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Contents
# frozen_string_literal: true
module RuboCop
module Cop
module Rails
# This cop enforces the use of `pluck` over `map`.
#
# `pluck` can be used instead of `map` to extract a single key from each
# element in an enumerable. When called on an Active Record relation, it
# results in a more efficient query that only selects the necessary key.
#
# @example
# # bad
# Post.published.map { |post| post[:title] }
# [{ a: :b, c: :d }].collect { |el| el[:a] }
#
# # good
# Post.published.pluck(:title)
# [{ a: :b, c: :d }].pluck(:a)
class Pluck < Base
extend AutoCorrector
extend TargetRailsVersion
MSG = 'Prefer `pluck(:%<value>s)` over `%<current>s`.'
minimum_target_rails_version 5.0
def_node_matcher :pluck_candidate?, <<~PATTERN
({block numblock} (send _ {:map :collect}) $_argument (send (lvar $_element) :[] (sym $_value)))
PATTERN
def on_block(node)
pluck_candidate?(node) do |argument, element, value|
match = if node.block_type?
argument.children.first.source.to_sym == element
else # numblock
argument == 1 && element == :_1
end
next unless match
message = message(value, node)
add_offense(offense_range(node), message: message) do |corrector|
corrector.replace(offense_range(node), "pluck(:#{value})")
end
end
end
alias on_numblock on_block
private
def offense_range(node)
node.send_node.loc.selector.join(node.loc.end)
end
def message(value, node)
current = offense_range(node).source
format(MSG, value: value, current: current)
end
end
end
end
end
Version data entries
5 entries across 5 versions & 2 rubygems