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require 'rails/railtie'
require 'active_support/core_ext/module/delegation'
require 'pathname'
require 'rbconfig'
require 'rails/engine/railties'
module Rails
# <tt>Rails::Engine</tt> allows you to wrap a specific Rails application or subset of
# functionality and share it with other applications. Since Rails 3.0, every
# <tt>Rails::Application</tt> is just an engine, which allows for simple
# feature and application sharing.
#
# Any <tt>Rails::Engine</tt> is also a <tt>Rails::Railtie</tt>, so the same
# methods (like <tt>rake_tasks</tt> and +generators+) and configuration
# options that are available in railties can also be used in engines.
#
# == Creating an Engine
#
# In Rails versions prior to 3.0, your gems automatically behaved as engines, however,
# this coupled Rails to Rubygems. Since Rails 3.0, if you want a gem to automatically
# behave as an engine, you have to specify an +Engine+ for it somewhere inside
# your plugin's +lib+ folder (similar to how we specify a +Railtie+):
#
# # lib/my_engine.rb
# module MyEngine
# class Engine < Rails::Engine
# end
# end
#
# Then ensure that this file is loaded at the top of your <tt>config/application.rb</tt>
# (or in your +Gemfile+) and it will automatically load models, controllers and helpers
# inside +app+, load routes at <tt>config/routes.rb</tt>, load locales at
# <tt>config/locales/*</tt>, and load tasks at <tt>lib/tasks/*</tt>.
#
# == Configuration
#
# Besides the +Railtie+ configuration which is shared across the application, in a
# <tt>Rails::Engine</tt> you can access <tt>autoload_paths</tt>, <tt>eager_load_paths</tt>
# and <tt>autoload_once_paths</tt>, which, differently from a <tt>Railtie</tt>, are scoped to
# the current engine.
#
# Example:
#
# class MyEngine < Rails::Engine
# # Add a load path for this specific Engine
# config.autoload_paths << File.expand_path("../lib/some/path", __FILE__)
#
# initializer "my_engine.add_middleware" do |app|
# app.middleware.use MyEngine::Middleware
# end
# end
#
# == Generators
#
# You can set up generators for engines with <tt>config.generators</tt> method:
#
# class MyEngine < Rails::Engine
# config.generators do |g|
# g.orm :active_record
# g.template_engine :erb
# g.test_framework :test_unit
# end
# end
#
# You can also set generators for an application by using <tt>config.app_generators</tt>:
#
# class MyEngine < Rails::Engine
# # note that you can also pass block to app_generators in the same way you
# # can pass it to generators method
# config.app_generators.orm :datamapper
# end
#
# == Paths
#
# Since Rails 3.0, applications and engines have more flexible path configuration (as
# opposed to the previous hardcoded path configuration). This means that you are not
# required to place your controllers at <tt>app/controllers</tt>, but in any place
# which you find convenient.
#
# For example, let's suppose you want to place your controllers in <tt>lib/controllers</tt>.
# You can set that as an option:
#
# class MyEngine < Rails::Engine
# paths["app/controllers"] = "lib/controllers"
# end
#
# You can also have your controllers loaded from both <tt>app/controllers</tt> and
# <tt>lib/controllers</tt>:
#
# class MyEngine < Rails::Engine
# paths["app/controllers"] << "lib/controllers"
# end
#
# The available paths in an engine are:
#
# class MyEngine < Rails::Engine
# paths["app"] # => ["app"]
# paths["app/controllers"] # => ["app/controllers"]
# paths["app/helpers"] # => ["app/helpers"]
# paths["app/models"] # => ["app/models"]
# paths["app/views"] # => ["app/views"]
# paths["lib"] # => ["lib"]
# paths["lib/tasks"] # => ["lib/tasks"]
# paths["config"] # => ["config"]
# paths["config/initializers"] # => ["config/initializers"]
# paths["config/locales"] # => ["config/locales"]
# paths["config/routes"] # => ["config/routes.rb"]
# end
#
# The <tt>Application</tt> class adds a couple more paths to this set. And as in your
# <tt>Application</tt>, all folders under +app+ are automatically added to the load path.
# If you have an <tt>app/observers</tt> folder for example, it will be added by default.
#
# == Endpoint
#
# An engine can be also a rack application. It can be useful if you have a rack application that
# you would like to wrap with +Engine+ and provide some of the +Engine+'s features.
