require "active_support/concern" require "active_support/descendants_tracker" require "active_support/core_ext/array/extract_options" require "active_support/core_ext/class/attribute" require "active_support/core_ext/kernel/reporting" require "active_support/core_ext/kernel/singleton_class" require "active_support/core_ext/string/filters" require "active_support/deprecation" require "thread" module ActiveSupport # Callbacks are code hooks that are run at key points in an object's life cycle. # The typical use case is to have a base class define a set of callbacks # relevant to the other functionality it supplies, so that subclasses can # install callbacks that enhance or modify the base functionality without # needing to override or redefine methods of the base class. # # Mixing in this module allows you to define the events in the object's # life cycle that will support callbacks (via +ClassMethods.define_callbacks+), # set the instance methods, procs, or callback objects to be called (via # +ClassMethods.set_callback+), and run the installed callbacks at the # appropriate times (via +run_callbacks+). # # Three kinds of callbacks are supported: before callbacks, run before a # certain event; after callbacks, run after the event; and around callbacks, # blocks that surround the event, triggering it when they yield. Callback code # can be contained in instance methods, procs or lambdas, or callback objects # that respond to certain predetermined methods. See +ClassMethods.set_callback+ # for details. # # class Record # include ActiveSupport::Callbacks # define_callbacks :save # # def save # run_callbacks :save do # puts "- save" # end # end # end # # class PersonRecord < Record # set_callback :save, :before, :saving_message # def saving_message # puts "saving..." # end # # set_callback :save, :after do |object| # puts "saved" # end # end # # person = PersonRecord.new # person.save # # Output: # saving... # - save # saved module Callbacks extend Concern included do extend ActiveSupport::DescendantsTracker class_attribute :__callbacks, instance_writer: false self.__callbacks ||= {} end CALLBACK_FILTER_TYPES = [:before, :after, :around] # Runs the callbacks for the given event. # # Calls the before and around callbacks in the order they were set, yields # the block (if given one), and then runs the after callbacks in reverse # order. # # If the callback chain was halted, returns +false+. Otherwise returns the # result of the block, +nil+ if no callbacks have been set, or +true+ # if callbacks have been set but no block is given. # # run_callbacks :save do # save # end # #-- # # As this method is used in many places, and often wraps large portions of # user code, it has an additional design goal of minimizing its impact on # the visible call stack. An exception from inside a :before or :after # callback can be as noisy as it likes -- but when control has passed # smoothly through and into the supplied block, we want as little evidence # as possible that we were here. def run_callbacks(kind) callbacks = __callbacks[kind.to_sym] if callbacks.empty? yield if block_given? else env = Filters::Environment.new(self, false, nil) next_sequence = callbacks.compile invoke_sequence = Proc.new do skipped = nil while true current = next_sequence current.invoke_before(env) if current.final? env.value = !env.halted && (!block_given? || yield) elsif current.skip?(env) (skipped ||= []) << current next_sequence = next_sequence.nested next else next_sequence = next_sequence.nested begin target, block, method, *arguments = current.expand_call_template(env, invoke_sequence) target.send(method, *arguments, &block) ensure next_sequence = current end end current.invoke_after(env) skipped.pop.invoke_after(env) while skipped && skipped.first break env.value end end # Common case: no 'around' callbacks defined if next_sequence.final? next_sequence.invoke_before(env) env.value = !env.halted && (!block_given? || yield) next_sequence.invoke_after(env) env.value else invoke_sequence.call end end end private # A hook invoked every time a before callback is halted. # This can be overridden in ActiveSupport::Callbacks implementors in order # to provide better debugging/logging. def halted_callback_hook(filter) end module Conditionals # :nodoc: class Value def initialize(&block) @block = block end def call(target, value); @block.call(value); end end end module Filters Environment = Struct.new(:target, :halted, :value) class Before def self.build(callback_sequence, user_callback, user_conditions, chain_config, filter) halted_lambda = chain_config[:terminator] if user_conditions.any? halting_and_conditional(callback_sequence, user_callback, user_conditions, halted_lambda, filter) else halting(callback_sequence, user_callback, halted_lambda, filter) end end def self.halting_and_conditional(callback_sequence, user_callback, user_conditions, halted_lambda, filter) callback_sequence.before do |env| target = env.target value = env.value halted = env.halted if !halted && user_conditions.all? { |c| c.call(target, value) } result_lambda = -> { user_callback.call target, value } env.halted = halted_lambda.call(target, result_lambda) if env.halted target.send :halted_callback_hook, filter end end env end end private_class_method :halting_and_conditional def