require 'forwardable'
require 'active_support/core_ext/class/attribute'
require 'middleman-core/configuration'
require 'middleman-core/contracts'
module Middleman
# Middleman's Extension API provides the ability to add functionality to Middleman
# and to customize existing features. Internally, most features in Middleman are
# implemented as extensions. A good way to figure out how to write your own extension
# is to look at the source of the built-in extensions or popular extension gems like
# `middleman-blog` or `middleman-syntax`.
#
# The most basic extension looks like:
#
# class MyFeature < Middleman::Extension
# def initialize(app, options_hash={}, &block)
# super
# end
# end
# ::Middleman::Extensions.register(:my_feature, MyFeature)
#
# A more complicated example might look like:
#
# class MyFeature < Middleman::Extension
# option :my_option, 'cool', 'A very cool option'
#
# def initialize(app, options_hash={}, &block)
# super
# puts "My option is #{options.my_option}"
# end
#
# def after_configuration
# puts "The project has been configured"
# end
#
# def manipulate_resource_list(resources)
# resources.each do |resource|
# # Make all .jpg's get built or served with a .jpeg extension.
# if resource.ext == '.jpg'
# resource.destination_path = resource.destination_path.sub('.jpg', '.jpeg')
# end
# end
# end
# end
#
# ::Middleman::Extensions.register :my_feature do
# MyFeature
# end
#
# Extensions can add helpers (via {Extension.helpers}), add to the sitemap or change it (via {#manipulate_resource_list}), or run
# arbitrary code at different parts of the Middleman application's lifecycle. They can have options (defined via {Extension.option} and accessed via {#options}).
#
# Common lifecycle events can be handled by extensions simply by implementing an appropriately-named method:
#
# * {#after_configuration}
# * {#after_build}
# * {#before_build}
#
# There are also some less common hooks that can be listened to from within an extension's `initialize` method:
#
# * `app.before_render {|body, path, locs, template_class| ... }` - Manipulate template sources before they are rendered.
# * `app.after_render {|content, path, locs, template_class| ... }` - Manipulate output text after a template has been rendered. It is also common to install a Rack middleware to do this instead.
# * `app.ready { ... }` - Run code once Middleman is ready to serve or build files (after `after_configuration`).
#
# @see http://middlemanapp.com/advanced/custom/ Middleman Custom Extensions Documentation
class Extension
extend Forwardable
include Contracts
def_delegator :@app, :logger
# @!attribute supports_multiple_instances
# @!scope class
# @return [Boolean] whether or not an extension can be activated multiple times, generating multiple instances of the extension.
# By default extensions can only be activated once in a project. This is an advanced option.
class_attribute :supports_multiple_instances, instance_reader: false, instance_writer: false
# @!attribute defined_helpers
# @!scope class
# @api private
# @return [Array<Module>] a list of all the helper modules this extension provides. Set these using {#helpers}.
class_attribute :defined_helpers, instance_reader: false, instance_writer: false
# @!attribute exposed_to_application
# @!scope class
# @api private
# @return [Hash<Symbol, Symbol>] a list of all the methods modules this extension exposes to app. Set these using {#expose_to_application}.
class_attribute :exposed_to_application, instance_reader: false, instance_writer: false
# @!attribute exposed_to_config
# @!scope class
# @api private
# @return [Hash<Symbol, Symbol>] a list of all the methods modules this extension exposes to config. Set these using {#expose_to_config}.
class_attribute :exposed_to_config, instance_reader: false, instance_writer: false
# @!attribute exposed_to_template
# @!scope class
# @api private
# @return [Hash<Symbol, Symbol>] a list of all the methods modules this extension exposes to templates. Set these using {#expose_to_template}.
class_attribute :exposed_to_template, instance_reader: false, instance_writer: false
# @!attribute exposed_to_template
# @!scope class
# @api private
# @return [Array<Any>] a list of method generators.
class_attribute :resources_generators, instance_reader: false, instance_writer: false
# @!attribute ext_name
# @!scope class
# @return [Symbol] the name this extension is registered under. This is the symbol used to activate the extension.
class_attribute :ext_name, instance_reader: false, instance_writer: false
# @!attribute resource_list_manipulator_priority
# @!scope class
# @return [Numeric] the priority for this extension's `manipulate_resource_list` method, if it has one.
# @see Middleman::Sitemap::Store#register_resource_list_manipulator
class_attribute :resource_list_manipulator_priority, instance_reader: false, instance_writer: false
