/
sum.rb
212 lines (176 loc) · 6.76 KB
/
sum.rb
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# frozen_string_literal: true
module RuboCop
module Cop
module Performance
# This cop identifies places where custom code finding the sum of elements
# in some Enumerable object can be replaced by `Enumerable#sum` method.
#
# @example
# # bad
# [1, 2, 3].inject(:+)
# [1, 2, 3].reduce(10, :+)
# [1, 2, 3].inject(&:+)
# [1, 2, 3].reduce { |acc, elem| acc + elem }
# [1, 2, 3].map { |elem| elem ** 2 }.sum
# [1, 2, 3].collect(&:count).sum(10)
#
# # good
# [1, 2, 3].sum
# [1, 2, 3].sum(10)
# [1, 2, 3].sum { |elem| elem ** 2 }
# [1, 2, 3].sum(10, &:count)
#
class Sum < Base
include RangeHelp
extend AutoCorrector
MSG = 'Use `%<good_method>s` instead of `%<bad_method>s`.'
MSG_IF_NO_INIT_VALUE =
'Use `%<good_method>s` instead of `%<bad_method>s`, unless calling `%<bad_method>s` on an empty array.'
RESTRICT_ON_SEND = %i[inject reduce sum].freeze
def_node_matcher :sum_candidate?, <<~PATTERN
(send _ ${:inject :reduce} $_init ? ${(sym :+) (block_pass (sym :+))})
PATTERN
def_node_matcher :sum_map_candidate?, <<~PATTERN
(send
{
(block $(send _ {:map :collect}) ...)
$(send _ {:map :collect} (block_pass _))
}
:sum $_init ?)
PATTERN
def_node_matcher :sum_with_block_candidate?, <<~PATTERN
(block
$(send _ {:inject :reduce} $_init ?)
(args (arg $_acc) (arg $_elem))
$send)
PATTERN
def_node_matcher :acc_plus_elem?, <<~PATTERN
(send (lvar %1) :+ (lvar %2))
PATTERN
alias elem_plus_acc? acc_plus_elem?
def on_send(node)
return if empty_array_literal?(node)
handle_sum_candidate(node)
handle_sum_map_candidate(node)
end
def on_block(node)
sum_with_block_candidate?(node) do |send, init, var_acc, var_elem, body|
if acc_plus_elem?(body, var_acc, var_elem) || elem_plus_acc?(body, var_elem, var_acc)
range = sum_block_range(send, node)
message = build_block_message(send, init, var_acc, var_elem, body)
add_offense(range, message: message) do |corrector|
autocorrect(corrector, init, range)
end
end
end
end
private
def handle_sum_candidate(node)
sum_candidate?(node) do |method, init, operation|
range = sum_method_range(node)
message = build_method_message(node, method, init, operation)
add_offense(range, message: message) do |corrector|
autocorrect(corrector, init, range)
end
end
end
def handle_sum_map_candidate(node)
sum_map_candidate?(node) do |map, init|
next if node.block_literal? || node.block_argument?
message = build_sum_map_message(map.method_name, init)
add_offense(sum_map_range(map, node), message: message) do |corrector|
autocorrect_sum_map(corrector, node, map, init)
end
end
end
def empty_array_literal?(node)
receiver = node.children.first
array_literal?(node) && receiver && receiver.children.empty?
end
def array_literal?(node)
receiver = node.children.first
receiver&.literal? && receiver&.array_type?
end
def autocorrect(corrector, init, range)
return if init.empty?
replacement = build_good_method(init)
corrector.replace(range, replacement)
end
def autocorrect_sum_map(corrector, sum, map, init)
sum_range = method_call_with_args_range(sum)
map_range = method_call_with_args_range(map)
block_pass = map.last_argument if map.last_argument&.block_pass_type?
replacement = build_good_method(init, block_pass)
corrector.remove(sum_range)
corrector.replace(map_range, ".#{replacement}")
end
def sum_method_range(node)
range_between(node.loc.selector.begin_pos, node.loc.end.end_pos)
end
def sum_map_range(map, sum)
range_between(map.loc.selector.begin_pos, sum.source_range.end.end_pos)
end
def sum_block_range(send, node)
range_between(send.loc.selector.begin_pos, node.loc.end.end_pos)
end
def build_method_message(node, method, init, operation)
good_method = build_good_method(init)
bad_method = build_method_bad_method(init, method, operation)
msg = if init.empty? && !array_literal?(node)
MSG_IF_NO_INIT_VALUE
else
MSG
end
format(msg, good_method: good_method, bad_method: bad_method)
end
def build_sum_map_message(method, init)
sum_method = build_good_method(init)
good_method = "#{sum_method} { ... }"
bad_method = "#{method} { ... }.#{sum_method}"
format(MSG, good_method: good_method, bad_method: bad_method)
end
def build_block_message(send, init, var_acc, var_elem, body)
good_method = build_good_method(init)
bad_method = build_block_bad_method(send.method_name, init, var_acc, var_elem, body)
format(MSG, good_method: good_method, bad_method: bad_method)
end
def build_good_method(init, block_pass = nil)
good_method = 'sum'
args = []
unless init.empty?
init = init.first
args << init.source unless init.int_type? && init.value.zero?
end
args << block_pass.source if block_pass
good_method += "(#{args.join(', ')})" unless args.empty?
good_method
end
def build_method_bad_method(init, method, operation)
bad_method = "#{method}("
unless init.empty?
init = init.first
bad_method += "#{init.source}, "
end
bad_method += if operation.block_pass_type?
'&:+)'
else
':+)'
end
bad_method
end
def build_block_bad_method(method, init, var_acc, var_elem, body)
bad_method = method.to_s
unless init.empty?
init = init.first
bad_method += "(#{init.source})"
end
bad_method += " { |#{var_acc}, #{var_elem}| #{body.source} }"
bad_method
end
def method_call_with_args_range(node)
node.receiver.source_range.end.join(node.source_range.end)
end
end
end
end
end