`.'.freeze
MSG_FIRST = 'Use `%<method>s(%<n>d..%<n>d).first`' \
' instead of `%<method>s.first`.'.freeze
def_node_matcher :slow_caller?, <<-PATTERN
{
(send nil? {:caller :caller_locations})
(send nil? {:caller :caller_locations} int)
}
PATTERN
def_node_matcher :caller_with_scope_method?, <<-PATTERN
{
(send #slow_caller? :first)
(send #slow_caller? :[] int)
}
PATTERN
def on_send(node)
return unless caller_with_scope_method?(node)
add_offense(node)
end
private
def message(node)
method_name = node.receiver.method_name
caller_arg = node.receiver.first_argument
n = caller_arg ? int_value(caller_arg) : 1
if node.method_name == :[]
m = int_value(node.first_argument)
n += m
format(MSG_BRACE, n: n, m: m, method: method_name)
else
format(MSG_FIRST, n: n, method: method_name)
end
end
def int_value(node)
node.children[0]
end
end
end
end
end
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6,840 entries across 6,834 versions & 27 rubygems