Merge branch 'master' into make-reverse-merge-bang-order-consistent

114 files changed, 633 insertions, 311 deletions

diff --git a/activesupport/lib/active_support/core_ext/array.rb b/activesupport/lib/active_support/core_ext/array.rb
index e908386a1c..fdc209ef68 100644
--- a/activesupport/lib/active_support/core_ext/array.rb
+++ b/activesupport/lib/active_support/core_ext/array.rb
@@ -1,7 +1,9 @@
-require "active_support/core_ext/array/wrap"
-require "active_support/core_ext/array/access"
-require "active_support/core_ext/array/conversions"
-require "active_support/core_ext/array/extract_options"
-require "active_support/core_ext/array/grouping"
-require "active_support/core_ext/array/prepend_and_append"
-require "active_support/core_ext/array/inquiry"
+# frozen_string_literal: true
+
+require_relative "array/wrap"
+require_relative "array/access"
+require_relative "array/conversions"
+require_relative "array/extract_options"
+require_relative "array/grouping"
+require_relative "array/prepend_and_append"
+require_relative "array/inquiry"
diff --git a/activesupport/lib/active_support/core_ext/array/access.rb b/activesupport/lib/active_support/core_ext/array/access.rb
index fca33c9d69..d67f99df0e 100644
--- a/activesupport/lib/active_support/core_ext/array/access.rb
+++ b/activesupport/lib/active_support/core_ext/array/access.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Array
   # Returns the tail of the array from +position+.
   #
diff --git a/activesupport/lib/active_support/core_ext/array/conversions.rb b/activesupport/lib/active_support/core_ext/array/conversions.rb
index cac15e1100..6e17a81f0f 100644
--- a/activesupport/lib/active_support/core_ext/array/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/array/conversions.rb
@@ -1,8 +1,10 @@
-require "active_support/xml_mini"
-require "active_support/core_ext/hash/keys"
-require "active_support/core_ext/string/inflections"
-require "active_support/core_ext/object/to_param"
-require "active_support/core_ext/object/to_query"
+# frozen_string_literal: true
+
+require_relative "../../xml_mini"
+require_relative "../hash/keys"
+require_relative "../string/inflections"
+require_relative "../object/to_param"
+require_relative "../object/to_query"
 
 class Array
   # Converts the array to a comma-separated sentence where the last element is
@@ -179,7 +181,7 @@ class Array
   #   </messages>
   #
   def to_xml(options = {})
-    require "active_support/builder" unless defined?(Builder)
+    require_relative "../../builder" unless defined?(Builder)
 
     options = options.dup
     options[:indent]  ||= 2
diff --git a/activesupport/lib/active_support/core_ext/array/extract_options.rb b/activesupport/lib/active_support/core_ext/array/extract_options.rb
index 9008a0df2a..8c7cb2e780 100644
--- a/activesupport/lib/active_support/core_ext/array/extract_options.rb
+++ b/activesupport/lib/active_support/core_ext/array/extract_options.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Hash
   # By default, only instances of Hash itself are extractable.
   # Subclasses of Hash may implement this method and return
diff --git a/activesupport/lib/active_support/core_ext/array/grouping.rb b/activesupport/lib/active_support/core_ext/array/grouping.rb
index 0d798e5c4e..67e760bc4b 100644
--- a/activesupport/lib/active_support/core_ext/array/grouping.rb
+++ b/activesupport/lib/active_support/core_ext/array/grouping.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Array
   # Splits or iterates over the array in groups of size +number+,
   # padding any remaining slots with +fill_with+ unless it is +false+.
diff --git a/activesupport/lib/active_support/core_ext/array/inquiry.rb b/activesupport/lib/active_support/core_ext/array/inquiry.rb
index 66fa5fcd0c..4f4a9fa361 100644
--- a/activesupport/lib/active_support/core_ext/array/inquiry.rb
+++ b/activesupport/lib/active_support/core_ext/array/inquiry.rb
@@ -1,4 +1,6 @@
-require "active_support/array_inquirer"
+# frozen_string_literal: true
+
+require_relative "../../array_inquirer"
 
