require 'concurrent/map' require 'action_view/dependency_tracker' require 'monitor' module ActionView class Digestor @@digest_monitor = Monitor.new class PerRequestDigestCacheExpiry < Struct.new(:app) # :nodoc: def call(env) ActionView::LookupContext::DetailsKey.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(name:, finder:, **options) options.assert_valid_keys(:dependencies, :partial) cache_key = ([ name ].compact + Array.wrap(options[:dependencies])).join('.') # this is a correctly done double-checked locking idiom # (Concurrent::Map's lookups have volatile semantics) finder.digest_cache[cache_key] || @@digest_monitor.synchronize do finder.digest_cache.fetch(cache_key) do # re-check under lock compute_and_store_digest(cache_key, name, finder, options) end end end private def compute_and_store_digest(cache_key, name, finder, options) # called under @@digest_monitor lock klass = if options[:partial] || 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 = finder.digest_cache.put_if_absent(cache_key, false).nil? # put_if_absent returns nil on insertion PartialDigestor else Digestor end finder.digest_cache[cache_key] = stored_digest = klass.new(name, finder, options).digest ensure # something went wrong or ActionView::Resolver.caching? is false, make sure not to corrupt the @@cache finder.digest_cache.delete_pair(cache_key, false) if pre_stored && !stored_digest end end attr_reader :name, :finder, :options def initialize(name, finder, options = {}) @name, @finder = name, finder @options = options end def digest Digest::MD5.hexdigest("#{source}-#{dependency_digest}").tap do |digest| logger.debug " Cache digest for #{template.inspect}: #{digest}" end rescue ActionView::MissingTemplate logger.error " Couldn't find template for digesting: #{name}" '' end def dependencies DependencyTracker.find_dependencies(name, template, finder.view_paths) rescue ActionView::MissingTemplate logger.error " '#{name}' file doesn't exist, so no dependencies" [] end def nested_dependencies dependencies.collect do |dependency| dependencies = PartialDigestor.new(dependency, finder).nested_dependencies dependencies.any? ? { dependency => dependencies } : dependency end end private class NullLogger def self.debug(_); end def self.error(_); end end def logger ActionView::Base.logger || NullLogger 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