normalizes indentation and whitespace across the project

1 files changed, 560 insertions, 560 deletions

diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index 985f432c7b..a450b0e6d4 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -92,705 +92,705 @@ module ActiveSupport
 
     private
 
-    def __run_callbacks__(callbacks, &block)
-      if callbacks.empty?
-        yield if block_given?
-      else
-        runner = callbacks.compile
-        e = Filters::Environment.new(self, false, nil, block)
-        runner.call(e).value
+      def __run_callbacks__(callbacks, &block)
+        if callbacks.empty?
+          yield if block_given?
+        else
+          runner = callbacks.compile
+          e = Filters::Environment.new(self, false, nil, block)
+          runner.call(e).value
+        end
       end
-    end
 
     # 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
+      def halted_callback_hook(filter)
       end
-    end
-
-    module Filters
-      Environment = Struct.new(:target, :halted, :value, :run_block)
 
-      class End
-        def call(env)
-          block = env.run_block
-          env.value = !env.halted && (!block || block.call)
-          env
+      module Conditionals # :nodoc:
+        class Value
+          def initialize(&block)
+            @block = block
+          end
+          def call(target, value); @block.call(value); end
         end
       end
-      ENDING = End.new
 
-      class Before
-        def self.build(callback_sequence, user_callback, user_conditions, chain_config, filter)
-          halted_lambda = chain_config[:terminator]
+      module Filters
+        Environment = Struct.new(:target, :halted, :value, :run_block)
 
-          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)
+        class End
+          def call(env)
+            block = env.run_block
+            env.value = !env.halted && (!block || block.call)
+            env
           end
         end
+        ENDING = End.new
 
-        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
+        class Before
+          def self.build(callback_sequence, user_callback, user_conditions, chain_config, filter)
+            halted_lambda = chain_config[:terminator]
 
-            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
+            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
 
-            env
+          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
-        end
-        private_class_method :halting_and_conditional
+          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
+          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)
+              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
+                if env.halted
+                  target.send :halted_callback_hook, filter
+                end
               end
-            end
 
-            env
+              env
+            end
           end
+          private_class_method :halting
         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
+        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
-              simple callback_sequence, user_callback
+              if user_conditions.any?
+                conditional callback_sequence, user_callback, user_conditions
+              else
+                simple callback_sequence, user_callback
+              end
             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
+          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
+              if !halted && user_conditions.all? { |c| c.call(target, value) }
+                user_callback.call target, value
+              end
 
-            env
+              env
+            end
           end
-        end
-        private_class_method :halting_and_conditional
+          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
+          def self.halting(callback_sequence, user_callback)
+            callback_sequence.after do |env|
+              unless env.halted
+                user_callback.call env.target, env.value
+              end
 
-            env
+              env
+            end
           end
-        end
-        private_class_method :halting
+          private_class_method :halting
 
-        def self.conditional(callback_sequence, user_callback, user_conditions)
-          callback_sequence.after do |env|
-            target = env.target
-            value  = env.value
+          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
+              if user_conditions.all? { |c| c.call(target, value) }
+                user_callback.call target, value
+              end
 
-            env
+              env
+            end
           end
-        end
-        private_class_method :conditional
+          private_class_method :conditional
 
-        def self.simple(callback_sequence, user_callback)
-          callback_sequence.after do |env|
-            user_callback.call env.target, env.value
+          def self.simple(callback_sequence, user_callback)
+            callback_sequence.after do |env|
+              user_callback.call env.target, env.value
 
-            env
+              env
+            end
           end
+          private_class_method :simple
         end
-        private_class_method :simple
-      end
 
-      class Around
-        def self.build(callback_sequence, user_callback, user_conditions, chain_config)
-          if user_conditions.any?
-            halting_and_conditional(callback_sequence, user_callback, user_conditions)
-          else
-            halting(callback_sequence, user_callback)
+        class Around
+          def self.build(callback_sequence, user_callback, user_conditions, chain_config)
+            if user_conditions.any?
+              halting_and_conditional(callback_sequence, user_callback, user_conditions)
+            else
+              halting(callback_sequence, user_callback)
+            end
           end
-        end
 