class << self
# @api private
# @return [Middleman::Configuration::ConfigurationManager] The defined options for this extension.
def config
@_config ||= ::Middleman::Configuration::ConfigurationManager.new
end
# Add an option to this extension.
# @see Middleman::Configuration::ConfigurationManager#define_setting
# @example
# option :compress, false, 'Whether to compress the output'
# @param [Symbol] key The name of the option
# @param [Object] default The default value for the option
# @param [String] description A human-readable description of what the option does
def option(key, default=nil, description=nil, options={})
config.define_setting(key, default, description, options)
end
# Short-hand for simple Sitemap manipulation
# @example A generator which returns an array of resources
# resources :make_resources
# @example A generator which maps a path to a method
# resources make_resource: :make_it
# @example A generator which maps a path to a string
# resources make_resource: 'Hello'
# @param [Array] generators The generator definitions
def resources(*generators)
self.resources_generators ||= []
self.resources_generators += generators
end
# Declare helpers to be added the global Middleman application.
# This accepts either a list of modules to add on behalf
# of this extension, or a block whose contents will all
# be used as helpers in a new module.
# @example With a block:
# helpers do
# def my_helper
# "I helped!"
# end
# end
# @example With modules:
# helpers FancyHelpers, PlainHelpers
# @param [Array<Module>] modules An optional list of modules to add as helpers
# @param [Proc] block A block which will be evaluated to create a new helper module
# @return [void]
def helpers(*modules, &block)
self.defined_helpers ||= []
if block_given?
mod = Module.new
mod.module_eval(&block)
modules = [mod]
end
self.defined_helpers += modules
end
# Takes a method within this extension and exposes it globally
# on the main `app` instance. Used for very low-level extensions
# which many other extensions depend upon. Such as Data and
# File watching.
# @example with Hash:
# expose_to_application global_name: :local_name
# @example with Array:
# expose_to_application :method1, :method2
# @param [Array<Sumbol>, Hash<Symbol, Symbol>] symbols An optional list of symbols representing instance methods to exposed.
# @return [void]
def expose_to_application(*symbols)
self.exposed_to_application ||= {}
if symbols.first && symbols.first.is_a?(Hash)
self.exposed_to_application.merge!(symbols.first)
elsif symbols.is_a? Array
symbols.each do |sym|
self.exposed_to_application[sym] = sym
end
end
end
# Takes a method within this extension and exposes it inside the scope
# of the config.rb sandbox.
# @example with Hash:
# expose_to_config global_name: :local_name
# @example with Array:
# expose_to_config :method1, :method2
# @param [Array<Sumbol>, Hash<Symbol, Symbol>] symbols An optional list of symbols representing instance methods to exposed.
# @return [void]
def expose_to_config(*symbols)
self.exposed_to_config ||= {}
if symbols.first && symbols.first.is_a?(Hash)
self.exposed_to_config.merge!(symbols.first)
elsif symbols.is_a? Array
symbols.each do |sym|
self.exposed_to_config[sym] = sym
end
end
end
# Takes a method within this extension and exposes it inside the scope
# of the templating engine. Like `helpers`, but scoped.
# @example with Hash:
# expose_to_template global_name: :local_name
# @example with Array:
# expose_to_template :method1, :method2
# @param [Array<Sumbol>, Hash<Symbol, Symbol>] symbols An optional list of symbols representing instance methods to exposed.
# @return [void]
def expose_to_template(*symbols)
self.exposed_to_template ||= {}
if symbols.first && symbols.first.is_a?(Hash)
self.exposed_to_template.merge!(symbols.first)
elsif symbols.is_a? Array
symbols.each do |sym|
self.exposed_to_template[sym] = sym
end
end
end
# Reset all {Extension.after_extension_activated} callbacks.
# @api private
# @return [void]
def clear_after_extension_callbacks
@_extension_activation_callbacks = {}
end
# Register to run a block after a named extension is activated.
# @param [Symbol] name The name the extension was registered under
# @param [Proc] block A callback to run when the named extension is activated
# @return [void]
def after_extension_activated(name, &block)
@_extension_activation_callbacks ||= {}
@_extension_activation_callbacks[name] ||= []
@_extension_activation_callbacks[name] << block if block_given?
end
# Notify that a particular extension has been activated and run all
# registered {Extension.after_extension_activated} callbacks.
# @api private
# @param [Middleman::Extension] instance Activated extension instance
# @return [void]
def activated_extension(instance)
name = instance.class.ext_name
return unless @_extension_activation_callbacks && @_extension_activation_callbacks.key?(name)
@_extension_activation_callbacks[name].each do |block|
block.arity == 1 ? block.call(instance) : block.call
end
end
end
# @return [Middleman::Configuration::ConfigurationManager] options for this extension instance.
attr_reader :options
# @return [Middleman::Application] the Middleman application instance.
attr_reader :app
# @!method after_extension_activated(name, &block)
# Register to run a block after a named extension is activated.
# @param [Symbol] name The name the extension was registered under
# @param [Proc] block A callback to run when the named extension is activated
# @return [void]
def_delegator :"::Middleman::Extension", :after_extension_activated
# Extensions are instantiated when they are activated.
# @param [Middleman::Application] app The Middleman::Application instance
# @param [Hash] options_hash The raw options hash. Subclasses should not manipulate this directly - it will be turned into {#options}.
