Initial working version with tests

.gitignore

@@ -7,3 +7,4 @@
 /spec/reports/
 /tmp/
 Gemfile.lock
+test/log/

Gemfile

@@ -10,3 +10,5 @@ gem "rake", "~> 13.0"
 gem "minitest", "~> 5.16"
 
 gem "standard", "~> 1.3"
+
+gem "rails"

lib/flickwerk.rb

@@ -1,8 +1,16 @@
 # frozen_string_literal: true
 
 require_relative "flickwerk/version"
+require "active_support/core_ext/module/attribute_accessors"
+require "flickwerk/railtie" if defined?(Rails)
 
 module Flickwerk
   class Error < StandardError; end
-  # Your code goes here...
+
+  mattr_accessor :patch_paths
+  self.patch_paths = []
+
+  def self.included(engine)
+    patch_paths << engine.root.join("app/patches")
+  end
 end

lib/flickwerk/patch_loader.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module Flickwerk
+  class PatchLoader
+    DECORATED_CLASS_PATTERN = /(?<decorated_class>[A-Z][a-zA-Z:]+)(\.prepend[\s(])/
+
+    attr_reader :path, :autoloader
+
+    def initialize(path, autoloader: Rails.autoloaders.main)
+      @path = path
+      @autoloader = autoloader
+    end
+
+    def call
+      path.glob("**/*_patch.rb") do |patch_path|
+        # Match all the classes that are prepended in the file
+        matches = File.read(patch_path).scan(DECORATED_CLASS_PATTERN).flatten
+
+        # Don't do a thing if there's no prepending.
+        next unless matches.present?
+
+        # For each unique match, make sure we load the decorator when the base class is loaded
+        matches.uniq.each do |decorated_class|
+          # Zeitwerk tells us which constant it expects a file to provide.
+          decorator_constant = autoloader.cpath_expected_at(patch_path)
+          # Sprinkle some debugging.
+          Rails.logger.debug("Preparing to autoload #{decorated_class} with #{decorator_constant}")
+          # If the class has not been loaded, we can add a hook to load the decorator when it is.
+          # Multiple hooks are no problem, as long as all decorators are namespaced appropriately.
+          autoloader.on_load(decorated_class) do |base|
+            Rails.logger.debug("Loading #{decorator_constant} in order to modify #{base}")
+            decorator_constant.constantize
+          end
+        end
+      end
+    end
+  end
+end

lib/flickwerk/railtie.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require "flickwerk/patch_loader"
+
+class Flickwerk::Railtie < Rails::Railtie
+  initializer "flickwerk.add_patches", after: :setup_main_autoloader do
+    Flickwerk.patch_paths.each do |path|
+      Flickwerk::PatchLoader.new(path).call
+    end
+  end
+end

test/dummy_app/app/models/concerns/user_methods.rb

@@ -0,0 +1,5 @@
+module UserMethods
+  def last_name
+    "Vader"
+  end
+end

test/dummy_app/app/models/user.rb

@@ -0,0 +1,5 @@
+class User
+  def name
+    "Darth"
+  end
+end

test/dummy_app/app/patches/page_patch.rb

@@ -0,0 +1,7 @@
+module PagePatch
+  def title
+    "Changed from Host app"
+  end
+
+  DummyCms::Page.prepend(self)
+end

test/dummy_app/app/patches/user_patch.rb

@@ -0,0 +1,11 @@
+module UserPatch
+  def self.prepended(base)
+    base.include(UserMethods)
+  end
+
+  def age
+    26
+  end
+
+  User.prepend(self)
+end

test/dummy_app/config/application.rb

@@ -0,0 +1,29 @@
+require "rails"
+require "flickwerk/railtie"
+
+module DummyApp
+  class Application < ::Rails::Application
+    config.root = File.expand_path("../", __dir__)
+    include Flickwerk
+    config.autoload_paths << File.expand_path("../app/models", __dir__)
+
+    config.load_defaults("#{Rails::VERSION::MAJOR}.#{Rails::VERSION::MINOR}")
+
+    # It needs to be explicitly set from Rails 7
+    # https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#upgrading-from-rails-6-1-to-rails-7-0-spring
+    config.cache_classes = true
+
+    config.active_support.deprecation = :stderr
+    config.log_level = :debug
+
+    # Improve test suite performance:
+    config.eager_load = false
+    config.cache_store = :memory_store
+
+    # We don't use a web server, so we let Rails serve assets.
+    config.public_file_server.enabled = true
+
+    # No need to use credentials file in a test environment.
+    config.secret_key_base = 'SECRET_TOKEN'
+  end
+end