#
# To do that, use the +endpoint+ method:
#
# module MyEngine
# class Engine < Rails::Engine
# endpoint MyRackApplication
# end
# end
#
# Now you can mount your engine in application's routes just like that:
#
# MyRailsApp::Application.routes.draw do
# mount MyEngine::Engine => "/engine"
# end
#
# == Middleware stack
#
# As an engine can now be a rack endpoint, it can also have a middleware
# stack. The usage is exactly the same as in <tt>Application</tt>:
#
# module MyEngine
# class Engine < Rails::Engine
# middleware.use SomeMiddleware
# end
# end
#
# == Routes
#
# If you don't specify an endpoint, routes will be used as the default
# endpoint. You can use them just like you use an application's routes:
#
# # ENGINE/config/routes.rb
# MyEngine::Engine.routes.draw do
# match "/" => "posts#index"
# end
#
# == Mount priority
#
# Note that now there can be more than one router in your application, and it's better to avoid
# passing requests through many routers. Consider this situation:
#
# MyRailsApp::Application.routes.draw do
# mount MyEngine::Engine => "/blog"
# match "/blog/omg" => "main#omg"
# end
#
# +MyEngine+ is mounted at <tt>/blog</tt>, and <tt>/blog/omg</tt> points to application's
# controller. In such a situation, requests to <tt>/blog/omg</tt> will go through +MyEngine+,
# and if there is no such route in +Engine+'s routes, it will be dispatched to <tt>main#omg</tt>.
# It's much better to swap that:
#
# MyRailsApp::Application.routes.draw do
# match "/blog/omg" => "main#omg"
# mount MyEngine::Engine => "/blog"
# end
#
# Now, +Engine+ will get only requests that were not handled by +Application+.
#
# == Engine name
#
# There are some places where an Engine's name is used:
#
# * routes: when you mount an Engine with <tt>mount(MyEngine::Engine => '/my_engine')</tt>,
# it's used as default :as option
# * some of the rake tasks are based on engine name, e.g. <tt>my_engine:install:migrations</tt>,
# <tt>my_engine:install:assets</tt>
#
# Engine name is set by default based on class name. For <tt>MyEngine::Engine</tt> it will be
# <tt>my_engine_engine</tt>. You can change it manually using the <tt>engine_name</tt> method:
#
# module MyEngine
# class Engine < Rails::Engine
# engine_name "my_engine"
# end
# end
#
# == Isolated Engine
#
# Normally when you create controllers, helpers and models inside an engine, they are treated
# as if they were created inside the application itself. This means that all helpers and
# named routes from the application will be available to your engine's controllers as well.
#
# However, sometimes you want to isolate your engine from the application, especially if your engine
# has its own router. To do that, you simply need to call +isolate_namespace+. This method requires
# you to pass a module where all your controllers, helpers and models should be nested to:
#
# module MyEngine
# class Engine < Rails::Engine
# isolate_namespace MyEngine
# end
# end
#
# With such an engine, everything that is inside the +MyEngine+ module will be isolated from
# the application.
#
# Consider such controller:
#
# module MyEngine
# class FooController < ActionController::Base
# end
# end
#
# If an engine is marked as isolated, +FooController+ has access only to helpers from +Engine+ and
# <tt>url_helpers</tt> from <tt>MyEngine::Engine.routes</tt>.
#
# The next thing that changes in isolated engines is the behavior of routes. Normally, when you namespace
# your controllers, you also need to do namespace all your routes. With an isolated engine,
# the namespace is applied by default, so you can ignore it in routes:
#
# MyEngine::Engine.routes.draw do
# resources :articles
# end
#
# The routes above will automatically point to <tt>MyEngine::ApplicationController</tt>. Furthermore, you don't
# need to use longer url helpers like <tt>my_engine_articles_path</tt>. Instead, you should simply use
# <tt>articles_path</tt> as you would do with your application.
#
# To make that behavior consistent with other parts of the framework, an isolated engine also has influence on
# <tt>ActiveModel::Naming</tt>. When you use a namespaced model, like <tt>MyEngine::Article</tt>, it will normally
# use the prefix "my_engine". In an isolated engine, the prefix will be omitted in url helpers and
# form fields for convenience.