 class Array
   # Wraps the array in an +ArrayInquirer+ object, which gives a friendlier way
diff --git a/activesupport/lib/active_support/core_ext/array/prepend_and_append.rb b/activesupport/lib/active_support/core_ext/array/prepend_and_append.rb
index 16a6789f8d..661971d7cd 100644
--- a/activesupport/lib/active_support/core_ext/array/prepend_and_append.rb
+++ b/activesupport/lib/active_support/core_ext/array/prepend_and_append.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 class Array
   # The human way of thinking about adding stuff to the end of a list is with append.
-  alias_method :append,  :<<
+  alias_method :append,  :push unless [].respond_to?(:append)
 
   # The human way of thinking about adding stuff to the beginning of a list is with prepend.
-  alias_method :prepend, :unshift
+  alias_method :prepend, :unshift unless [].respond_to?(:prepend)
 end
diff --git a/activesupport/lib/active_support/core_ext/array/wrap.rb b/activesupport/lib/active_support/core_ext/array/wrap.rb
index b611d34c27..d62f97edbf 100644
--- a/activesupport/lib/active_support/core_ext/array/wrap.rb
+++ b/activesupport/lib/active_support/core_ext/array/wrap.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Array
   # Wraps its argument in an array unless it is already an array (or array-like).
   #
diff --git a/activesupport/lib/active_support/core_ext/benchmark.rb b/activesupport/lib/active_support/core_ext/benchmark.rb
index 2300953860..641b58c8b8 100644
--- a/activesupport/lib/active_support/core_ext/benchmark.rb
+++ b/activesupport/lib/active_support/core_ext/benchmark.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "benchmark"
 
 class << Benchmark
diff --git a/activesupport/lib/active_support/core_ext/big_decimal.rb b/activesupport/lib/active_support/core_ext/big_decimal.rb
index 7b4f87f10e..5568db689b 100644
--- a/activesupport/lib/active_support/core_ext/big_decimal.rb
+++ b/activesupport/lib/active_support/core_ext/big_decimal.rb
@@ -1 +1,3 @@
-require "active_support/core_ext/big_decimal/conversions"
+# frozen_string_literal: true
+
+require_relative "big_decimal/conversions"
diff --git a/activesupport/lib/active_support/core_ext/big_decimal/conversions.rb b/activesupport/lib/active_support/core_ext/big_decimal/conversions.rb
index decd4e1699..52bd229416 100644
--- a/activesupport/lib/active_support/core_ext/big_decimal/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/big_decimal/conversions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "bigdecimal"
 require "bigdecimal/util"
 
diff --git a/activesupport/lib/active_support/core_ext/class.rb b/activesupport/lib/active_support/core_ext/class.rb
index 6a19e862d0..65e1d68399 100644
--- a/activesupport/lib/active_support/core_ext/class.rb
+++ b/activesupport/lib/active_support/core_ext/class.rb
@@ -1,2 +1,4 @@
-require "active_support/core_ext/class/attribute"
-require "active_support/core_ext/class/subclasses"
+# frozen_string_literal: true
+
+require_relative "class/attribute"
+require_relative "class/subclasses"
diff --git a/activesupport/lib/active_support/core_ext/class/attribute.rb b/activesupport/lib/active_support/core_ext/class/attribute.rb
index ba422f9071..a72dbc7bf0 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute.rb
@@ -1,6 +1,8 @@
-require "active_support/core_ext/kernel/singleton_class"
-require "active_support/core_ext/module/remove_method"
-require "active_support/core_ext/array/extract_options"
+# frozen_string_literal: true
+
+require_relative "../kernel/singleton_class"
+require_relative "../module/remove_method"
+require_relative "../array/extract_options"
 