test/dummy_app/log/development.log

@@ -0,0 +1,218 @@
+Preparing to autoload User with UserPatch
+Loading UserPatch in order to modify User
+Preparing to autoload User with UserPatch
+Loading UserPatch in order to modify User
+Preparing to autoload User with UserPatch
+Loading UserPatch in order to modify User
+Preparing to autoload User with UserPatch
+Loading UserPatch in order to modify User
+Preparing to autoload User with UserPatch
+Loading UserPatch in order to modify User
+Preparing to autoload User with UserPatch
+Loading UserPatch in order to modify User
+Preparing to autoload User with UserPatch
+Loading UserPatch in order to modify User
+Preparing to autoload User with UserPatch
+Loading UserPatch in order to modify User
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Loading UserPatch in order to modify User
+Preparing to autoload Blog::Post with BlogPostPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload Cms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Cms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Cms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading BlogPostPatch in order to modify Blog::Post
+Loading UserPatch in order to modify User
+Preparing to autoload Cms::Page with PagePatch
+Preparing to autoload Cms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Cms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Loading BlogPostPatch in order to modify Blog::Post
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Loading PostPatch in order to modify DummyBlog::Post
+Loading UserPatch in order to modify User
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with PostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading PostPatch in order to modify DummyBlog::Post
+Loading UserPatch in order to modify User
+Loading PostPatch in order to modify DummyBlog::Post
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload Blog::Post with BlogPostPatch
+Loading UserPatch in order to modify User
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Loading UserPatch in order to modify User
+Loading DummyBlogPostPatch in order to modify DummyBlog::Post
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Loading UserPatch in order to modify User
+Loading PagePatch in order to modify DummyCms::Page
+Loading DummyBlogPostPatch in order to modify DummyBlog::Post
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Loading UserPatch in order to modify User
+Loading PagePatch in order to modify DummyCms::Page
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Loading PagePatch in order to modify DummyCms::Page
+Loading UserPatch in order to modify User
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Loading UserPatch in order to modify User
+Loading DummyBlogPostPatch in order to modify DummyBlog::Post
+Loading PagePatch in order to modify DummyCms::Page
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Loading PagePatch in order to modify DummyCms::Page
+Loading UserPatch in order to modify User
+Loading DummyBlogPostPatch in order to modify DummyBlog::Post
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyCms::Page with PagePatch
+Preparing to autoload User with UserPatch
+Preparing to autoload DummyBlog::Post with DummyBlogPostPatch
+Loading UserPatch in order to modify User
+Loading PagePatch in order to modify DummyCms::Page
+Loading DummyBlogPostPatch in order to modify DummyBlog::Post

test/dummy_blog/app/models/dummy_blog/post.rb

@@ -0,0 +1,5 @@
+class DummyBlog::Post
+  def title
+    "Original title"
+  end
+end

test/dummy_blog/lib/dummy_blog.rb

@@ -0,0 +1 @@
+require "dummy_blog/engine"

test/dummy_blog/lib/dummy_blog/engine.rb

@@ -0,0 +1,5 @@
+require "flickwerk"
+
+class BlogEngine < Rails::Engine
+  include Flickwerk
+end

test/dummy_cms/app/models/dummy_cms/page.rb

@@ -0,0 +1,2 @@
+class DummyCms::Page
+end

test/dummy_cms/app/patches/dummy_blog_post_patch.rb

@@ -0,0 +1,7 @@
+module DummyBlogPostPatch
+  def title
+    "Edited from CMS"
+  end
+
+  DummyBlog::Post.prepend(self)
+end

test/dummy_cms/lib/dummy_cms.rb

@@ -0,0 +1,4 @@
+module DummyCms
+end
+
+require "dummy_cms/engine"

test/dummy_cms/lib/dummy_cms/engine.rb

@@ -0,0 +1,3 @@
+class DummyCms::Engine < Rails::Engine
+  include Flickwerk
+end