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require 'rails/railtie'
require 'active_support/core_ext/module/delegation'
require 'pathname'
require 'rbconfig'
require 'rails/engine/railties'
module Rails
# Rails::Engine allows you to wrap a specific Rails application and share it accross
# different applications. Since Rails 3.0, every Rails::Application is nothing
# more than an Engine, allowing you to share it very easily.
#
# Any Rails::Engine is also a Rails::Railtie, so the same methods (like rake_tasks and
# generators) and configuration available in the latter can also be used in the former.
#
# == Creating an Engine
#
# In Rails versions before to 3.0, your gems automatically behaved as Engine, however
# this coupled Rails to Rubygems. Since Rails 3.0, if you want a gem to automatically
# behave as Engine, you have to specify an Engine for it somewhere inside your plugin
# lib folder (similar with how we spceify 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 config/application.rb (or in
# your Gemfile) and it will automatically load models, controllers and helpers
# inside app, load routes at "config/routes.rb", load locales at "config/locales/*",
# load tasks at "lib/tasks/*".
#
# == Configuration
#
# Besides the Railtie configuration which is shared across the application, in a
# Rails::Engine you can access autoload_paths, eager_load_paths and autoload_once_paths,
# which differently from a Railtie, 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
#
# == Paths
#
# Since Rails 3.0, both your Application and Engines do not have hardcoded paths.
# This means that you are not required to place your controllers at "app/controllers",
# but in any place which you find convenient.
#
# For example, let's suppose you want to lay your controllers at lib/controllers, all
# you need to do is:
#
# class MyEngine < Rails::Engine
# paths.app.controllers = "lib/controllers"
# end
#
# You can also have your controllers being loaded from both "app/controllers" and
# "lib/controllers":
#
# 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
#
# Your Application class adds a couple more paths to this set. And as in your Application,
# all folders under "app" are automatically added to the load path. So if you have
# "app/observers", it's added by default.
#
# == Endpoint
#
# 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 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 Engine can now be rack endpoint, it can also have a middleware stack. The usage is exactly