-        def self.halting_and_conditional(callback_sequence, user_callback, user_conditions)
-          callback_sequence.around do |env, &run|
-            target = env.target
-            value  = env.value
-            halted = env.halted
-
-            if !halted && user_conditions.all? { |c| c.call(target, value) }
-              user_callback.call(target, value) {
-                run.call.value
-              }
-              env
-            else
-              run.call
+          def self.halting_and_conditional(callback_sequence, user_callback, user_conditions)
+            callback_sequence.around do |env, &run|
+              target = env.target
+              value  = env.value
+              halted = env.halted
+
+              if !halted && user_conditions.all? { |c| c.call(target, value) }
+                user_callback.call(target, value) {
+                  run.call.value
+                }
+                env
+              else
+                run.call
+              end
             end
           end
-        end
-        private_class_method :halting_and_conditional
+          private_class_method :halting_and_conditional
 
-        def self.halting(callback_sequence, user_callback)
-          callback_sequence.around do |env, &run|
-            target = env.target
-            value  = env.value
+          def self.halting(callback_sequence, user_callback)
+            callback_sequence.around do |env, &run|
+              target = env.target
+              value  = env.value
 
-            if env.halted
-              run.call
-            else
-              user_callback.call(target, value) {
-                run.call.value
-              }
-              env
+              if env.halted
+                run.call
+              else
+                user_callback.call(target, value) {
+                  run.call.value
+                }
+                env
+              end
             end
           end
+          private_class_method :halting
         end
-        private_class_method :halting
       end
-    end
 
-    class Callback #:nodoc:#
-      def self.build(chain, filter, kind, options)
-        if filter.is_a?(String)
-          ActiveSupport::Deprecation.warn(<<-MSG.squish)
+      class Callback #:nodoc:#
+        def self.build(chain, filter, kind, options)
+          if filter.is_a?(String)
+            ActiveSupport::Deprecation.warn(<<-MSG.squish)
             Passing string to define callback is deprecated and will be removed
             in Rails 5.1 without replacement.
           MSG
-        end
-
-        new chain.name, filter, kind, options, chain.config
-      end
+          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
+          new chain.name, filter, kind, options, chain.config
+        end
 
-      def filter; @key; end
-      def raw_filter; @filter; 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 merge_conditional_options(chain, if_option:, unless_option:)
-        options = {
-          if: @if.dup,
-          unless: @unless.dup
-        }
+        def filter; @key; end
+        def raw_filter; @filter; end
 
-        options[:if].concat     Array(unless_option)
-        options[:unless].concat Array(if_option)
+        def merge_conditional_options(chain, if_option:, unless_option:)
+          options = {
+            if: @if.dup,
+            unless: @unless.dup
+          }
 
-        self.class.build chain, @filter, @kind, options
-      end
+          options[:if].concat     Array(unless_option)
+          options[:unless].concat Array(if_option)
 
-      def matches?(_kind, _filter)
-        @kind == _kind && filter == _filter
-      end
+          self.class.build chain, @filter, @kind, options
+        end
 
-      def duplicates?(other)
-        case @filter
-        when Symbol, String
-          matches?(other.kind, other.filter)
-        else
-          false
+        def matches?(_kind, _filter)
+          @kind == _kind && filter == _filter
         end
-      end
 
-      # Wraps code with filter
-      def apply(callback_sequence)
-        user_conditions = conditions_lambdas
-        user_callback = make_lambda @filter
-
-        case kind
-        when :before
-          Filters::Before.build(callback_sequence, user_callback, user_conditions, chain_config, @filter)
-        when :after
-          Filters::After.build(callback_sequence, user_callback, user_conditions, chain_config)
-        when :around
-          Filters::Around.build(callback_sequence, user_callback, user_conditions, chain_config)
+        def duplicates?(other)
+          case @filter
+          when Symbol, String
+            matches?(other.kind, other.filter)
+          else
+            false
+          end
         end
-      end
 
-      private
+        # Wraps code with filter
+        def apply(callback_sequence)
+          user_conditions = conditions_lambdas
+          user_callback = make_lambda @filter
+
+          case kind
+          when :before
+            Filters::Before.build(callback_sequence, user_callback, user_conditions, chain_config, @filter)
+          when :after
+            Filters::After.build(callback_sequence, user_callback, user_conditions, chain_config)
+          when :around
+            Filters::Around.build(callback_sequence, user_callback, user_conditions, chain_config)
+          end
+        end
 
-      def invert_lambda(l)
-        lambda { |*args, &blk| !l.call(*args, &blk) }
-      end
+        private
 
