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require_dependency 'declarative_policy/cache'
require_dependency 'declarative_policy/condition'
require_dependency 'declarative_policy/dsl'
require_dependency 'declarative_policy/preferred_scope'
require_dependency 'declarative_policy/rule'
require_dependency 'declarative_policy/runner'
require_dependency 'declarative_policy/step'
require_dependency 'declarative_policy/base'
require 'thread'
module DeclarativePolicy
CLASS_CACHE_MUTEX = Mutex.new
CLASS_CACHE_IVAR = :@__DeclarativePolicy_CLASS_CACHE
class << self
def policy_for(user, subject, opts = {})
cache = opts[:cache] || {}
key = Cache.policy_key(user, subject)
cache[key] ||= class_for(subject).new(user, subject, opts)
end
def class_for(subject)
return GlobalPolicy if subject == :global
return NilPolicy if subject.nil?
subject = find_delegate(subject)
class_for_class(subject.class)
end
private
# This method is heavily cached because there are a lot of anonymous
# modules in play in a typical rails app, and #name performs quite
# slowly for anonymous classes and modules.
#
# See https://bugs.ruby-lang.org/issues/11119
#
# if the above bug is resolved, this caching could likely be removed.
def class_for_class(subject_class)
unless subject_class.instance_variable_defined?(CLASS_CACHE_IVAR)
CLASS_CACHE_MUTEX.synchronize do
# re-check in case of a race
break if subject_class.instance_variable_defined?(CLASS_CACHE_IVAR)
policy_class = compute_class_for_class(subject_class)
subject_class.instance_variable_set(CLASS_CACHE_IVAR, policy_class)
end
end
policy_class = subject_class.instance_variable_get(CLASS_CACHE_IVAR)
raise "no policy for #{subject.class.name}" if policy_class.nil?
policy_class
end
def compute_class_for_class(subject_class)
subject_class.ancestors.each do |klass|
next unless klass.name
begin
policy_class = "#{klass.name}Policy".constantize
# NOTE: the < operator here tests whether policy_class
# inherits from Base. We can't use #is_a? because that
# tests for *instances*, not *subclasses*.
return policy_class if policy_class < Base
rescue NameError
nil
end
end
end
def find_delegate(subject)
seen = Set.new
while subject.respond_to?(:declarative_policy_delegate)
raise ArgumentError, "circular delegations" if seen.include?(subject.object_id)
seen << subject.object_id
subject = subject.declarative_policy_delegate
end
subject
end
end
end
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