# the same as in application:
#
# module MyEngine
# class Engine < Rails::Engine
# middleware.use SomeMiddleware
# end
# end
#
# == Routes
#
# If you don't specify endpoint, routes will be used as default endpoint. You can use them
# just like you use 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 you application and it's better to avoid
# passing requests through many routers. Consider such situation:
#
# MyRailsApp::Application.routes.draw do
# mount MyEngine::Engine => "/blog"
# match "/blog/omg" => "main#omg"
# end
#
# MyEngine is mounted at "/blog" path and additionaly "/blog/omg" points application's controller.
# In such situation request to "/blog/omg" will go through MyEngine and if there is no such route
# in Engine's routes, it will be dispatched to "main#omg". 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.
#
# == Asset path
#
# When you use engine with its own public directory, you will probably want to copy or symlink it
# to application's public directory. To simplify generating paths for assets, you can set asset_path
# for an Engine:
#
# module MyEngine
# class Engine < Rails::Engine
# config.asset_path = "/my_engine/%s"
# end
# end
#
# With such config, asset paths will be automatically modified inside Engine:
# image_path("foo.jpg") #=> "/my_engine/images/foo.jpg"
#
# == Engine name
#
# There are some places where engine's name is used.
# * routes: when you mount engine with mount(MyEngine::Engine => '/my_engine'), it's used as default :as option
# * migrations: when you copy engine's migrations, they will be decorated with suffix based on engine_name, for example:
# 2010010203121314_create_users.my_engine.rb
#
# Engine name is set by default based on class name. For MyEngine::Engine it will be my_engine_engine.
# You can change it manually it manually using engine_name method:
#
# module MyEngine
# class Engine < Rails::Engine
# engine_name "my_engine"
# end
# end
#
# == Namespaced Engine
#
# Normally, when you create controllers, helpers and models inside engine, they are treated
# as they would be created inside application. One of the cosequences of that is including
# application's helpers and url_helpers inside controller. Sometimes, especially when your
# engine provides its own routes, you don't want that. To isolate engine's stuff from application
# you can use namespace method:
#
# module MyEngine
# class Engine < Rails::Engine
# namespace MyEngine
# end
# end
#
# With such Engine, everything that is inside MyEngine module, will be isolated from application.
#
# Consider such controller:
#
# module MyEngine
# class FooController < ActionController::Base
# end
# end
#
# If engine is marked as namespaced, FooController has access only to helpers from engine and
# url_helpers from MyEngine::Engine.routes.
#
# Additionaly namespaced engine will set its name according to namespace, so in that case:
# MyEngine::Engine.engine_name #=> "my_engine"
# and it will set MyEngine.table_name_prefix to "my_engine_"
#
# == Using Engine's routes outside Engine
#
# Since you can mount engine inside application's routes now, you do not have direct access to engine's
# url_helpers inside application. When you mount Engine in application's routes special helper is
# created to allow doing that. Consider such scenario:
#
# # APP/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 my_engine helper:
#
# class FooController < ApplicationController
# def index
# my_engine.root_url #=> /my_engine/
# end
# end
#
# There is also 'app' helper that gives you access to application's routes inside Engine:
#
# module MyEngine
# class BarController
# app.foo_path #=> /foo
# end
# end
#
# Note that :as option takes engine_name as default, so most of the time you can ommit it.
#
# If you want to generate url to engine's route using polymorphic_url, you can also use that helpers.
#
# Let's say that you want to create a form pointing to one of the engine's routes. All you need to do
# is passing helper as the first element in array with attributes for url:
#
# form_for([my_engine, @user])
#
# This code will use my_engine.user_path(@user) to generate proper route.
#
class Engine < Railtie
autoload :Configurable, "rails/engine/configurable"
autoload :Configuration, "rails/engine/configuration"
class << self
attr_accessor :called_from, :namespaced
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.split(':')[0..-2].join(':') }
File.dirname(call_stack.detect { |p| p !~ %r[railties[\w\-\.]*/lib/rails|rack[\w\-\.]*/lib/rack] })
end
end
super
end
def find_root_with_flag(flag, default=nil)
root_path = self.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 endpoint(endpoint = nil)
@endpoint = endpoint if endpoint
@endpoint
end
def namespace(mod)
# TODO: extract that into a module
engine_name(generate_railtie_name(mod))
_railtie = self
name = engine_name
mod.singleton_class.instance_eval do
define_method(:_railtie) do
_railtie
end
define_method(:table_name_prefix) do
"#{name}_"
end
end
self.routes.default_scope = {:module => name}
self.namespaced = true
end
def namespaced?
!!namespaced
end
end
delegate :middleware, :root, :paths, :to => :config
delegate :engine_name, :namespaced?, :to => "self.class"
def load_tasks
super
config.paths.lib.tasks.to_a.sort.each { |ext| load(ext) }
end
def 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 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,
'action_dispatch.asset_path' => config.asset_path
}
end
def routes
@routes ||= ActionDispatch::Routing::RouteSet.new
end
def initializers
initializers = []
railties.all { |r| initializers += r.initializers }
initializers += super
initializers
end
def config
@config ||= Engine::Configuration.new(find_root_with_flag("lib"))
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(*config.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.config.routes.to_a.each do |route|
app.routes_reloader.paths.unshift(route) if File.exists?(route)
end
end
# DEPRECATED: Remove in 3.1
initializer :add_routing_namespaces do |app|
paths.app.controllers.to_a.each do |load_path|
load_path = File.expand_path(load_path)
Dir["#{load_path}/*/**/*_controller.rb"].collect do |path|
namespace = File.dirname(path).sub(/#{Regexp.escape(load_path)}\/?/, '')
app.routes.controller_namespaces << namespace unless namespace.empty?
end
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.to_a)
end
initializer :add_view_paths do
views = paths.app.views.to_a
ActiveSupport.on_load(:action_controller) do
prepend_view_path(views)
end
ActiveSupport.on_load(:action_mailer) do
prepend_view_path(views)
end
end
initializer :load_environment_config, :before => :load_environment_hook do
environment = config.paths.config.environments.to_a.first
require environment if environment
end
initializer :append_asset_paths do
config.asset_path = "/#{engine_name}%s" unless config.asset_path
public_path = config.paths.public.to_a.first
if config.compiled_asset_path && File.exist?(public_path)
config.static_asset_paths[config.compiled_asset_path] = public_path
end
end
initializer :prepend_helpers_path do
unless namespaced?
config.helpers_paths = [] unless config.respond_to?(:helpers_paths)
config.helpers_paths = config.paths.app.helpers.to_a + config.helpers_paths
end
end
initializer :load_config_initializers do
paths.config.initializers.to_a.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
protected
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
Config::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_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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