-      # 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 <tt>before_foo</tt> method on it to call.
-      #
-      # All of these objects are converted into a lambda and handled
-      # the same after this point.
-      def make_lambda(filter)
-        case filter
-        when Symbol
-          lambda { |target, _, &blk| target.send filter, &blk }
-        when String
-          l = eval "lambda { |value| #{filter} }"
-          lambda { |target, value| target.instance_exec(value, &l) }
-        when Conditionals::Value then filter
-        when ::Proc
-          if filter.arity > 1
-            return lambda { |target, _, &block|
-              raise ArgumentError unless block
-              target.instance_exec(target, block, &filter)
-            }
+          def invert_lambda(l)
+            lambda { |*args, &blk| !l.call(*args, &blk) }
           end
 
-          if filter.arity <= 0
-            lambda { |target, _| target.instance_exec(&filter) }
-          else
-            lambda { |target, _| target.instance_exec(target, &filter) }
-          end
-        else
-          scopes = Array(chain_config[:scope])
-          method_to_call = scopes.map{ |s| public_send(s) }.join("_")
+        # 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 <tt>before_foo</tt> method on it to call.
+        #
+        # All of these objects are converted into a lambda and handled
+        # the same after this point.
+          def make_lambda(filter)
+            case filter
+            when Symbol
+              lambda { |target, _, &blk| target.send filter, &blk }
+            when String
+              l = eval "lambda { |value| #{filter} }"
+              lambda { |target, value| target.instance_exec(value, &l) }
+            when Conditionals::Value then filter
+            when ::Proc
+              if filter.arity > 1
+                return lambda { |target, _, &block|
+                  raise ArgumentError unless block
+                  target.instance_exec(target, block, &filter)
+                }
+              end
 
-          lambda { |target, _, &blk|
-            filter.public_send method_to_call, target, &blk
-          }
-        end
-      end
+              if filter.arity <= 0
+                lambda { |target, _| target.instance_exec(&filter) }
+              else
+                lambda { |target, _| target.instance_exec(target, &filter) }
+              end
+            else
+              scopes = Array(chain_config[:scope])
+              method_to_call = scopes.map{ |s| public_send(s) }.join("_")
 
-      def compute_identifier(filter)
-        case filter
-        when String, ::Proc
-          filter.object_id
-        else
-          filter
-        end
-      end
+              lambda { |target, _, &blk|
+                filter.public_send method_to_call, target, &blk
+              }
+            end
+          end
+
+          def compute_identifier(filter)
+            case filter
+            when String, ::Proc
+              filter.object_id
+            else
+              filter
+            end
+          end
 
-      def conditions_lambdas
-        @if.map { |c| make_lambda c } +
-          @unless.map { |c| invert_lambda make_lambda c }
+          def conditions_lambdas
+            @if.map { |c| make_lambda c } +
+              @unless.map { |c| invert_lambda make_lambda c }
+          end
       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
-      def initialize(&call)
-        @call = call
-        @before = []
-        @after = []
-      end
+      class CallbackSequence
+        def initialize(&call)
+          @call = call
+          @before = []
+          @after = []
+        end
 
-      def before(&before)
-        @before.unshift(before)
-        self
-      end
+        def before(&before)
+          @before.unshift(before)
+          self
+        end
 
-      def after(&after)
-        @after.push(after)
-        self
-      end
+        def after(&after)
+          @after.push(after)
+          self
+        end
 
-      def around(&around)
-        CallbackSequence.new do |arg|
-          around.call(arg) {
-            self.call(arg)
-          }
+        def around(&around)
+          CallbackSequence.new do |arg|
+            around.call(arg) {
+              self.call(arg)
+            }
+          end
         end
-      end
 
-      def call(arg)
-        @before.each { |b| b.call(arg) }
-        value = @call.call(arg)
-        @after.each { |a| a.call(arg) }
-        value
+        def call(arg)
+          @before.each { |b| b.call(arg) }
+          value = @call.call(arg)
+          @after.each { |a| a.call(arg) }
+          value
+        end
       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
+      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 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 insert(index, o)
+          @callbacks = nil
+          @chain.insert(index, o)
+        end
 
-      def delete(o)
-        @callbacks = nil
-        @chain.delete(o)
-      end
+        def delete(o)
+          @callbacks = nil
+          @chain.delete(o)
+        end
 
-      def clear
-        @callbacks = nil
-        @chain.clear
-        self
-      end
+        def clear
+          @callbacks = nil
+          @chain.clear
+          self
+        end
 
-      def initialize_copy(other)
-        @callbacks = nil
-        @chain     = other.chain.dup
-        @mutex     = Mutex.new
-      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 { |env| Filters::ENDING.call(env) }
-          @callbacks ||= @chain.reverse.inject(final_sequence) do |callback_sequence, callback|
-            callback.apply callback_sequence
+        def compile
+          @callbacks || @mutex.synchronize do
+            final_sequence = CallbackSequence.new { |env| Filters::ENDING.call(env) }
+            @callbacks ||= @chain.reverse.inject(final_sequence) do |callback_sequence, callback|
+              callback.apply callback_sequence
+            end
           end
         end
-      end
 