#
# polymorphic_url(MyEngine::Article.new) # => "articles_path"
#
# form_for(MyEngine::Article.new) do
# text_field :title # => <input type="text" name="article[title]" id="article_title" />
# end
#
# Additionally, an isolated engine will set its name according to namespace, so
# MyEngine::Engine.engine_name will be "my_engine". It will also set MyEngine.table_name_prefix
# to "my_engine_", changing the MyEngine::Article model to use the my_engine_article table.
#
# == Using Engine's routes outside Engine
#
# Since you can now mount an engine inside application's routes, you do not have direct access to +Engine+'s
# <tt>url_helpers</tt> inside +Application+. When you mount an engine in an application's routes, a special helper is
# created to allow you to do that. Consider such a scenario:
#
# # config/routes.rb
# MyApplication::Application.routes.draw do
# mount MyEngine::Engine => "/my_engine", :as => "my_engine"
# match "/foo" => "foo#index"
# end
#
# Now, you can use the <tt>my_engine</tt> helper inside your application:
#
# class FooController < ApplicationController
# def index
# my_engine.root_url #=> /my_engine/
# end
# end
#
# There is also a <tt>main_app</tt> helper that gives you access to application's routes inside Engine:
#
# module MyEngine
# class BarController
# def index
# main_app.foo_path #=> /foo
# end
# end
# end
#
# Note that the <tt>:as</tt> option given to mount takes the <tt>engine_name</tt> as default, so most of the time
# you can simply omit it.
#
# Finally, if you want to generate a url to an engine's route using
# <tt>polymorphic_url</tt>, you also need to pass the engine helper. Let's
# say that you want to create a form pointing to one of the engine's routes.
# All you need to do is pass the helper as the first element in array with
# attributes for url:
#
# form_for([my_engine, @user])
#
# This code will use <tt>my_engine.user_path(@user)</tt> to generate the proper route.
#
# == Isolated engine's helpers
#
# Sometimes you may want to isolate engine, but use helpers that are defined for it.
# If you want to share just a few specific helpers you can add them to application's
# helpers in ApplicationController:
#
# class ApplicationController < ActionController::Base
# helper MyEngine::SharedEngineHelper
# end
#
# If you want to include all of the engine's helpers, you can use #helpers method on an engine's
# instance:
#
# class ApplicationController < ActionController::Base
# helper MyEngine::Engine.helpers
# end
#
# It will include all of the helpers from engine's directory. Take into account that this does
# not include helpers defined in controllers with helper_method or other similar solutions,
# only helpers defined in the helpers directory will be included.
#
# == Migrations & seed data
#
# Engines can have their own migrations. The default path for migrations is exactly the same
# as in application: <tt>db/migrate</tt>
#
# To use engine's migrations in application you can use rake task, which copies them to
# application's dir:
#
# rake ENGINE_NAME:install:migrations
#
# Note that some of the migrations may be skipped if a migration with the same name already exists
# in application. In such a situation you must decide whether to leave that migration or rename the
# migration in the application and rerun copying migrations.
#
# If your engine has migrations, you may also want to prepare data for the database in
# the <tt>seeds.rb</tt> file. You can load that data using the <tt>load_seed</tt> method, e.g.
#
# MyEngine::Engine.load_seed
#
# == Loading priority
#
# In order to change engine's priority you can use config.railties_order in main application.
# It will affect the priority of loading views, helpers, assets and all the other files
# related to engine or application.
#
# Example:
#
# # load Blog::Engine with highest priority, followed by application and other railties
# config.railties_order = [Blog::Engine, :main_app, :all]
#
class Engine < Railtie
autoload :Configuration, "rails/engine/configuration"
autoload :Railties, "rails/engine/railties"
def load_generators(app=self)
initialize_generators
railties.all { |r| r.load_generators(app) }
Rails::Generators.configure!(app.config.generators)
super
self
end
class << self
attr_accessor :called_from, :isolated
alias :isolated? :isolated
alias :engine_name :railtie_name
def inherited(base)
unless base.abstract_railtie?
