Make zeitwerk work with autoextend

fixes FOO-2517

Change-Id: I510e4640d9ad0db9fd5f5db65611adcc8b60ef58
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/277075
Tested-by: Service Cloud Jenkins <[email protected]>
Reviewed-by: Ethan Vizitei <[email protected]>
QA-Review: Jacob Burroughs <[email protected]>
Product-Review: Jacob Burroughs <[email protected]>

gems/autoextend/autoextend.gemspec

@@ -18,5 +18,6 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "activesupport"
   spec.add_development_dependency "byebug"
+  spec.add_development_dependency "railties"
   spec.add_development_dependency "rspec", "~> 3.5.0"
 end

gems/autoextend/lib/autoextend.rb

@@ -18,20 +18,34 @@
 # with this program. If not, see <http://www.gnu.org/licenses/>.
 
 require_relative 'autoextend/extension'
+require_relative "autoextend/railtie" if defined?(Rails::Railtie)
 
 module Autoextend
   class << self
-    def const_added(const, source:)
+    def const_added(const, source:, recursive: false)
       const_name = const.is_a?(String) ? const : const.name
       return [] unless const_name
 
       extensions_list = extensions_hash.fetch(const_name.to_sym, [])
-      sorted_extensions(extensions_list).each do |extension|
+      ret = sorted_extensions(extensions_list).each do |extension|
         if const == const_name
           const = Object.const_get(const_name, false)
         end
         extension.extend(const, source: source)
       end
+
+      if recursive
+        const.constants(false).each do |child|
+          next if const.autoload?(child)
+
+          child_const = const.const_get(child, false)
+          next unless child_const.is_a?(Module)
+
+          const_added(child_const, source: source, recursive: true)
+        end
+      end
+
+      ret
     end
 
     # Add a hook to automatically extend a class or module with a module,
@@ -94,7 +108,13 @@ def hook(const_name,
       end
 
       # immediately extend the class if it's already defined
-      if Object.const_defined?(const_name.to_s, false)
+      # If autoload? is true, don't use const_defined? as it is set up to be autoloaded but hasn't been loaded yet
+      module_chain = const_name.to_s.split('::').inject([]) { |all, val| all + [[(all.last ? "#{all.last.first}::#{all.last[1]}" : nil), val]] }
+      exists_and_not_to_autoload = module_chain.all? do |mod, name|
+        mod = mod.nil? ? Object : Object.const_get(mod)
+        !mod.autoload?(name) && mod.const_defined?(name.to_s, false)
+      end
+      if exists_and_not_to_autoload
         extension.before.each do |before_module|
           if const_extensions.any? { |ext| ext.module_name == before_module }
             raise "Already included #{before_module}; cannot include #{module_name} first"
@@ -114,6 +134,20 @@ def extensions
       extensions_hash.values.flatten
     end
 
+    def inject_into_zetwerk
+      return unless Object.const_defined?(:Zeitwerk)
+
+      Zeitwerk::Registry.loaders.each do |loader|
+        loader.on_load do |_cpath, value, abspath|
+          # Skip autovivified modules from directories
+          next unless abspath.end_with?('.rb')
+          next unless value.is_a?(Module)
+
+          Autoextend.const_added(value, source: :Zeitwerk, recursive: true)
+        end
+      end
+    end
+
     private
 
     def sorted_extensions(extensions_list)
@@ -174,23 +208,12 @@ def included(klass)
 
 module Autoextend::ActiveSupport
   module Dependencies
-    def notify_autoextend_of_new_constant(constant)
-      Autoextend.const_added(constant, source: :'ActiveSupport::Dependencies')
-      # check for nested constants
-      constant.constants(false).each do |child|
-        child_const = constant.const_get(child, false)
-        next unless child_const.is_a?(Module)
-
-        notify_autoextend_of_new_constant(child_const)
-      end
-    end
-
     def new_constants_in(*_descs)
       super.each do |constant_name|
         constant = Object.const_get(constant_name, false)
         next unless constant.is_a?(Module)
 
