Add Rails/EnvLocal cop

Enforces the use of `Rails.env.local?` instead of
`Rails.env.development? || Rails.env.test?`, as of Rails 7.1.

changelog/new_add_railsenvlocal_cop.md

@@ -0,0 +1 @@
+* [#906](https://github.com/rubocop/rubocop-rails/pull/906): Add `Rails/EnvLocal` cop. ([@sambostock][])

config/default.yml

@@ -430,6 +430,11 @@ Rails/EnumUniqueness:
   Include:
     - app/models/**/*.rb
 
+Rails/EnvLocal:
+  Description: 'Use `Rails.env.local?` instead of `Rails.env.development? || Rails.env.test?`.'
+  Enabled: pending
+  VersionAdded: '<<next>>'
+
 Rails/EnvironmentComparison:
   Description: "Favor `Rails.env.production?` over `Rails.env == 'production'`."
   Enabled: true

lib/rubocop/cop/rails/env_local.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Rails
+      # Checks for usage of `Rails.env.development? || Rails.env.test?` which
+      # can be replaced with `Rails.env.local?`, introduced in Rails 7.1.
+      #
+      # @example
+      #
+      #   # bad
+      #   Rails.env.development? || Rails.env.test?
+      #
+      #   # good
+      #   Rails.env.local?
+      #
+      class EnvLocal < Base
+        extend AutoCorrector
+        extend TargetRailsVersion
+
+        MSG = 'Use `Rails.env.local?` instead.'
+        LOCAL_ENVIRONMENTS = %i[development? test?].to_set.freeze
+
+        minimum_target_rails_version 7.1
+
+        # @!method rails_env_local_candidate?(node)
+        def_node_matcher :rails_env_local_candidate?, <<~PATTERN
+          (or
+            (send (send (const {cbase nil? } :Rails) :env) $%LOCAL_ENVIRONMENTS)
+            (send (send (const {cbase nil? } :Rails) :env) $%LOCAL_ENVIRONMENTS)
+          )
+        PATTERN
+
+        def on_or(node)
+          rails_env_local_candidate?(node) do |*environments|
+            next unless environments.to_set == LOCAL_ENVIRONMENTS
+
+            add_offense(node) do |corrector|
+              corrector.replace(node, 'Rails.env.local?')
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rails_cops.rb

@@ -46,6 +46,7 @@
 require_relative 'rails/eager_evaluation_log_message'
 require_relative 'rails/enum_hash'
 require_relative 'rails/enum_uniqueness'
+require_relative 'rails/env_local'
 require_relative 'rails/environment_comparison'
 require_relative 'rails/environment_variable_access'
 require_relative 'rails/exit'

spec/rubocop/cop/rails/env_local_spec.rb

@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Rails::EnvLocal, :config do
+  shared_examples 'non-local candidates' do
+    it 'registers no offenses for non-local `Rails.env._? || Rails.env._?`' do
+      expect_no_offenses(<<~RUBY)
+        Rails.env.development? || Rails.env.production?
+        Rails.env.test? || Rails.env.production?
+        Rails.env.production? || Rails.env.other?
+      RUBY
+    end
+
+    it 'registers no offenses for single `Rails.env._?`' do
+      expect_no_offenses(<<~RUBY)
+        Rails.env.development?
+        Rails.env.test?
+        Rails.env.production?
+        Rails.env.other?
+      RUBY
+    end
+  end
+
+  context 'In Rails >= 7.1', :rails71 do
+    it 'registers an offense for `Rails.env.development? || Rails.env.test?`' do
+      expect_offense(<<~RUBY)
+        Rails.env.development? || Rails.env.test?
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `Rails.env.local?` instead.
+        Rails.env.test? || Rails.env.development?
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `Rails.env.local?` instead.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        Rails.env.local?
+        Rails.env.local?
+      RUBY
+    end
+
+    it 'registers no offenses for `Rails.env.local?`' do
+      expect_no_offenses(<<~RUBY)
+        Rails.env.local?
+      RUBY
+    end
+
+    include_examples 'non-local candidates'
+  end
+
+  context 'In Rails < 7.1', :rails70 do
+    it 'registers no offenses for `Rails.env.development? || Rails.env.test?`' do
+      expect_no_offenses(<<~RUBY)
+        Rails.env.development? || Rails.env.test?
+        Rails.env.test? || Rails.env.development?
+      RUBY
+    end
+
+    it 'registers no offenses for `Rails.env.local?`' do
+      expect_no_offenses(<<~RUBY)
+        Rails.env.local?
+      RUBY
+    end
+
+    include_examples 'non-local candidates'
+  end
+end