base.called_from = begin
# Remove the line number from backtraces making sure we don't leave anything behind
call_stack = caller.map { |p| p.sub(/:\d+.*/, '') }
File.dirname(call_stack.detect { |p| p !~ %r[railties[\w.-]*/lib/rails|rack[\w.-]*/lib/rack] })
end
end
super
end
def endpoint(endpoint = nil)
@endpoint ||= nil
@endpoint = endpoint if endpoint
@endpoint
end
def isolate_namespace(mod)
engine_name(generate_railtie_name(mod))
self.routes.default_scope = { :module => ActiveSupport::Inflector.underscore(mod.name) }
self.isolated = true
unless mod.respond_to?(:railtie_namespace)
name, railtie = engine_name, self
mod.singleton_class.instance_eval do
define_method(:railtie_namespace) { railtie }
unless mod.respond_to?(:table_name_prefix)
define_method(:table_name_prefix) { "#{name}_" }
end
unless mod.respond_to?(:use_relative_model_naming?)
class_eval "def use_relative_model_naming?; true; end", __FILE__, __LINE__
end
unless mod.respond_to?(:railtie_helpers_paths)
define_method(:railtie_helpers_paths) { railtie.helpers_paths }
end
unless mod.respond_to?(:railtie_routes_url_helpers)
define_method(:railtie_routes_url_helpers) { railtie.routes_url_helpers }
end
end
end
end
# Finds engine with given path
def find(path)
expanded_path = File.expand_path path.to_s
Rails::Engine::Railties.engines.find { |engine|
File.expand_path(engine.root.to_s) == expanded_path
}
end
end
delegate :middleware, :root, :paths, :to => :config
delegate :engine_name, :isolated?, :to => "self.class"
def load_tasks(app=self)
railties.all { |r| r.load_tasks(app) }
super
paths["lib/tasks"].existent.sort.each { |ext| load(ext) }
end
def load_console(app=self)
railties.all { |r| r.load_console(app) }
super
end
def eager_load!
railties.all(&:eager_load!)
config.eager_load_paths.each do |load_path|
matcher = /\A#{Regexp.escape(load_path)}\/(.*)\.rb\Z/
Dir.glob("#{load_path}/**/*.rb").sort.each do |file|
require_dependency file.sub(matcher, '\1')
end
end
end
def railties
@railties ||= self.class::Railties.new(config)
end
def helpers
@helpers ||= begin
helpers = Module.new
all = ActionController::Base.all_helpers_from_path(helpers_paths)
ActionController::Base.modules_for_helpers(all).each do |mod|
helpers.send(:include, mod)
end
helpers
end
end
def helpers_paths
paths["app/helpers"].existent
end
def routes_url_helpers
routes.url_helpers
end
def app
@app ||= begin
config.middleware = config.middleware.merge_into(default_middleware_stack)
config.middleware.build(endpoint)
end
end
def endpoint
self.class.endpoint || routes
end
def call(env)
app.call(env.merge!(env_config))
end
def env_config
@env_config ||= {
'action_dispatch.routes' => routes
}
end
def routes
@routes ||= ActionDispatch::Routing::RouteSet.new
@routes.append(&Proc.new) if block_given?