-      def append(*callbacks)
-        callbacks.each { |c| append_one(c) }
-      end
-
-      def prepend(*callbacks)
-        callbacks.each { |c| prepend_one(c) }
-      end
+        def append(*callbacks)
+          callbacks.each { |c| append_one(c) }
+        end
 
-      protected
-      def chain; @chain; end
+        def prepend(*callbacks)
+          callbacks.each { |c| prepend_one(c) }
+        end
 
-      private
+        protected
+          def chain; @chain; end
 
-      def append_one(callback)
-        @callbacks = nil
-        remove_duplicates(callback)
-        @chain.push(callback)
-      end
+        private
 
-      def prepend_one(callback)
-        @callbacks = nil
-        remove_duplicates(callback)
-        @chain.unshift(callback)
-      end
+          def append_one(callback)
+            @callbacks = nil
+            remove_duplicates(callback)
+            @chain.push(callback)
+          end
 
-      def remove_duplicates(callback)
-        @callbacks = nil
-        @chain.delete_if { |c| callback.duplicates?(c) }
-      end
+          def prepend_one(callback)
+            @callbacks = nil
+            remove_duplicates(callback)
+            @chain.unshift(callback)
+          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
+          def remove_duplicates(callback)
+            @callbacks = nil
+            @chain.delete_if { |c| callback.duplicates?(c) }
           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]
+          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
 
-      # 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
+      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
-      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; as a string to be instance evaluated(deprecated); or as an
-      # object that responds to a certain method determined by the <tt>:scope</tt>
-      # 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
-      #
-      # * <tt>:if</tt> - A symbol, a string or an array of symbols and strings,
-      #   each naming an instance method or a proc; the callback will be called
-      #   only when they all return a true value.
-      # * <tt>:unless</tt> - A symbol, a string or an array of symbols and
-      #   strings, each naming an instance method or a proc; the callback will
-      #   be called only when they all return a false value.
-      # * <tt>:prepend</tt> - 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)
-        self_chain = get_callbacks name
-        mapped = filters.map do |filter|
-          Callback.build(self_chain, filter, type, options)
+        # 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
 
-        __update_callbacks(name) do |target, chain|
-          options[:prepend] ? chain.prepend(*mapped) : chain.append(*mapped)
-          target.set_callbacks name, chain
+        # 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; as a string to be instance evaluated(deprecated); or as an
+        # object that responds to a certain method determined by the <tt>:scope</tt>
+        # 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
+        #
+        # * <tt>:if</tt> - A symbol, a string or an array of symbols and strings,
+        #   each naming an instance method or a proc; the callback will be called
+        #   only when they all return a true value.
+        # * <tt>:unless</tt> - A symbol, a string or an array of symbols and
+        #   strings, each naming an instance method or a proc; the callback will
+        #   be called only when they all return a false value.
+        # * <tt>:prepend</tt> - 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)
+          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
-      end
 
-      # Skip a previously set callback. Like +set_callback+, <tt>:if</tt> or
-      # <tt>:unless</tt> options may be passed in order to control when the
-      # callback is skipped.
-      #
-      #   class Writer < Person
-      #      skip_callback :validate, :before, :check_membership, if: -> { self.age > 18 }
-      #   end
-      #
-      # An <tt>ArgumentError</tt> will be raised if the callback has not
-      # already been set (unless the <tt>:raise</tt> option is set to <tt>false</tt>).
-      def skip_callback(name, *filter_list, &block)
-        type, filters, options = normalize_callback_params(filter_list, block)
-        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
+        # Skip a previously set callback. Like +set_callback+, <tt>:if</tt> or
+        # <tt>:unless</tt> options may be passed in order to control when the
+        # callback is skipped.
+        #
+        #   class Writer < Person
+        #      skip_callback :validate, :before, :check_membership, if: -> { self.age > 18 }
+        #   end
+        #
+        # An <tt>ArgumentError</tt> will be raised if the callback has not
+        # already been set (unless the <tt>:raise</tt> option is set to <tt>false</tt>).
+        def skip_callback(name, *filter_list, &block)
+          type, filters, options = normalize_callback_params(filter_list, block)
+          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
+              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)
+              chain.delete(callback)
+            end
+            target.set_callbacks name, chain
           end
-          target.set_callbacks name, chain
         end
-      end
 