 class Class
   # Declare a class-level attribute whose value is inheritable by subclasses.
@@ -68,11 +70,16 @@ class Class
   #   object.setting = false  # => NoMethodError
   #
   # To opt out of both instance methods, pass <tt>instance_accessor: false</tt>.
+  #
+  # To set a default value for the attribute, pass <tt>default:</tt>, like so:
+  #
+  #   class_attribute :settings, default: {}
   def class_attribute(*attrs)
     options = attrs.extract_options!
-    instance_reader = options.fetch(:instance_accessor, true) && options.fetch(:instance_reader, true)
-    instance_writer = options.fetch(:instance_accessor, true) && options.fetch(:instance_writer, true)
+    instance_reader    = options.fetch(:instance_accessor, true) && options.fetch(:instance_reader, true)
+    instance_writer    = options.fetch(:instance_accessor, true) && options.fetch(:instance_writer, true)
     instance_predicate = options.fetch(:instance_predicate, true)
+    default_value      = options.fetch(:default, nil)
 
     attrs.each do |name|
       remove_possible_singleton_method(name)
@@ -123,6 +130,10 @@ class Class
         remove_possible_method "#{name}="
         attr_writer name
       end
+
+      unless default_value.nil?
+        self.send("#{name}=", default_value)
+      end
     end
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb b/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
index 0f767925ed..b4dbcc6698 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
@@ -1,4 +1,6 @@
+# frozen_string_literal: true
+
 # cattr_* became mattr_* aliases in 7dfbd91b0780fbd6a1dd9bfbc176e10894871d2d,
 # but we keep this around for libraries that directly require it knowing they
 # want cattr_*. No need to deprecate.
-require "active_support/core_ext/module/attribute_accessors"
+require_relative "../module/attribute_accessors"
diff --git a/activesupport/lib/active_support/core_ext/class/subclasses.rb b/activesupport/lib/active_support/core_ext/class/subclasses.rb
index 62397d9508..4c910feb44 100644
--- a/activesupport/lib/active_support/core_ext/class/subclasses.rb
+++ b/activesupport/lib/active_support/core_ext/class/subclasses.rb
@@ -1,5 +1,7 @@
-require "active_support/core_ext/module/anonymous"
-require "active_support/core_ext/module/reachable"
+# frozen_string_literal: true
+
+require_relative "../module/anonymous"
+require_relative "../module/reachable"
 
 class Class
   begin
diff --git a/activesupport/lib/active_support/core_ext/date.rb b/activesupport/lib/active_support/core_ext/date.rb
index 4f66804da2..2a2ed5496f 100644
--- a/activesupport/lib/active_support/core_ext/date.rb
+++ b/activesupport/lib/active_support/core_ext/date.rb
@@ -1,5 +1,7 @@
-require "active_support/core_ext/date/acts_like"
-require "active_support/core_ext/date/blank"
-require "active_support/core_ext/date/calculations"
-require "active_support/core_ext/date/conversions"
-require "active_support/core_ext/date/zones"
+# frozen_string_literal: true
+
+require_relative "date/acts_like"
+require_relative "date/blank"
+require_relative "date/calculations"
+require_relative "date/conversions"
+require_relative "date/zones"
diff --git a/activesupport/lib/active_support/core_ext/date/acts_like.rb b/activesupport/lib/active_support/core_ext/date/acts_like.rb
index 46fe99ad47..81769129b5 100644
--- a/activesupport/lib/active_support/core_ext/date/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/date/acts_like.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/object/acts_like"
+# frozen_string_literal: true
+
+require_relative "../object/acts_like"
 
 class Date
   # Duck-types as a Date-like class. See Object#acts_like?.
diff --git a/activesupport/lib/active_support/core_ext/date/blank.rb b/activesupport/lib/active_support/core_ext/date/blank.rb
index edd2847126..e6271c79b3 100644
--- a/activesupport/lib/active_support/core_ext/date/blank.rb
+++ b/activesupport/lib/active_support/core_ext/date/blank.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "date"
 