@routes
end
def ordered_railties
railties.all + [self]
end
def initializers
initializers = []
ordered_railties.each do |r|
if r == self
initializers += super
else
initializers += r.initializers
end
end
initializers
end
def config
@config ||= Engine::Configuration.new(find_root_with_flag("lib"))
end
# Load data from db/seeds.rb file. It can be used in to load engines'
# seeds, e.g.:
#
# Blog::Engine.load_seed
def load_seed
seed_file = paths["db/seeds"].existent.first
load(seed_file) if seed_file
end
# Add configured load paths to ruby load paths and remove duplicates.
initializer :set_load_path, :before => :bootstrap_hook do
_all_load_paths.reverse_each do |path|
$LOAD_PATH.unshift(path) if File.directory?(path)
end
$LOAD_PATH.uniq!
end
# Set the paths from which Rails will automatically load source files,
# and the load_once paths.
#
# This needs to be an initializer, since it needs to run once
# per engine and get the engine as a block parameter
initializer :set_autoload_paths, :before => :bootstrap_hook do |app|
ActiveSupport::Dependencies.autoload_paths.unshift(*_all_autoload_paths)
ActiveSupport::Dependencies.autoload_once_paths.unshift(*_all_autoload_once_paths)
# Freeze so future modifications will fail rather than do nothing mysteriously
config.autoload_paths.freeze
config.eager_load_paths.freeze
config.autoload_once_paths.freeze
end
initializer :add_routing_paths do |app|
paths = self.paths["config/routes"].existent
if routes? || paths.any?
app.routes_reloader.paths.unshift(*paths)
app.routes_reloader.route_sets << routes
end
end
# I18n load paths are a special case since the ones added
# later have higher priority.
initializer :add_locales do
config.i18n.railties_load_path.concat(paths["config/locales"].existent)
end
initializer :add_view_paths do
views = paths["app/views"].existent
unless views.empty?
ActiveSupport.on_load(:action_controller){ prepend_view_path(views) }
ActiveSupport.on_load(:action_mailer){ prepend_view_path(views) }
end
end
initializer :load_environment_config, :before => :load_environment_hook, :group => :all do
environment = paths["config/environments"].existent.first
require environment if environment
end
initializer :append_assets_path, :group => :all do |app|
app.config.assets.paths.unshift(*paths["vendor/assets"].existent_directories)
app.config.assets.paths.unshift(*paths["lib/assets"].existent_directories)
app.config.assets.paths.unshift(*paths["app/assets"].existent_directories)
end
initializer :prepend_helpers_path do |app|
if !isolated? || (app == self)
app.config.helpers_paths.unshift(*paths["app/helpers"].existent)
end
end
initializer :load_config_initializers do
config.paths["config/initializers"].existent.sort.each do |initializer|
load(initializer)
end
end
initializer :engines_blank_point do
# We need this initializer so all extra initializers added in engines are
# consistently executed after all the initializers above across all engines.
end
rake_tasks do
next if self.is_a?(Rails::Application)
next unless has_migrations?
namespace railtie_name do
namespace :install do
desc "Copy migrations from #{railtie_name} to application"
task :migrations do
ENV["FROM"] = railtie_name
Rake::Task["railties:install:migrations"].invoke
end
end
end
end
protected
def initialize_generators
require "rails/generators"
end
def routes?
defined?(@routes)
end
def has_migrations?
paths["db/migrate"].existent.any?
end
def find_root_with_flag(flag, default=nil)
root_path = self.class.called_from
while root_path && File.directory?(root_path) && !File.exist?("#{root_path}/#{flag}")
parent = File.dirname(root_path)
root_path = parent != root_path && parent
end
root = File.exist?("#{root_path}/#{flag}") ? root_path : default
raise "Could not find root path for #{self}" unless root
RbConfig::CONFIG['host_os'] =~ /mswin|mingw/ ?
Pathname.new(root).expand_path : Pathname.new(root).realpath
end
def default_middleware_stack
ActionDispatch::MiddlewareStack.new
end
def _all_autoload_once_paths
config.autoload_once_paths
end
def _all_autoload_paths
@_all_autoload_paths ||= (config.autoload_paths + config.eager_load_paths + config.autoload_once_paths).uniq
end
def _all_load_paths
@_all_load_paths ||= (config.paths.load_paths + _all_autoload_paths).uniq
end
end
end
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