Merge pull request #462 from corsonknowles/add_performance_use_zip_to…

…_wrap_arrays

Add new `ZipWithoutBlock` cop

changelog/new_merge_pull_request_462_from.md

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

config/default.yml

@@ -381,3 +381,9 @@ Performance/UriDefaultParser:
   Description: 'Use `URI::DEFAULT_PARSER` instead of `URI::Parser.new`.'
   Enabled: true
   VersionAdded: '0.50'
+
+Performance/ZipWithoutBlock:
+  Description: 'Checks for `map { |id| [id] }` and suggests replacing it with `zip`.'
+  Enabled: pending
+  Safe: false
+  VersionAdded: <<next>>

lib/rubocop/cop/performance/zip_without_block.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Performance
+      # Checks for `map { |id| [id] }` and suggests replacing it with `zip`.
+      #
+      # @safety
+      #   This cop is unsafe for novel definitions of `map` and `collect`
+      #   on non-Enumerable objects that do not respond to `zip`.
+      #   To make your object enumerable, define an `each` method
+      #   as described in https://ruby-doc.org/core/Enumerable.html
+      #
+      # @example
+      #   # bad
+      #   [1, 2, 3].map { |id| [id] }
+      #
+      #   # good
+      #   [1, 2, 3].zip
+      class ZipWithoutBlock < Base
+        extend AutoCorrector
+
+        MSG = 'Use `zip` without a block argument instead.'
+        RESTRICT_ON_SEND = Set.new(%i[map collect]).freeze
+
+        # @!method map_with_array?(node)
+        def_node_matcher :map_with_array?, <<~PATTERN
+          {
+            (block (call !nil? RESTRICT_ON_SEND) (args (arg _)) (array (lvar _)))
+            (numblock (call !nil? RESTRICT_ON_SEND) 1 (array (lvar _)))
+          }
+        PATTERN
+
+        def on_send(node)
+          return unless map_with_array?(node.parent)
+
+          register_offense(node)
+        end
+        alias on_csend on_send
+
+        private
+
+        def register_offense(node)
+          offense_range = offense_range(node)
+          add_offense(offense_range) do |corrector|
+            corrector.replace(offense_range, 'zip')
+          end
+        end
+
+        def offense_range(node)
+          node.loc.selector.join(node.parent.loc.end)
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/performance_cops.rb

@@ -54,3 +54,4 @@
 require_relative 'performance/unfreeze_string'
 require_relative 'performance/uri_default_parser'
 require_relative 'performance/chain_array_allocation'
+require_relative 'performance/zip_without_block'