-        notify_autoextend_of_new_constant(constant)
+        Autoextend.const_added(constant, source: :'ActiveSupport::Dependencies', recursive: true)
       end
     end
 

gems/autoextend/lib/autoextend/railtie.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+#
+# Copyright (C) 2021 - present Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+
+module Autoextend
+  class Railtie < Rails::Railtie
+    # CANVAS_RAILS6_1 this method will need changing for a post-rails 6.1 world
+    initializer "inject autoextend hooks" do
+      ::Autoextend.inject_into_zetwerk
+    end
+  end
+end

gems/autoextend/spec/autoextend_spec.rb

@@ -22,11 +22,30 @@
 # this is a weird thing we have to do to avoid a weird circular
 # require problem
 _x = ActiveSupport::Deprecation
-ActiveSupport::Dependencies.autoload_paths << File.expand_path("..", __FILE__)
+ActiveSupport::Dependencies.autoload_paths << File.expand_path("../autoload", __FILE__)
 ActiveSupport::Dependencies.hook!
 
 require 'autoextend'
 
+# CANVAS_RAILS6_1 this pattern will need reworking in a rails >= 7.0 world
+if ENV['WITH_ZEITWERK']
+  require 'zeitwerk'
+  require 'rails'
+  Rails.application = Class.new do
+    def self.config
+      Class.new do
+        def self.autoloader
+          :zeitwerk
+        end
+      end
+    end
+  end
+  require "active_support/dependencies/zeitwerk_integration"
+  ActiveSupport::Dependencies::ZeitwerkIntegration.take_over(enable_reloading: true)
+  # In an actual rails app this is handled by an initializer through railties
+  Autoextend.inject_into_zetwerk
+end
+
 describe Autoextend do
   before do
     module AutoextendSpec
@@ -55,6 +74,16 @@ def self.prepended(klass)
           PrependHelper.register_prepend(klass, 3)
         end
       end
+
+      module PrependExistingMethod
+        def self.prepended(klass)
+          klass.a_method
+        end
+
+        def b_method
+          true
+        end
+      end
     end
   end
 
@@ -176,12 +205,26 @@ module AutoextendSpec::MyExtension; end
       Autoextend.hook(:"AutoextendSpec::TestModule::Nested") do
         hooked += 1
       end
-      expect(defined?(AutoextendSpec::TestModule)).to equal(nil)
+      if ENV['WITH_ZEITWERK']
+        expect(AutoextendSpec.autoload?(:TestModule)).not_to be_nil
+      else
+        expect(defined?(AutoextendSpec::TestModule)).to be_nil
+      end
       expect(hooked).to equal(0)
       _x = AutoextendSpec::TestModule
       # this could have only been detected by Rails' autoloading
-      expect(defined?(AutoextendSpec::TestModule)).to eq('constant')
+      if ENV['WITH_ZEITWERK']
+        expect(AutoextendSpec.autoload?(:TestModule)).to be_nil
+      else
+        expect(defined?(AutoextendSpec::TestModule)).to eq('constant')
+      end
       expect(hooked).to equal(2)
     end
+
+    it "hooks an autoloaded module after_load" do
+      # This method will call an existing method on load
+      Autoextend.hook(:"AutoextendSpec::TestLaterMethod", :"AutoextendSpec::PrependExistingMethod", method: :prepend, after_load: true)
+      expect(AutoextendSpec::TestLaterMethod.new.b_method).to eq(true)
+    end
   end
 end

gems/autoextend/spec/autoload/autoextend_spec/test_later_method.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+#
+# Copyright (C) 2016 - present Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+
+class AutoextendSpec::TestLaterMethod
+  def self.a_method
+    true
+  end
+end

gems/autoextend/test.sh

@@ -3,3 +3,4 @@ set -e
 
 bundle check || bundle install
 bundle exec rspec spec
+WITH_ZEITWERK=true bundle exec rspec spec