self.halting(callback_sequence, user_callback, halted_lambda, filter) callback_sequence.before do |env| target = env.target value = env.value halted = env.halted unless halted result_lambda = -> { user_callback.call target, value } env.halted = halted_lambda.call(target, result_lambda) if env.halted target.send :halted_callback_hook, filter end end env end end private_class_method :halting end class After def self.build(callback_sequence, user_callback, user_conditions, chain_config) if chain_config[:skip_after_callbacks_if_terminated] if user_conditions.any? halting_and_conditional(callback_sequence, user_callback, user_conditions) else halting(callback_sequence, user_callback) end else if user_conditions.any? conditional callback_sequence, user_callback, user_conditions else simple callback_sequence, user_callback end end end def self.halting_and_conditional(callback_sequence, user_callback, user_conditions) callback_sequence.after do |env| target = env.target value = env.value halted = env.halted if !halted && user_conditions.all? { |c| c.call(target, value) } user_callback.call target, value end env end end private_class_method :halting_and_conditional def self.halting(callback_sequence, user_callback) callback_sequence.after do |env| unless env.halted user_callback.call env.target, env.value end env end end private_class_method :halting def self.conditional(callback_sequence, user_callback, user_conditions) callback_sequence.after do |env| target = env.target value = env.value if user_conditions.all? { |c| c.call(target, value) } user_callback.call target, value end env end end private_class_method :conditional def self.simple(callback_sequence, user_callback) callback_sequence.after do |env| user_callback.call env.target, env.value env end end private_class_method :simple end end class Callback #:nodoc:# def self.build(chain, filter, kind, options) if filter.is_a?(String) raise ArgumentError, <<-MSG.squish Passing string to define a callback is not supported. See the `.set_callback` documentation to see supported values. MSG end new chain.name, filter, kind, options, chain.config end attr_accessor :kind, :name attr_reader :chain_config def initialize(name, filter, kind, options, chain_config) @chain_config = chain_config @name = name @kind = kind @filter = filter @key = compute_identifier filter @if = Array(options[:if]) @unless = Array(options[:unless]) end def filter; @key; end def raw_filter; @filter; end def merge_conditional_options(chain, if_option:, unless_option:) options = { if: @if.dup, unless: @unless.dup } options[:if].concat Array(unless_option) options[:unless].concat Array(if_option) self.class.build chain, @filter, @kind, options end def matches?(_kind, _filter) @kind == _kind && filter == _filter end def duplicates?(other) case @filter when Symbol, String matches?(other.kind, other.filter) else false end end # Wraps code with filter def apply(callback_sequence) user_conditions = conditions_lambdas user_callback = CallTemplate.build(@filter, self) case kind when :before Filters::Before.build(callback_sequence, user_callback.make_lambda, user_conditions, chain_config, @filter) when :after Filters::After.build(callback_sequence, user_callback.make_lambda, user_conditions, chain_config) when :around callback_sequence.around(user_callback, user_conditions) end end def current_scopes Array(chain_config[:scope]).map { |s| public_send(s) } end private def compute_identifier(filter) case filter when String, ::Proc filter.object_id else filter end end def conditions_lambdas @if.map { |c| CallTemplate.build(c, self).make_lambda } + @unless.map { |c| CallTemplate.build(c, self).inverted_lambda } end end # A future invocation of user-supplied code (either as a callback, # or a condition filter). class CallTemplate # :nodoc: def initialize(target, method, arguments, block) @override_target = target @method_name = method @arguments = arguments @override_block = block end # Return the parts needed to make this call, with the given # input values. # # Returns an array of the form: # # [target, block, method, *arguments] # # This array can be used as such: # # target.send(method, *arguments, &block) # # The actual invocation is left up to the caller to minimize # call stack pollution. def expand(target, value, block) result = @arguments.map { |arg| case arg when :value; value when :target; target when :block; block || raise(ArgumentError) end } result.unshift @method_name result.unshift @override_block || block result.unshift @override_target || target # target, block, method, *arguments = result # target.send(method, *arguments, &block) result end # Return a lambda that will make this call when given the input # values. def make_lambda lambda do |target, value, &block| target, block, method, *arguments = expand(target, value, block) target.send(method, *arguments, &block) end end # Return a lambda that will make this call when given the input # values, but then return the boolean inverse of that result. def inverted_lambda lambda do |target, value, &block| target, block, method, *arguments = expand(target, value, block) ! target.send(method, *arguments, &block) end end # Filters support: # # Symbols:: A method to call. # Strings:: Some content to evaluate. # Procs:: A proc to call with the object. # Objects:: An object with a before_foo method on it to call. # # All