 class Date #:nodoc:
diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
index d6f60cac04..1a19ee8b1e 100644
--- a/activesupport/lib/active_support/core_ext/date/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -1,9 +1,11 @@
+# frozen_string_literal: true
+
 require "date"
-require "active_support/duration"
-require "active_support/core_ext/object/acts_like"
-require "active_support/core_ext/date/zones"
-require "active_support/core_ext/time/zones"
-require "active_support/core_ext/date_and_time/calculations"
+require_relative "../../duration"
+require_relative "../object/acts_like"
+require_relative "zones"
+require_relative "../time/zones"
+require_relative "../date_and_time/calculations"
 
 class Date
   include DateAndTime::Calculations
diff --git a/activesupport/lib/active_support/core_ext/date/conversions.rb b/activesupport/lib/active_support/core_ext/date/conversions.rb
index d553406dff..000d6f61ca 100644
--- a/activesupport/lib/active_support/core_ext/date/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/date/conversions.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 require "date"
-require "active_support/inflector/methods"
-require "active_support/core_ext/date/zones"
-require "active_support/core_ext/module/remove_method"
+require_relative "../../inflector/methods"
+require_relative "zones"
+require_relative "../module/remove_method"
 
 class Date
   DATE_FORMATS = {
@@ -79,6 +81,9 @@ class Date
   #   date.to_time(:local)           # => 2007-11-10 00:00:00 0800
   #
   #   date.to_time(:utc)             # => 2007-11-10 00:00:00 UTC
+  #
+  # NOTE: The :local timezone is Ruby's *process* timezone, i.e. ENV['TZ'].
+  #       If the *application's* timezone is needed, then use +in_time_zone+ instead.
   def to_time(form = :local)
     raise ArgumentError, "Expected :local or :utc, got #{form.inspect}." unless [:local, :utc].include?(form)
     ::Time.send(form, year, month, day)
diff --git a/activesupport/lib/active_support/core_ext/date/zones.rb b/activesupport/lib/active_support/core_ext/date/zones.rb
index da23fe4892..1aed070df0 100644
--- a/activesupport/lib/active_support/core_ext/date/zones.rb
+++ b/activesupport/lib/active_support/core_ext/date/zones.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 require "date"
-require "active_support/core_ext/date_and_time/zones"
+require_relative "../date_and_time/zones"
 
 class Date
   include DateAndTime::Zones
diff --git a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
index f2ba7fdda5..8546f7e57b 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/object/try"
+# frozen_string_literal: true
+
+require_relative "../object/try"
 
 module DateAndTime
   module Calculations
@@ -320,6 +322,22 @@ module DateAndTime
       beginning_of_year..end_of_year
     end
 
+    # Returns specific next occurring day of week
+    def next_occurring(day_of_week)
+      current_day_number = wday != 0 ? wday - 1 : 6
+      from_now = DAYS_INTO_WEEK.fetch(day_of_week) - current_day_number
+      from_now += 7 unless from_now > 0
+      since(from_now.days)
+    end
+
+    # Returns specific previous occurring day of week
+    def prev_occurring(day_of_week)
+      current_day_number = wday != 0 ? wday - 1 : 6
+      ago = current_day_number - DAYS_INTO_WEEK.fetch(day_of_week)
+      ago += 7 unless ago > 0
+      ago(ago.days)
+    end
+
     private
       def first_hour(date_or_time)
         date_or_time.acts_like?(:time) ? date_or_time.beginning_of_day : date_or_time
diff --git a/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb b/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
index db95ae0db5..5b3aabf6a5 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/module/attribute_accessors"
+# frozen_string_literal: true
+
+require_relative "../module/attribute_accessors"
 
