class RuboCop::Cop::Performance::Sum
This cop identifies places where custom code finding the sum of elements in some Enumerable object can be replaced by `Enumerable#sum` method.
This cop can change auto-correction scope depending on the value of `SafeAutoCorrect`. Its auto-correction is marked as safe by default (`SafeAutoCorrect: true`) to prevent `TypeError` in auto-correced code when initial value is not specified as shown below:
- source,ruby
['a', 'b'].sum # => (String can't be coerced into Integer)
Therefore if initial value is not specified, unsafe auto-corrected will not occur.
If you always want to enable auto-correction, you can set `SafeAutoCorrect: false`.
- source,yaml
Performance/Sum:
SafeAutoCorrect: false
Please note that the auto-correction command line option will be changed from `rubocop -a` to `rubocop -A`, which includes unsafe auto-correction.
@example
# bad [1, 2, 3].inject(:+) # These bad cases with no initial value are unsafe and [1, 2, 3].inject(&:+) # will not be auto-correced by default. If you want to [1, 2, 3].reduce { |acc, elem| acc + elem } # auto-corrected, you can set `SafeAutoCorrect: false`. [1, 2, 3].reduce(10, :+) [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)
Constants
- MSG
- MSG_IF_NO_INIT_VALUE
- RESTRICT_ON_SEND
Public Instance Methods
# File lib/rubocop/cop/performance/sum.rb, line 89 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
# File lib/rubocop/cop/performance/sum.rb, line 82 def on_send(node) return if empty_array_literal?(node) handle_sum_candidate(node) handle_sum_map_candidate(node) end
Private Instance Methods
# File lib/rubocop/cop/performance/sum.rb, line 132 def array_literal?(node) receiver = node.children.first receiver&.literal? && receiver&.array_type? end
# File lib/rubocop/cop/performance/sum.rb, line 137 def autocorrect(corrector, init, range) return if init.empty? && safe_autocorrect? replacement = build_good_method(init) corrector.replace(range, replacement) end
# File lib/rubocop/cop/performance/sum.rb, line 145 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) dot = '.' if map.receiver corrector.replace(map_range, "#{dot}#{replacement}") end
# File lib/rubocop/cop/performance/sum.rb, line 221 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
# File lib/rubocop/cop/performance/sum.rb, line 188 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
# File lib/rubocop/cop/performance/sum.rb, line 194 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
# File lib/rubocop/cop/performance/sum.rb, line 207 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
# File lib/rubocop/cop/performance/sum.rb, line 170 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
# File lib/rubocop/cop/performance/sum.rb, line 181 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
# File lib/rubocop/cop/performance/sum.rb, line 127 def empty_array_literal?(node) receiver = node.children.first array_literal?(node) && receiver && receiver.children.empty? end
# File lib/rubocop/cop/performance/sum.rb, line 104 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
# File lib/rubocop/cop/performance/sum.rb, line 115 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
# File lib/rubocop/cop/performance/sum.rb, line 232 def method_call_with_args_range(node) if (receiver = node.receiver) receiver.source_range.end.join(node.source_range.end) else node.source_range end end
# File lib/rubocop/cop/performance/sum.rb, line 166 def sum_block_range(send, node) range_between(send.loc.selector.begin_pos, node.loc.end.end_pos) end
# File lib/rubocop/cop/performance/sum.rb, line 162 def sum_map_range(map, sum) range_between(map.loc.selector.begin_pos, sum.source_range.end.end_pos) end
# File lib/rubocop/cop/performance/sum.rb, line 158 def sum_method_range(node) range_between(node.loc.selector.begin_pos, node.loc.end.end_pos) end