of these objects are converted into a CallTemplate and handled # the same after this point. def self.build(filter, callback) case filter when Symbol new(nil, filter, [], nil) when String new(nil, :instance_exec, [:value], compile_lambda(filter)) when Conditionals::Value new(filter, :call, [:target, :value], nil) when ::Proc if filter.arity > 1 new(nil, :instance_exec, [:target, :block], filter) elsif filter.arity > 0 new(nil, :instance_exec, [:target], filter) else new(nil, :instance_exec, [], filter) end else method_to_call = callback.current_scopes.join("_") new(filter, method_to_call, [:target], nil) end end def self.compile_lambda(filter) eval("lambda { |value| #{filter} }") end end # Execute before and after filters in a sequence instead of # chaining them with nested lambda calls, see: # https://github.com/rails/rails/issues/18011 class CallbackSequence # :nodoc: def initialize(nested = nil, call_template = nil, user_conditions = nil) @nested = nested @call_template = call_template @user_conditions = user_conditions @before = [] @after = [] end def before(&before) @before.unshift(before) self end def after(&after) @after.push(after) self end def around(call_template, user_conditions) CallbackSequence.new(self, call_template, user_conditions) end def skip?(arg) arg.halted || !@user_conditions.all? { |c| c.call(arg.target, arg.value) } end def nested @nested end def final? !@call_template end def expand_call_template(arg, block) @call_template.expand(arg.target, arg.value, block) end def invoke_before(arg) @before.each { |b| b.call(arg) } end def invoke_after(arg) @after.each { |a| a.call(arg) } end end # An Array with a compile method. class CallbackChain #:nodoc:# include Enumerable attr_reader :name, :config def initialize(name, config) @name = name @config = { scope: [:kind], terminator: default_terminator }.merge!(config) @chain = [] @callbacks = nil @mutex = Mutex.new end def each(&block); @chain.each(&block); end def index(o); @chain.index(o); end def empty?; @chain.empty?; end def insert(index, o) @callbacks = nil @chain.insert(index, o) end def delete(o) @callbacks = nil @chain.delete(o) end def clear @callbacks = nil @chain.clear self end def initialize_copy(other) @callbacks = nil @chain = other.chain.dup @mutex = Mutex.new end def compile @callbacks || @mutex.synchronize do final_sequence = CallbackSequence.new @callbacks ||= @chain.reverse.inject(final_sequence) do |callback_sequence, callback| callback.apply callback_sequence end end end def append(*callbacks) callbacks.each { |c| append_one(c) } end def prepend(*callbacks) callbacks.each { |c| prepend_one(c) } end protected def chain; @chain; end private def append_one(callback) @callbacks = nil remove_duplicates(callback) @chain.push(callback) end def prepend_one(callback) @callbacks = nil remove_duplicates(callback) @chain.unshift(callback) end def remove_duplicates(callback) @callbacks = nil @chain.delete_if { |c| callback.duplicates?(c) } end def default_terminator Proc.new do |target, result_lambda| terminate = true catch(:abort) do result_lambda.call if result_lambda.is_a?(Proc) terminate = false end terminate end end end module ClassMethods def normalize_callback_params(filters, block) # :nodoc: type = CALLBACK_FILTER_TYPES.include?(filters.first) ? filters.shift : :before options = filters.extract_options! filters.unshift(block) if block [type, filters, options.dup] end # This is used internally to append, prepend and skip callbacks to the # CallbackChain. def __update_callbacks(name) #:nodoc: ([self] + ActiveSupport::DescendantsTracker.descendants(self)).reverse_each do |target| chain = target.get_callbacks name yield target, chain.dup end end # Install a callback for the given event. # # set_callback :save, :before, :before_method # set_callback :save, :after, :after_method, if: :condition # set_callback :save, :around, ->(r, block) { stuff; result = block.call; stuff } # # The second argument indicates whether the callback is to be run +:before+, # +:after+, or +:around+ the event. If omitted, +:before+ is assumed. This # means the first example above can also be written as: # # set_callback :save, :before_method # # The callback can be specified as a symbol naming an instance method; as a # proc, lambda, or block; or as an object that responds to a certain method # determined by the :scope argument to +define_callbacks+. # # If a proc, lambda, or block is given, its body is evaluated in the context # of the current object. It can also optionally accept the current object as # an argument. # # Before and around callbacks are called in the order that they are set; # after callbacks are called in the reverse order. # # Around callbacks can access the return value from the event, if it # wasn't halted, from the +yield+ call. # # ===== Options # # * :if - A symbol, a string (deprecated) or an array of symbols, # each naming an instance method or a proc; the callback will be called # only when they all return a true value. # * :unless - A symbol, a string (deprecated) or an array of symbols, # each naming an instance method or a proc; the callback will be called # only when they all return a false value. # * :prepend - If +true+, the callback will be prepended to the # existing chain rather than appended. def set_callback(name, *filter_list, &block) type, filters, options = normalize_callback_params(filter_list, block) if options[:if].is_a?