 module DateAndTime
   module Compatibility
@@ -9,14 +11,6 @@ module DateAndTime
     # of the receiver. For backwards compatibility we're overriding
     # this behavior, but new apps will have an initializer that sets
     # this to true, because the new behavior is preferred.
-    mattr_accessor(:preserve_timezone, instance_writer: false) { false }
-
-    def to_time
-      if preserve_timezone
-        @_to_time_with_instance_offset ||= getlocal(utc_offset)
-      else
-        @_to_time_with_system_offset ||= getlocal
-      end
-    end
+    mattr_accessor :preserve_timezone, instance_writer: false, default: false
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/date_and_time/zones.rb b/activesupport/lib/active_support/core_ext/date_and_time/zones.rb
index edd724f1d0..894fd9b76d 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/zones.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/zones.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module DateAndTime
   module Zones
     # Returns the simultaneous time in <tt>Time.zone</tt> if a zone is given or
diff --git a/activesupport/lib/active_support/core_ext/date_time.rb b/activesupport/lib/active_support/core_ext/date_time.rb
index 6fd498f864..b3d6773e4f 100644
--- a/activesupport/lib/active_support/core_ext/date_time.rb
+++ b/activesupport/lib/active_support/core_ext/date_time.rb
@@ -1,5 +1,7 @@
-require "active_support/core_ext/date_time/acts_like"
-require "active_support/core_ext/date_time/blank"
-require "active_support/core_ext/date_time/calculations"
-require "active_support/core_ext/date_time/compatibility"
-require "active_support/core_ext/date_time/conversions"
+# frozen_string_literal: true
+
+require_relative "date_time/acts_like"
+require_relative "date_time/blank"
+require_relative "date_time/calculations"
+require_relative "date_time/compatibility"
+require_relative "date_time/conversions"
diff --git a/activesupport/lib/active_support/core_ext/date_time/acts_like.rb b/activesupport/lib/active_support/core_ext/date_time/acts_like.rb
index 6f50f55a53..02acb5fe21 100644
--- a/activesupport/lib/active_support/core_ext/date_time/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/acts_like.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 require "date"
-require "active_support/core_ext/object/acts_like"
+require_relative "../object/acts_like"
 
 class DateTime
   # Duck-types as a Date-like class. See Object#acts_like?.
diff --git a/activesupport/lib/active_support/core_ext/date_time/blank.rb b/activesupport/lib/active_support/core_ext/date_time/blank.rb
index b475fd926d..a52c8bc150 100644
--- a/activesupport/lib/active_support/core_ext/date_time/blank.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/blank.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "date"
 
 class DateTime #:nodoc:
diff --git a/activesupport/lib/active_support/core_ext/date_time/calculations.rb b/activesupport/lib/active_support/core_ext/date_time/calculations.rb
index 7a9eb8c266..e61b23f842 100644
--- a/activesupport/lib/active_support/core_ext/date_time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/calculations.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "date"
 
 class DateTime
diff --git a/activesupport/lib/active_support/core_ext/date_time/compatibility.rb b/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
index 30bb7f4a60..71da7be8ca 100644
--- a/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
@@ -1,5 +1,18 @@
-require "active_support/core_ext/date_and_time/compatibility"
+# frozen_string_literal: true
+
+require_relative "../date_and_time/compatibility"
+require_relative "../module/remove_method"
 
 class DateTime
-  prepend DateAndTime::Compatibility
+  include DateAndTime::Compatibility
+
+  remove_possible_method :to_time
+
+  # Either return an instance of `Time` with the same UTC offset
+  # as +self+ or an instance of `Time` representing the same time
+  # in the the local system timezone depending on the setting of
+  # on the setting of +ActiveSupport.to_time_preserves_timezone+.
+  def to_time
+    preserve_timezone ? getlocal(utc_offset) : getlocal
+  end
 end
diff --git a/activesupport/lib/active_support/core_ext/date_time/conversions.rb b/activesupport/lib/active_support/core_ext/date_time/conversions.rb
index d9b3743858..e4c8f9898d 100644
--- a/activesupport/lib/active_support/core_ext/date_time/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/conversions.rb
@@ -1,8 +1,10 @@
+# frozen_string_literal: true
+
 require "date"
-require "active_support/inflector/methods"
-require "active_support/core_ext/time/conversions"
-require "active_support/core_ext/date_time/calculations"
-require "active_support/values/time_zone"
+require_relative "../../inflector/methods"
+require_relative "../time/conversions"
+require_relative "calculations"
+require_relative "../../values/time_zone"
 
