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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:
#
# * <tt>name</tt> - Template name
# * <tt>finder</tt> - An instance of <tt>ActionView::LookupContext</tt>
# * <tt>dependencies</tt> - An array of dependent views
# * <tt>partial</tt> - Specifies whether the template is a partial
def digest(name:, finder:, **options)
options.assert_valid_keys(:dependencies, :partial)
cache_key = ([ name, 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, 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 = @@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(name, finder, 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(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
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