upgrades Zeitwerk to 2.1.4

This commit more or less undoes 9b5401f, restores autoloaded? not to
touch the descendants tracker, and autoloaded_constants because it is
documented in the guide.

Gemfile.lock

@@ -71,7 +71,7 @@ PATH
       i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-      zeitwerk (~> 2.1, >= 2.1.2)
+      zeitwerk (~> 2.1, >= 2.1.4)
     rails (6.0.0.beta3)
       actioncable (= 6.0.0.beta3)
       actionmailbox (= 6.0.0.beta3)
@@ -528,7 +528,7 @@ GEM
     websocket-extensions (0.1.3)
     xpath (3.2.0)
       nokogiri (~> 1.8)
-    zeitwerk (2.1.2)
+    zeitwerk (2.1.4)
 
 PLATFORMS
   java

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",        "~> 2.1", ">= 2.1.2"
+  s.add_dependency "zeitwerk",        "~> 2.1", ">= 2.1.4"
 end

activesupport/lib/active_support/dependencies/zeitwerk_integration.rb

@@ -23,8 +23,13 @@ module ActiveSupport
           ActiveSupport::Inflector.safe_constantize(cpath)
         end
 
-        def to_unload?(cpath)
-          Rails.autoloaders.main.to_unload?(cpath)
+        def autoloaded_constants
+          Rails.autoloaders.main.unloadable_cpaths
+        end
+
+        def autoloaded?(object)
+          cpath = object.is_a?(Module) ? object.name : object.to_s
+          Rails.autoloaders.main.unloadable_cpath?(cpath)
         end
 
         def verbose=(verbose)

activesupport/lib/active_support/descendants_tracker.rb

@@ -22,18 +22,11 @@ module ActiveSupport
 
       def clear
         if defined? ActiveSupport::Dependencies
-          # to_unload? is only defined in Zeitwerk mode.
-          to_unload = if Dependencies.respond_to?(:to_unload?)
-            ->(klass) { Dependencies.to_unload?(klass.name) }
-          else
-            ->(klass) { Dependencies.autoloaded?(klass) }
-          end
-
           @@direct_descendants.each do |klass, descendants|
-            if to_unload[klass]
+            if Dependencies.autoloaded?(klass)
               @@direct_descendants.delete(klass)
             else
-              descendants.reject! { |v| to_unload[v] }
+              descendants.reject! { |v| Dependencies.autoloaded?(v) }
             end
           end
         else

railties/test/application/zeitwerk_integration_test.rb

@@ -98,35 +98,47 @@ class ZeitwerkIntegrationTest < ActiveSupport::TestCase
     assert_nil deps.safe_constantize("Admin")
   end
 
-  test "to_unload? says if a constant would be unloaded (main)" do
+  test "unloadable constants (main)" do
     app_file "app/models/user.rb", "class User; end"
     app_file "app/models/post.rb", "class Post; end"
     boot
 
     assert Post
-    assert deps.to_unload?("Post")
-    assert_not deps.to_unload?("User")
+
+    assert deps.autoloaded?("Post")
+    assert deps.autoloaded?(Post)
+    assert_not deps.autoloaded?("User")
+
+    assert_equal ["Post"], deps.autoloaded_constants
   end
 
-  test "to_unload? says if a constant would be unloaded (once)" do
+  test "unloadable constants (once)" do
     add_to_config 'config.autoload_once_paths << "#{Rails.root}/extras"'
     app_file "extras/foo.rb", "class Foo; end"
     app_file "extras/bar.rb", "class Bar; end"
     boot
 
     assert Foo
-    assert_not deps.to_unload?("Foo")
-    assert_not deps.to_unload?("Bar")
+
+    assert_not deps.autoloaded?("Foo")
+    assert_not deps.autoloaded?(Foo)
+    assert_not deps.autoloaded?("Bar")
+
+    assert_empty deps.autoloaded_constants
   end
 
-  test "to_unload? says if a constant would be unloaded (reloading disabled)" do
+  test "unloadable constants (reloading disabled)" do
     app_file "app/models/user.rb", "class User; end"
     app_file "app/models/post.rb", "class Post; end"
     boot("production")
 
     assert Post
-    assert_not deps.to_unload?("Post")
-    assert_not deps.to_unload?("User")
+
+    assert_not deps.autoloaded?("Post")
+    assert_not deps.autoloaded?(Post)
+    assert_not deps.autoloaded?("User")
+
+    assert_empty deps.autoloaded_constants
   end
 
   test "eager loading loads the application code" do
@@ -335,46 +347,4 @@ class ZeitwerkIntegrationTest < ActiveSupport::TestCase
       assert_nil autoloader.logger
     end
   end
-
-  # This is here because to guarantee classic mode works as always, Zeitwerk
-  # integration does not touch anything in classic. The descendants tracker is a
-  # very small one-liner exception. We leave its main test suite untouched, and
-  # add some minimal safety net here.
-  #
-  # When time passes, things are going to be reorganized (famous last words).
-  test "descendants tracker" do
-    class ::ZeitwerkDTIntegrationTestRoot
-      extend ActiveSupport::DescendantsTracker
-    end
-    class ::ZeitwerkDTIntegrationTestChild < ::ZeitwerkDTIntegrationTestRoot; end
-    class ::ZeitwerkDTIntegrationTestGrandchild < ::ZeitwerkDTIntegrationTestChild; end
-
-    begin
-      app_file "app/models/user.rb", "class User < ZeitwerkDTIntegrationTestRoot; end"
-      app_file "app/models/post.rb", "class Post < ZeitwerkDTIntegrationTestRoot; end"
-      app_file "app/models/tutorial.rb", "class Tutorial < Post; end"
-      boot
-
-      assert User
-      assert Tutorial
-
-      direct_descendants = [ZeitwerkDTIntegrationTestChild, User, Post].to_set
-      assert_equal direct_descendants, ZeitwerkDTIntegrationTestRoot.direct_descendants.to_set
-
-      descendants = direct_descendants.merge([ZeitwerkDTIntegrationTestGrandchild, Tutorial])
-      assert_equal descendants, ZeitwerkDTIntegrationTestRoot.descendants.to_set
-
-      ActiveSupport::DescendantsTracker.clear
-
-      direct_descendants = [ZeitwerkDTIntegrationTestChild].to_set
-      assert_equal direct_descendants, ZeitwerkDTIntegrationTestRoot.direct_descendants.to_set
-
-      descendants = direct_descendants.merge([ZeitwerkDTIntegrationTestGrandchild])
-      assert_equal descendants, ZeitwerkDTIntegrationTestRoot.descendants.to_set
-    ensure
-      Object.send(:remove_const, :ZeitwerkDTIntegrationTestRoot)
-      Object.send(:remove_const, :ZeitwerkDTIntegrationTestChild)
-      Object.send(:remove_const, :ZeitwerkDTIntegrationTestGrandchild)
-    end
-  end
 end