 class DateTime
   # Convert to a formatted string. See Time::DATE_FORMATS for predefined formats.
diff --git a/activesupport/lib/active_support/core_ext/digest/uuid.rb b/activesupport/lib/active_support/core_ext/digest/uuid.rb
index e6d60e3267..992e1081e4 100644
--- a/activesupport/lib/active_support/core_ext/digest/uuid.rb
+++ b/activesupport/lib/active_support/core_ext/digest/uuid.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "securerandom"
 
 module Digest
diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index 90d7d2947f..17733d955c 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -1,28 +1,52 @@
+# frozen_string_literal: true
+
 module Enumerable
-  # Calculates a sum from the elements.
-  #
-  #  payments.sum { |p| p.price * p.tax_rate }
-  #  payments.sum(&:price)
-  #
-  # The latter is a shortcut for:
-  #
-  #  payments.inject(0) { |sum, p| sum + p.price }
-  #
-  # It can also calculate the sum without the use of a block.
-  #
-  #  [5, 15, 10].sum # => 30
-  #  ['foo', 'bar'].sum # => "foobar"
-  #  [[1, 2], [3, 1, 5]].sum # => [1, 2, 3, 1, 5]
-  #
-  # The default sum of an empty list is zero. You can override this default:
+  # Enumerable#sum was added in Ruby 2.4, but it only works with Numeric elements
+  # when we omit an identity.
   #
-  #  [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)
-  def sum(identity = nil, &block)
-    if block_given?
-      map(&block).sum(identity)
-    else
-      sum = identity ? inject(identity, :+) : inject(:+)
-      sum || identity || 0
+  # We tried shimming it to attempt the fast native method, rescue TypeError,
+  # and fall back to the compatible implementation, but that's much slower than
+  # just calling the compat method in the first place.
+  if Enumerable.instance_methods(false).include?(:sum) && !((?a..?b).sum rescue false)
+    # We can't use Refinements here because Refinements with Module which will be prepended
+    # doesn't work well https://bugs.ruby-lang.org/issues/13446
+    alias :_original_sum_with_required_identity :sum
+    private :_original_sum_with_required_identity
+    # Calculates a sum from the elements.
+    #
+    #  payments.sum { |p| p.price * p.tax_rate }
+    #  payments.sum(&:price)
+    #
+    # The latter is a shortcut for:
+    #
+    #  payments.inject(0) { |sum, p| sum + p.price }
+    #
+    # It can also calculate the sum without the use of a block.
+    #
+    #  [5, 15, 10].sum # => 30
+    #  ['foo', 'bar'].sum # => "foobar"
+    #  [[1, 2], [3, 1, 5]].sum # => [1, 2, 3, 1, 5]
+    #
+    # The default sum of an empty list is zero. You can override this default:
+    #
+    #  [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)
+    def sum(identity = nil, &block)
+      if identity
+        _original_sum_with_required_identity(identity, &block)
+      elsif block_given?
+        map(&block).sum(identity)
+      else
+        inject(:+) || 0
+      end
+    end
+  else
+    def sum(identity = nil, &block)
+      if block_given?
+        map(&block).sum(identity)
+      else
+        sum = identity ? inject(identity, :+) : inject(:+)
+        sum || identity || 0
+      end
     end
   end
 
diff --git a/activesupport/lib/active_support/core_ext/file.rb b/activesupport/lib/active_support/core_ext/file.rb
index 6d99bad2af..3c2364167d 100644
--- a/activesupport/lib/active_support/core_ext/file.rb
+++ b/activesupport/lib/active_support/core_ext/file.rb
@@ -1 +1,3 @@
-require "active_support/core_ext/file/atomic"
+# frozen_string_literal: true
+
+require_relative "file/atomic"
diff --git a/activesupport/lib/active_support/core_ext/file/atomic.rb b/activesupport/lib/active_support/core_ext/file/atomic.rb
index 8d6c0d3685..8e288833b6 100644
--- a/activesupport/lib/active_support/core_ext/file/atomic.rb
+++ b/activesupport/lib/active_support/core_ext/file/atomic.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "fileutils"
 
