require 'concurrent/map' require 'action_view/dependency_tracker' require 'monitor' module ActionView class Digestor cattr_reader(:cache) @@cache = Concurrent::Map.new @@digest_monitor = Monitor.new class PerRequestDigestCacheExpiry < Struct.new(:app) # :nodoc: def call(env) ActionView::Digestor.cache.clear app.call(env) end end class << self # Supported options: # # * name - Template name # * finder - An instance of ActionView::LookupContext # * dependencies - An array of dependent views # * partial - Specifies whether the template is a partial def digest(options) options.assert_valid_keys(:name, :finder, :dependencies, :partial) cache_key = ([ options[:name], options[:finder].details_key.hash ].compact + Array.wrap(options[:dependencies])).join('.') # this is a correctly done double-checked locking idiom # (Concurrent::Map's lookups have volatile semantics) @@cache[cache_key] || @@digest_monitor.synchronize do @@cache.fetch(cache_key) do # re-check under lock compute_and_store_digest(cache_key, options) end end end private def compute_and_store_digest(cache_key, options) # called under @@digest_monitor lock klass = if options[:partial] || options[:name].include?("/_") # Prevent re-entry or else recursive templates will blow the stack. # There is no need to worry about other threads seeing the +false+ value, # as they will then have to wait for this thread to let go of the @@digest_monitor lock. pre_stored = @@cache.put_if_absent(cache_key, false).nil? # put_if_absent returns nil on insertion PartialDigestor else Digestor end @@cache[cache_key] = stored_digest = klass.new(options).digest ensure # something went wrong or ActionView::Resolver.caching? is false, make sure not to corrupt the @@cache @@cache.delete_pair(cache_key, false) if pre_stored && !stored_digest end end attr_reader :name, :finder, :options def initialize(options) @name, @finder = options.values_at(:name, :finder) @options = options.except(:name, :finder) end def digest Digest::MD5.hexdigest("#{source}-#{dependency_digest}").tap do |digest| logger.try :debug, " Cache digest for #{template.inspect}: #{digest}" end rescue ActionView::MissingTemplate logger.try :error, " Couldn't find template for digesting: #{name}" '' end def dependencies DependencyTracker.find_dependencies(name, template, finder.view_paths) rescue ActionView::MissingTemplate logger.try :error, " '#{name}' file doesn't exist, so no dependencies" [] end def nested_dependencies dependencies.collect do |dependency| dependencies = PartialDigestor.new(name: dependency, finder: finder).nested_dependencies dependencies.any? ? { dependency => dependencies } : dependency end end private def logger ActionView::Base.logger end def logical_name name.gsub(%r|/_|, "/") end def partial? false end def template @template ||= finder.disable_cache { finder.find(logical_name, [], partial?) } end def source template.source end def dependency_digest template_digests = dependencies.collect do |template_name| Digestor.digest(name: template_name, finder: finder, partial: true) end (template_digests + injected_dependencies).join("-") end def injected_dependencies Array.wrap(options[:dependencies]) end end class PartialDigestor < Digestor # :nodoc: def partial? true end end end