# @yield An optional block that can be used to customize options before the extension is activated.
# @yieldparam [Middleman::Configuration::ConfigurationManager] options Extension options
def initialize(app, options_hash={}, &block)
@_helpers = []
@app = app
expose_methods
setup_options(options_hash, &block)
# Bind app hooks to local methods
bind_before_configuration
bind_after_configuration
bind_before_build
bind_after_build
bind_ready
end
# @!method before_configuration
# Respond to the `before_configuration` event.
# If a `before_configuration` method is implemented, that method will be run before `config.rb` is run.
# @note Because most extensions are activated from within `config.rb`, they *will not run* any `before_configuration` hook.
# @!method after_configuration
# Respond to the `after_configuration` event.
# If an `after_configuration` method is implemented, that method will be run before `config.rb` is run.
# @!method before_build
# Respond to the `before_build` event.
# If an `before_build` method is implemented, that method will be run before the builder runs.
# @!method after_build
# Respond to the `after_build` event.
# If an `after_build` method is implemented, that method will be run after the builder runs.
# @!method ready
# Respond to the `ready` event.
# If an `ready` method is implemented, that method will be run after the app has finished booting up.
# @!method manipulate_resource_list(resources)
# Manipulate the resource list by transforming or adding {Sitemap::Resource}s.
# Sitemap manipulation is a powerful way of interacting with a project, since it can modify each {Sitemap::Resource} or generate new {Sitemap::Resources}. This method is used in a pipeline where each sitemap manipulator is run in turn, with each one being fed the output of the previous manipulator. See the source of built-in Middleman extensions like {Middleman::Extensions::DirectoryIndexes} and {Middleman::Extensions::AssetHash} for examples of how to use this.
# @note This method *must* return the full set of resources, because its return value will be used as the new sitemap.
# @see http://middlemanapp.com/advanced/sitemap/ Sitemap Documentation
# @see Sitemap::Store
# @see Sitemap::Resource
# @param [Array<Sitemap::Resource>] resources A list of all the resources known to the sitemap.
# @return [Array<Sitemap::Resource>] The transformed list of resources.
def add_exposed_to_context(context)
(self.class.exposed_to_template || {}).each do |k, v|
context.define_singleton_method(k, &method(v))
end
end
private
def expose_methods
(self.class.exposed_to_application || {}).each do |k, v|
app.define_singleton_method(k, &method(v))
end
(self.class.exposed_to_config || {}).each do |k, v|
app.config_context.define_singleton_method(k, &method(v))
end
(self.class.defined_helpers || []).each do |m|
app.template_context_class.send(:include, m)
end
end
# @yield An optional block that can be used to customize options before the extension is activated.
# @yieldparam Middleman::Configuration::ConfigurationManager] options Extension options
def setup_options(options_hash)
@options = self.class.config.dup
@options.finalize!
options_hash.each do |k, v|
@options[k] = v
end
yield @options, self if block_given?
@options.all_settings.each do |o|
next unless o.options[:required] && !o.value_set?
logger.error "The `:#{o.key}` option of the `#{self.class.ext_name}` extension is required."
exit(1)
end
end
def bind_before_configuration
@app.before_configuration(&method(:before_configuration)) if respond_to?(:before_configuration)
end
def bind_after_configuration
ext = self
@app.after_configuration do
ext.after_configuration if ext.respond_to?(:after_configuration)
if ext.respond_to?(:manipulate_resource_list)
ext.app.sitemap.register_resource_list_manipulator(ext.class.ext_name, ext, ext.class.resource_list_manipulator_priority)
end
if ext.class.resources_generators && !ext.class.resources_generators.empty?
ext.app.sitemap.register_resource_list_manipulator(
:"#{ext.class.ext_name}_generator",
ext,
ext.class.resource_list_manipulator_priority,
:generate_resources
)
end
end
end
def generate_resources(resources)
generator_defs = self.class.resources_generators.reduce({}) do |sum, g|
resource_definitions = if g.is_a? Hash
g
elsif g.is_a? Symbol
definition = method(g)
if definition.arity == 0
send(g)
else
send(g, resources)
end
else
{}
end
sum.merge(resource_definitions)
end
resources + generator_defs.map do |path, g|
if g.is_a? Symbol
definition = method(g)
g = if definition.arity == 0
send(g)
else
send(g, resources)
end
end
::Middleman::Sitemap::StringResource.new(
app.sitemap,
path,
g
)
end
end
def bind_before_build
ext = self
return unless ext.respond_to?(:before_build)
@app.before_build do |builder|
if ext.method(:before_build).arity == 1
ext.before_build(builder)
else
ext.before_build
end
end
end
def bind_after_build
ext = self
return unless ext.respond_to?(:after_build)
@app.after_build do |builder|
if ext.method(:after_build).arity == 1
ext.after_build(builder)
elsif ext.method(:after_build).arity == 2
ext.after_build(builder, builder.thor)
else
ext.after_build
end
end
end
def bind_ready
@app.ready(&method(:ready)) if respond_to?(:ready)
end
end
end