Add new Performance/ShortCircuitAnd cop

changelog/new_short_circuit_and_for_cost_effective_evaluation.md

@@ -0,0 +1 @@
+* [#505](https://github.com/rubocop/rubocop-performance/issues/505): Add a new cop to enforce short-circuiting of logical `and`s by evaluating cheaper expressions first. ([@Am1ne77][])

config/default.yml

@@ -294,6 +294,13 @@ Performance/SelectMap:
   Enabled: false
   VersionAdded: '1.11'
 
+Performance/ShortCircuitAnd:
+  Description: >-
+                  Use Ruby's short-circuiting behavior to evaluate cheaper
+                  expressions before expensive ones in `and` operations.
+  Enabled: 'pending'
+  VersionAdded: <<next>>
+
 Performance/Size:
   Description: >-
                   Use `size` instead of `count` for counting

lib/rubocop/cop/performance/short_circuit_and.rb

@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Performance
+      # Identifies logical expressions where a cheaper operand
+      # appears after a more expensive one (like a method call) in `and`/`&&` expressions.
+      #
+      # Reordering such expressions improves performance by leveraging Ruby's short-circuiting
+      # behavior ensuring inexpensive checks are evaluated first.
+      #
+      # @example
+      #   # bad
+      #   costly_method? && local_var
+      #
+      #   # good
+      #   local_var && costly_method?
+      class ShortCircuitAnd < Base
+        extend AutoCorrector
+
+        MSG = 'Use short-circuit logic with cheaper expressions first to avoid unnecessary method calls.'
+
+        def on_and(and_node)
+          if and_node.children.first.and_type? && and_node.children[1].variable?
+            handle_child_and(and_node)
+          elsif !and_node.children.first.variable? && and_node.children[1].variable?
+            handle_leaf(and_node)
+          end
+        end
+
+        def handle_child_and(and_node)
+          top_and_node = and_node
+          var_node = and_node.children[1]
+          loop do
+            and_node = and_node.children.first
+            unless and_node.children[1].variable?
+              add_offense(top_and_node) do |corrector|
+                corrector.swap(var_node, and_node.children[1])
+              end
+            end
+            break unless and_node.children.first.and_type?
+          end
+        end
+
+        def handle_leaf(and_node)
+          add_offense(and_node) do |corrector|
+            corrector.swap(and_node.children.first, and_node.children[1])
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/performance/sum.rb

@@ -154,7 +154,7 @@ def handle_sum_map_candidate(node)
 
         def empty_array_literal?(node)
           receiver = node.children.first
-          array_literal?(node) && receiver && receiver.children.empty?
+          receiver && array_literal?(node) && receiver.children.empty?
         end
 
         def array_literal?(node)

lib/rubocop/cop/performance_cops.rb

@@ -41,6 +41,7 @@
 require_relative 'performance/reverse_each'
 require_relative 'performance/reverse_first'
 require_relative 'performance/select_map'
+require_relative 'performance/short_circuit_and'
 require_relative 'performance/size'
 require_relative 'performance/sort_reverse'
 require_relative 'performance/squeeze'

spec/rubocop/cop/performance/short_circuit_and_spec.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Performance::ShortCircuitAnd, :config do
+  defs = <<~RUBY
+    a = 42
+    def foo?
+      42
+    end
+  RUBY
+
+  shared_examples 'logical_and' do |logical_and|
+    it "registers an offense for a single misordered use of `#{logical_and}`" do
+      expect_offense(<<~RUBY, logical_and: logical_and)
+        #{defs}
+        foo? #{logical_and} a
+        ^^^^^^{logical_and}^^ Use short-circuit logic with cheaper expressions first to avoid unnecessary method calls.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        #{defs}
+        a #{logical_and} foo?
+      RUBY
+    end
+
+    it "doesn't register an offense for a single well ordered use of `#{logical_and}`" do
+      expect_no_offenses(<<~RUBY)
+        #{defs}
+        a #{logical_and} foo?
+      RUBY
+    end
+
+    it "registers offenses for multiple misordered uses of `#{logical_and}`" do
+      expect_offense(<<~RUBY, logical_and: logical_and)
+        #{defs}
+        foo? #{logical_and} a #{logical_and} foo? #{logical_and} a
+        ^^^^^^{logical_and}^^ Use short-circuit logic with cheaper expressions first to avoid unnecessary method calls.
+        ^^^^^^{logical_and}^^^^{logical_and}^^^^^^^{logical_and}^^ Use short-circuit logic with cheaper expressions first to avoid unnecessary method calls.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        #{defs}
+        a #{logical_and} a #{logical_and} foo? #{logical_and} foo?
+      RUBY
+    end
+
+    it "doesn't register offenses for multiple misordered uses of `#{logical_and}`" do
+      expect_no_offenses(<<~RUBY)
+        #{defs}
+        a #{logical_and} a #{logical_and} foo? #{logical_and} foo?
+      RUBY
+    end
+  end
+
+  include_examples 'logical_and', '&&'
+  include_examples 'logical_and', 'and'
+end