depend on Zeitwerk 2

Gemfile.lock

@@ -71,7 +71,7 @@ PATH
       i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-      zeitwerk (~> 1.4, >= 1.4.3)
+      zeitwerk (~> 2.0)
     rails (6.0.0.beta3)
       actioncable (= 6.0.0.beta3)
       actionmailbox (= 6.0.0.beta3)
@@ -526,7 +526,7 @@ GEM
     websocket-extensions (0.1.3)
     xpath (3.2.0)
       nokogiri (~> 1.8)
-    zeitwerk (1.4.3)
+    zeitwerk (2.0.0)
 
 PLATFORMS
   java

activesupport/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Depends on Zeitwerk 2, which stores less metadata if reloading is disabled
+    and hence uses less memory when `config.cache_classes` is `true`, a standard
+    setup in production.
+
+    *Xavier Noria*
+
 *   In `:zeitwerk` mode, eager load directories in engines and applications only
     if present in their respective `config.eager_load_paths`.
 

activesupport/activesupport.gemspec

@@ -34,5 +34,5 @@ Gem::Specification.new do |s|
   s.add_dependency "tzinfo",          "~> 1.1"
   s.add_dependency "minitest",        "~> 5.1"
   s.add_dependency "concurrent-ruby", "~> 1.0", ">= 1.0.2"
-  s.add_dependency "zeitwerk",        "~> 1.4", ">= 1.4.3"
+  s.add_dependency "zeitwerk",        "~> 2.0"
 end

activesupport/lib/active_support/dependencies/zeitwerk_integration.rb

@@ -51,15 +51,15 @@ module ActiveSupport
       end
 
       class << self
-        def take_over
-          setup_autoloaders
+        def take_over(enable_reloading:)
+          setup_autoloaders(enable_reloading)
           freeze_paths
           decorate_dependencies
         end
 
         private
 
-          def setup_autoloaders
+          def setup_autoloaders(enable_reloading)
             Dependencies.autoload_paths.each do |autoload_path|
               # Zeitwerk only accepts existing directories in `push_dir` to
               # prevent misconfigurations.
@@ -72,6 +72,7 @@ module ActiveSupport
               autoloader.do_not_eager_load(autoload_path) unless eager_load?(autoload_path)
             end
 
+            Rails.autoloaders.main.enable_reloading if enable_reloading
             Rails.autoloaders.each(&:setup)
           end
 

railties/lib/rails/application/finisher.rb

@@ -24,7 +24,7 @@ module Rails
       initializer :let_zeitwerk_take_over do
         if config.autoloader == :zeitwerk
           require "active_support/dependencies/zeitwerk_integration"
-          ActiveSupport::Dependencies::ZeitwerkIntegration.take_over
+          ActiveSupport::Dependencies::ZeitwerkIntegration.take_over(enable_reloading: !config.cache_classes)
         end
       end
 

railties/test/application/zeitwerk_integration_test.rb

@@ -131,6 +131,20 @@ class ZeitwerkIntegrationTest < ActiveSupport::TestCase
     assert $zeitwerk_integration_test_post
   end
 
+  test "reloading is enabled if config.cache_classes is false" do
+    boot
+
+    assert     Rails.autoloaders.main.reloading_enabled?
+    assert_not Rails.autoloaders.once.reloading_enabled?
+  end
+
+  test "reloading is disabled if config.cache_classes is true" do
+    boot("production")
+
+    assert_not Rails.autoloaders.main.reloading_enabled?
+    assert_not Rails.autoloaders.once.reloading_enabled?
+  end
+
   test "eager loading loads code in engines" do
     $test_blog_engine_eager_loaded = false