-      # Remove all set callbacks for the given event.
-      def reset_callbacks(name)
-        callbacks = get_callbacks name
+        # 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
+          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
 
-        self.set_callbacks name, callbacks.dup.clear
-      end
+          self.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
-      #
-      # * <tt>:terminator</tt> - 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+.
-      #
-      # * <tt>:skip_after_callbacks_if_terminated</tt> - Determines if after
-      #   callbacks should be terminated by the <tt>:terminator</tt> option. By
-      #   default after callbacks are executed no matter if callback chain was
-      #   terminated or not. This option makes sense only when <tt>:terminator</tt>
-      #   option is specified.
-      #
-      # * <tt>:scope</tt> - 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
-      #   <tt>Audit#before</tt> will be called. On the other hand
-      #
-      #     define_callbacks :save, scope: [:kind, :name]
-      #
-      #   would trigger <tt>Audit#before_save</tt> instead. That's constructed
-      #   by calling <tt>#{kind}_#{name}</tt> 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 <tt>Audit#save</tt>.
-      #
-      # ===== 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|
-          class_attribute "_#{name}_callbacks", instance_writer: false
-          set_callbacks name, CallbackChain.new(name, options)
-
-          module_eval <<-RUBY, __FILE__, __LINE__ + 1
+        # Define sets of events in the object life cycle that support callbacks.
+        #
+        #   define_callbacks :validate
+        #   define_callbacks :initialize, :save, :destroy
+        #
+        # ===== Options
+        #
+        # * <tt>:terminator</tt> - 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+.
+        #
+        # * <tt>:skip_after_callbacks_if_terminated</tt> - Determines if after
+        #   callbacks should be terminated by the <tt>:terminator</tt> option. By
+        #   default after callbacks are executed no matter if callback chain was
+        #   terminated or not. This option makes sense only when <tt>:terminator</tt>
+        #   option is specified.
+        #
+        # * <tt>:scope</tt> - 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
+        #   <tt>Audit#before</tt> will be called. On the other hand
+        #
+        #     define_callbacks :save, scope: [:kind, :name]
+        #
+        #   would trigger <tt>Audit#before_save</tt> instead. That's constructed
+        #   by calling <tt>#{kind}_#{name}</tt> 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 <tt>Audit#save</tt>.
+        #
+        # ===== 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|
+            class_attribute "_#{name}_callbacks", instance_writer: false
+            set_callbacks name, CallbackChain.new(name, options)
+
+            module_eval <<-RUBY, __FILE__, __LINE__ + 1
             def _run_#{name}_callbacks(&block)
               __run_callbacks__(_#{name}_callbacks, &block)
             end
           RUBY
+          end
         end
-      end
 
-      protected
+        protected
 
-      def get_callbacks(name) # :nodoc:
-        send "_#{name}_callbacks"
-      end
+          def get_callbacks(name) # :nodoc:
+            send "_#{name}_callbacks"
+          end
 
-      def set_callbacks(name, callbacks) # :nodoc:
-        send "_#{name}_callbacks=", callbacks
-      end
+          def set_callbacks(name, callbacks) # :nodoc:
+            send "_#{name}_callbacks=", callbacks
+          end
 
-      def deprecated_false_terminator # :nodoc:
-        Proc.new do |target, result_lambda|
-          terminate = true
-          catch(:abort) do
-            result = result_lambda.call if result_lambda.is_a?(Proc)
-            if Callbacks.halt_and_display_warning_on_return_false && result == false
-              display_deprecation_warning_for_false_terminator
-            else
-              terminate = false
+          def deprecated_false_terminator # :nodoc:
+            Proc.new do |target, result_lambda|
+              terminate = true
+              catch(:abort) do
+                result = result_lambda.call if result_lambda.is_a?(Proc)
+                if Callbacks.halt_and_display_warning_on_return_false && result == false
+                  display_deprecation_warning_for_false_terminator
+                else
+                  terminate = false
+                end
+              end
+              terminate
             end
           end
-          terminate
-        end
-      end
 
-      private
+        private
 
-      def display_deprecation_warning_for_false_terminator
-        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          def display_deprecation_warning_for_false_terminator
+            ActiveSupport::Deprecation.warn(<<-MSG.squish)
           Returning `false` in Active Record and Active Model callbacks will not implicitly halt a callback chain in Rails 5.1.
           To explicitly halt the callback chain, please use `throw :abort` instead.
         MSG
+          end
       end
-    end
   end
 end