(String) || options[:unless].is_a?(String) ActiveSupport::Deprecation.warn(<<-MSG.squish) Passing string to :if and :unless conditional options is deprecated and will be removed in Rails 5.2 without replacement. MSG end self_chain = get_callbacks name mapped = filters.map do |filter| Callback.build(self_chain, filter, type, options) end __update_callbacks(name) do |target, chain| options[:prepend] ? chain.prepend(*mapped) : chain.append(*mapped) target.set_callbacks name, chain end end # Skip a previously set callback. Like +set_callback+, :if or # :unless options may be passed in order to control when the # callback is skipped. # # class Writer < Person # skip_callback :validate, :before, :check_membership, if: -> { age > 18 } # end # # An ArgumentError will be raised if the callback has not # already been set (unless the :raise option is set to false). def skip_callback(name, *filter_list, &block) type, filters, options = normalize_callback_params(filter_list, block) if options[:if].is_a?(String) || options[:unless].is_a?(String) ActiveSupport::Deprecation.warn(<<-MSG.squish) Passing string to :if and :unless conditional options is deprecated and will be removed in Rails 5.2 without replacement. MSG end options[:raise] = true unless options.key?(:raise) __update_callbacks(name) do |target, chain| filters.each do |filter| callback = chain.find { |c| c.matches?(type, filter) } if !callback && options[:raise] raise ArgumentError, "#{type.to_s.capitalize} #{name} callback #{filter.inspect} has not been defined" end if callback && (options.key?(:if) || options.key?(:unless)) new_callback = callback.merge_conditional_options(chain, if_option: options[:if], unless_option: options[:unless]) chain.insert(chain.index(callback), new_callback) end chain.delete(callback) end target.set_callbacks name, chain end end # Remove all set callbacks for the given event. def reset_callbacks(name) callbacks = get_callbacks name ActiveSupport::DescendantsTracker.descendants(self).each do |target| chain = target.get_callbacks(name).dup callbacks.each { |c| chain.delete(c) } target.set_callbacks name, chain end set_callbacks(name, callbacks.dup.clear) end # Define sets of events in the object life cycle that support callbacks. # # define_callbacks :validate # define_callbacks :initialize, :save, :destroy # # ===== Options # # * :terminator - Determines when a before filter will halt the # callback chain, preventing following before and around callbacks from # being called and the event from being triggered. # This should be a lambda to be executed. # The current object and the result lambda of the callback will be provided # to the terminator lambda. # # define_callbacks :validate, terminator: ->(target, result_lambda) { result_lambda.call == false } # # In this example, if any before validate callbacks returns +false+, # any successive before and around callback is not executed. # # The default terminator halts the chain when a callback throws +:abort+. # # * :skip_after_callbacks_if_terminated - Determines if after # callbacks should be terminated by the :terminator option. By # default after callbacks are executed no matter if callback chain was # terminated or not. This option makes sense only when :terminator # option is specified. # # * :scope - Indicates which methods should be executed when an # object is used as a callback. # # class Audit # def before(caller) # puts 'Audit: before is called' # end # # def before_save(caller) # puts 'Audit: before_save is called' # end # end # # class Account # include ActiveSupport::Callbacks # # define_callbacks :save # set_callback :save, :before, Audit.new # # def save # run_callbacks :save do # puts 'save in main' # end # end # end # # In the above case whenever you save an account the method # Audit#before will be called. On the other hand # # define_callbacks :save, scope: [:kind, :name] # # would trigger Audit#before_save instead. That's constructed # by calling #{kind}_#{name} on the given instance. In this # case "kind" is "before" and "name" is "save". In this context +:kind+ # and +:name+ have special meanings: +:kind+ refers to the kind of # callback (before/after/around) and +:name+ refers to the method on # which callbacks are being defined. # # A declaration like # # define_callbacks :save, scope: [:name] # # would call Audit#save. # # ===== Notes # # +names+ passed to +define_callbacks+ must not end with # !, ? or =. # # Calling +define_callbacks+ multiple times with the same +names+ will # overwrite previous callbacks registered with +set_callback+. def define_callbacks(*names) options = names.extract_options! names.each do |name| name = name.to_sym set_callbacks name, CallbackChain.new(name, options) module_eval <<-RUBY, __FILE__, __LINE__ + 1 def _run_#{name}_callbacks(&block) run_callbacks #{name.inspect}, &block end def self._#{name}_callbacks get_callbacks(#{name.inspect}) end def self._#{name}_callbacks=(value) set_callbacks(#{name.inspect}, value) end def _#{name}_callbacks __callbacks[#{name.inspect}] end RUBY end end protected def get_callbacks(name) # :nodoc: __callbacks[name.to_sym] end def set_callbacks(name, callbacks) # :nodoc: self.__callbacks = __callbacks.merge(name.to_sym => callbacks) end end end end