Add zeitwerk powered decorators support

Co-Authored-By: Andrea Longhi <[email protected]>

lib/solidus_support.rb

@@ -6,6 +6,8 @@
 require 'solidus_core'
 
 module SolidusSupport
+  autoload :Decorators, 'solidus_support/decorators'
+
   class << self
     def solidus_gem_version
       ActiveSupport::Deprecation.warn <<-WARN.squish, caller

lib/solidus_support/decorators.rb

@@ -0,0 +1,159 @@
+# SolidusSupport::Decorators is an efficient decorators loader that will extend the behavior of existing
+# classes and modules without eagerly loading all of your decorators at each request.
+#
+# It nicely falls back to reloading them all when zeitwerk is not available, but will only load the decorators for a
+# given base class when it can. This means that, on an average Solidus application, instead of loading 171 decorators
+# and 61 base classes with all their dependency it will just load the ones needed by the current request, or, if
+# starting a console, almost nothing.
+#
+# It will also prevent some nasty edge cases in which the use of `Rails.application.config.to_prepare(&…)` would do
+# some things twice, messing up calls to super inside decorators (`to_prepare` is actually called twice under some
+# circumstances).
+#
+# Migrating from Prependers:
+#
+#   require 'solidus_support/decorators'
+#   SolidusSupport::Decorators.autoload_decorators(Rails.root.join("app/prependers/**/*.rb"), autoprepend: true) do |path|
+#     relative = path.relative_path_from(Rails.root.join("app/prependers")) # models/spree/order/add_feature.rb
+#     parts = relative.to_s.split(File::SEPARATOR)
+#
+#     {
+#       # remove models/
+#       # => "AcmeCorp::Spree::Order::AddFeature"
+#       decorator: parts[1..-1].join("/").sub(/\.rb$/,'').camelize, # "AcmeCorp::Spree::Order::AddFeature"
+#
+#       # remove models/acme_corp/ and /add_feature.rb
+#       # => "Spree::Order"
+#       base: parts[2..-2].join("/").camelize, # "Spree::Order"
+#     }
+#   end
+#
+# Migrating from classic Solidus decorators
+#
+#   require 'solidus_support/decorators'
+#   SolidusDecorators.autoload_decorators("#{Rails.root}/app/**/*_decorator.rb") do |path|
+#     relative_path = path.relative_path_from(Rails.root.join("app/")) # models/acme_corp/order_decorator.rb
+#     parts = relative_path.to_s.split(File::SEPARATOR)
+#
+#     {
+#       # remove models/acme_corp/ and _decorator.rb, add spree/
+#       # => "Spree::Order"
+#       base: (["spree"] + parts[2..-1]).join("/").chomp("_decorator.rb").camelize,
+#
+#       # remove models/
+#       # => "AcmeCorp::Spree::Order::AddFeature"
+#       decorator: parts[1..-1].join("/").chomp(".rb").camelize,
+#     }
+#   end
+#
+# A more complex example with legacy mixed behaviors
+#
+#   require 'solidus_support/decorators'
+#   SolidusSupport::Decorators.autoload_decorators("#{Rails.root}/app/**/*_decorator.rb", autoprepend: false) do |path|
+#     case path.to_s
+#     when /lockable_decorator/
+#       nil # not a real decorator
+#     when /carton_decorator/
+#       {
+#         base: "Spree::Carton",
+#         decorator: "AcmeCorp::CartonDecorator",
+#       }
+#     when /devise_controller/
+#       {
+#         base: "DeviseController",
+#         decorator: "AcmeCorp::DeviseControllerDecorator",
+#       }
+#     when /inventory_unit_finalizer/
+#       {
+#         base: "Spree::Stock::InventoryUnitsFinalizer",
+#         decorator: "AcmeCorp::Stock::InventoryUnitFinalizerDecorator"
+#       }
+#     else
+#       relative_path = path.relative_path_from(Rails.root.join("app/")) # models/acme_corp/order_decorator.rb
+#       parts = relative_path.to_s.split(File::SEPARATOR)
+#
+#       {
+#         base: (["spree"] + parts[2..-1]).join("/").chomp("_decorator.rb").camelize, # => "Spree::Order"
+#         decorator: parts[1..-1].join("/").chomp(".rb").camelize, # => "AcmeCorp::OrderDecorator"
+#       }
+#     end
+#   end
+#
+module SolidusSupport::Decorators
+  extend self
+
+  def autoload_decorators(glob, autoprepend: false)
+    self.decorators_by_base = Hash.new { |h,k| h[k] = [] }
+    self.autoprepend = autoprepend
+
+    Dir[glob.to_s].map do |path|
+      puts "<<< #{path}"
+      result = yield(Pathname(path)) or next
+
+      base = result.fetch(:base)
+      decorator = result.fetch(:decorator)
+
+      decorators_by_base[base] << decorator
+    end
+
+    if Rails.application.config.respond_to?(:autoloader) && Rails.application.config.autoloader == :zeitwerk
+      setup_zeitwerk
+    else
+      setup_classic
+    end
+  end
+
+  private
+
+  attr_accessor :decorators_by_base, :autoprepend
+
+  def decorate_base(base, decorators)
+    puts "==> #{base} #{decorators.inspect}"
+    # puts caller
+    base_module = base.constantize
+
+    decorators.each do |decorator|
+      puts "--> #{decorator}"
+      decorator_module = decorator.constantize
+
+      if autoprepend
+        base_module.prepend decorator_module
+        if decorator_module.const_defined?(:ClassMethods)
+          base_module.singleton_class.prepend decorator_module::ClassMethods
+        end
+      end
+    end
+  end
+
+  def setup_classic
+    _self = self # to_prepare runs in the context of the app
+
+    Rails.application.config.to_prepare do
+      _self.instance_eval do
+        decorators_by_base.each do |base, decorators|
+          decorate_base(base, decorators)
+        end
+      end
+    end
+  end
+
+  def on_load_callback_installed
+    @on_load_callback_installed ||= {}
+  end
+
+  def setup_zeitwerk
+    loader = Rails.autoloaders.main
+
+    decorators_by_base.keys.each do |base|
+      next if on_load_callback_installed.key?(base)
+      on_load_callback_installed[base] = true
+      puts "==> on_load #{base}"
+
+      loader.on_load(base) do
+        # this needs to be dynamic because the call back is set up only
+        # once, and the number of decorators may change
+        decorate_base(base, decorators_by_base[base])
+      end
+    end
+  end
+end

lib/solidus_support/engine_extensions.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'solidus_support/decorators'
+
 module SolidusSupport
   module EngineExtensions
     include ActiveSupport::Deprecation::DeprecatedConstantAccessor
@@ -89,11 +91,19 @@ def enable_solidus_engine_support(engine)
 
         config.autoload_paths += path.glob('*')
 
-        engine_context = self
-        config.to_prepare do
-          engine_context.instance_eval do
-            load_solidus_decorators_from(path)
-          end
+        SolidusDecorators.autoload_decorators(path.glob('**/*.rb')) do |path|
+          relative_path = path.relative_path_from(Rails.root.join("app/")) # models/acme_corp/order_decorator.rb
+          parts = relative_path.to_s.split(File::SEPARATOR)
+
+          {
+            # remove models/acme_corp/ and _decorator.rb, add spree/
+            # => "Spree::Order"
+            base: (["spree"] + parts[2..-1]).join("/").chomp("_decorator.rb").camelize,
+
+            # remove models/
+            # => "AcmeCorp::Spree::Order::AddFeature"
+            decorator: parts[1..-1].join("/").chomp(".rb").camelize,
+          }
         end
       end
     end