 class File
diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index c819307e8a..a74a8c15a6 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -1,9 +1,11 @@
-require "active_support/core_ext/hash/compact"
-require "active_support/core_ext/hash/conversions"
-require "active_support/core_ext/hash/deep_merge"
-require "active_support/core_ext/hash/except"
-require "active_support/core_ext/hash/indifferent_access"
-require "active_support/core_ext/hash/keys"
-require "active_support/core_ext/hash/reverse_merge"
-require "active_support/core_ext/hash/slice"
-require "active_support/core_ext/hash/transform_values"
+# frozen_string_literal: true
+
+require_relative "hash/compact"
+require_relative "hash/conversions"
+require_relative "hash/deep_merge"
+require_relative "hash/except"
+require_relative "hash/indifferent_access"
+require_relative "hash/keys"
+require_relative "hash/reverse_merge"
+require_relative "hash/slice"
+require_relative "hash/transform_values"
diff --git a/activesupport/lib/active_support/core_ext/hash/compact.rb b/activesupport/lib/active_support/core_ext/hash/compact.rb
index e357284be0..d6364dd9f3 100644
--- a/activesupport/lib/active_support/core_ext/hash/compact.rb
+++ b/activesupport/lib/active_support/core_ext/hash/compact.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Hash
   unless Hash.instance_methods(false).include?(:compact)
     # Returns a hash with non +nil+ values.
diff --git a/activesupport/lib/active_support/core_ext/hash/conversions.rb b/activesupport/lib/active_support/core_ext/hash/conversions.rb
index 2a58a7f1ca..0c0701134e 100644
--- a/activesupport/lib/active_support/core_ext/hash/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/hash/conversions.rb
@@ -1,11 +1,13 @@
-require "active_support/xml_mini"
-require "active_support/time"
-require "active_support/core_ext/object/blank"
-require "active_support/core_ext/object/to_param"
-require "active_support/core_ext/object/to_query"
-require "active_support/core_ext/array/wrap"
-require "active_support/core_ext/hash/reverse_merge"
-require "active_support/core_ext/string/inflections"
+# frozen_string_literal: true
+
+require_relative "../../xml_mini"
+require_relative "../../time"
+require_relative "../object/blank"
+require_relative "../object/to_param"
+require_relative "../object/to_query"
+require_relative "../array/wrap"
+require_relative "reverse_merge"
+require_relative "../string/inflections"
 
 class Hash
   # Returns a string containing an XML representation of its receiver:
@@ -71,7 +73,7 @@ class Hash
   # configure your own builder with the <tt>:builder</tt> option. The method also accepts
   # options like <tt>:dasherize</tt> and friends, they are forwarded to the builder.
   def to_xml(options = {})
-    require "active_support/builder" unless defined?(Builder)
+    require_relative "../../builder" unless defined?(Builder)
 
     options = options.dup
     options[:indent]  ||= 2
diff --git a/activesupport/lib/active_support/core_ext/hash/deep_merge.rb b/activesupport/lib/active_support/core_ext/hash/deep_merge.rb
index 9c9faf67ea..f92a2f1c2a 100644
--- a/activesupport/lib/active_support/core_ext/hash/deep_merge.rb
+++ b/activesupport/lib/active_support/core_ext/hash/deep_merge.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Hash
   # Returns a new hash with +self+ and +other_hash+ merged recursively.
   #
diff --git a/activesupport/lib/active_support/core_ext/hash/except.rb b/activesupport/lib/active_support/core_ext/hash/except.rb
index 2f6d38c1f6..6258610c98 100644
--- a/activesupport/lib/active_support/core_ext/hash/except.rb
+++ b/activesupport/lib/active_support/core_ext/hash/except.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Hash
   # Returns a hash that includes everything except given keys.
   #   hash = { a: true, b: false, c: nil }
diff --git a/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb b/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
index 3e1ccecb6c..4681d986db 100644
--- a/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
+++ b/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
@@ -1,4 +1,6 @@
-require "active_support/hash_with_indifferent_access"
+# frozen_string_literal: true
+
+require_relative "../../hash_with_indifferent_access"
 
