Add new ZipForArrayWrapping cop

changelog/new_merge_pull_request_462_from.md

@@ -0,0 +1 @@
+* [#462](https://github.com/rubocop/rubocop-performance/pull/462): Add new `Performance/ZipForArrayWrapping` cop that checks patterns like `.map { |id| [id] }` or `.map { [_1] }` and can safely replace them with `.zip`. ([@corsonknowles][])

config/default.yml

@@ -372,3 +372,8 @@ Performance/UriDefaultParser:
   Description: 'Use `URI::DEFAULT_PARSER` instead of `URI::Parser.new`.'
   Enabled: true
   VersionAdded: '0.50'
+
+Performance/ZipForArrayWrapping:
+  Description: 'Checks for `.map { |id| [id] }` and suggests replacing it with `.zip`.'
+  Enabled: pending
+  VersionAdded: <<next>>

lib/rubocop/cop/performance/zip_for_array_wrapping.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Performance
+      # Checks for `.map { |id| [id] }` and suggests replacing it with `.zip`.
+      #
+      # @example
+      #   # bad
+      #   [1, 2, 3].map { |id| [id] }
+      #
+      #   # bad
+      #   [1, 2, 3].map { [_1] }
+      #
+      #   # good
+      #   [1, 2, 3].zip
+      #
+      # @example
+      #   # good (no offense)
+      #   [1, 2, 3].map { |id| id }
+      #
+      # @example
+      #   # good (no offense)
+      #   [1, 2, 3].map { |id| [id, id] }
+      class ZipForArrayWrapping < Base
+        include RangeHelp
+        extend AutoCorrector
+
+        MSG = 'Use `zip` instead of `%<original_code>s`.'
+        RESTRICT_ON_SEND = Set.new(%i[map collect]).freeze
+
+        # Matches regular block form `.map { |e| [e] }`
+        # @!method map_with_array?(node)
+        def_node_matcher :map_with_array?, <<~PATTERN
+          (block
+            (send _ RESTRICT_ON_SEND)
+            (args (arg _id))
+            (array (lvar _id)))
+        PATTERN
+
+        # Matches numblock form `.map { [_1] }`
+        # @!method map_with_array_numblock?(node)
+        def_node_matcher :map_with_array_numblock?, <<~PATTERN
+          (numblock
+            (send _ :map)
+            1
+            (array (lvar _))
+          )
+        PATTERN
+
+        def on_send(node)
+          return unless (parent = node.parent)
+          return unless map_with_array?(parent) || map_with_array_numblock?(parent)
+          return unless (receiver = node.receiver&.source)
+
+          register_offense(parent, receiver, node)
+        end
+
+        private
+
+        def register_offense(parent, receiver, node)
+          add_offense(offense_range(parent), message: message(node)) do |corrector|
+            autocorrect(parent, receiver, corrector)
+          end
+        end
+
+        def message(node)
+          format(MSG, original_code: offense_range(node).source.lines.first.chomp)
+        end
+
+        def autocorrect(parent, receiver, corrector)
+          corrector.replace(parent, "#{receiver}.zip")
+        end
+
+        def offense_range(node)
+          @offense_range ||= range_between(node.children.first.loc.selector.begin_pos, node.loc.end.end_pos)
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/performance_cops.rb

@@ -53,3 +53,4 @@
 require_relative 'performance/unfreeze_string'
 require_relative 'performance/uri_default_parser'
 require_relative 'performance/chain_array_allocation'
+require_relative 'performance/zip_for_array_wrapping'