 class Hash
   # Returns an <tt>ActiveSupport::HashWithIndifferentAccess</tt> out of its receiver:
diff --git a/activesupport/lib/active_support/core_ext/hash/keys.rb b/activesupport/lib/active_support/core_ext/hash/keys.rb
index b7089357a8..d291802b40 100644
--- a/activesupport/lib/active_support/core_ext/hash/keys.rb
+++ b/activesupport/lib/active_support/core_ext/hash/keys.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Hash
   # Returns a new hash with all keys converted using the +block+ operation.
   #
diff --git a/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb b/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb
index bfae57d4be..ef8d592829 100644
--- a/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb
+++ b/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Hash
   # Merges the caller into +other_hash+. For example,
   #
@@ -12,10 +14,12 @@ class Hash
   def reverse_merge(other_hash)
     other_hash.merge(self)
   end
+  alias_method :with_defaults, :reverse_merge
 
   # Destructive +reverse_merge+.
   def reverse_merge!(other_hash)
     replace(reverse_merge(other_hash))
   end
   alias_method :reverse_update, :reverse_merge!
+  alias_method :with_defaults!, :reverse_merge!
 end
diff --git a/activesupport/lib/active_support/core_ext/hash/slice.rb b/activesupport/lib/active_support/core_ext/hash/slice.rb
index 161b00dfb3..94dc225edb 100644
--- a/activesupport/lib/active_support/core_ext/hash/slice.rb
+++ b/activesupport/lib/active_support/core_ext/hash/slice.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Hash
   # Slices a hash to include only the given keys. Returns a hash containing
   # the given keys.
diff --git a/activesupport/lib/active_support/core_ext/hash/transform_values.rb b/activesupport/lib/active_support/core_ext/hash/transform_values.rb
index 2f693bff0c..4b19c9fc1f 100644
--- a/activesupport/lib/active_support/core_ext/hash/transform_values.rb
+++ b/activesupport/lib/active_support/core_ext/hash/transform_values.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Hash
   # Returns a new hash with the results of running +block+ once for every value.
   # The keys are unchanged.
diff --git a/activesupport/lib/active_support/core_ext/integer.rb b/activesupport/lib/active_support/core_ext/integer.rb
index 8f0c55f9d3..df80e7ffdb 100644
--- a/activesupport/lib/active_support/core_ext/integer.rb
+++ b/activesupport/lib/active_support/core_ext/integer.rb
@@ -1,3 +1,5 @@
-require "active_support/core_ext/integer/multiple"
-require "active_support/core_ext/integer/inflections"
-require "active_support/core_ext/integer/time"
+# frozen_string_literal: true
+
+require_relative "integer/multiple"
+require_relative "integer/inflections"
+require_relative "integer/time"
diff --git a/activesupport/lib/active_support/core_ext/integer/inflections.rb b/activesupport/lib/active_support/core_ext/integer/inflections.rb
index bc21b65533..7192e92346 100644
--- a/activesupport/lib/active_support/core_ext/integer/inflections.rb
+++ b/activesupport/lib/active_support/core_ext/integer/inflections.rb
@@ -1,4 +1,6 @@
-require "active_support/inflector"
+# frozen_string_literal: true
+
+require_relative "../../inflector"
 
 class Integer
   # Ordinalize turns a number into an ordinal string used to denote the
diff --git a/activesupport/lib/active_support/core_ext/integer/multiple.rb b/activesupport/lib/active_support/core_ext/integer/multiple.rb
index c668c7c2eb..e7606662d3 100644
--- a/activesupport/lib/active_support/core_ext/integer/multiple.rb
+++ b/activesupport/lib/active_support/core_ext/integer/multiple.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Integer
   # Check whether the integer is evenly divisible by the argument.
   #
diff --git a/activesupport/lib/active_support/core_ext/integer/time.rb b/activesupport/lib/active_support/core_ext/integer/time.rb
index 74baae3639..30c8f3bcf2 100644
--- a/activesupport/lib/active_support/core_ext/integer/time.rb
+++ b/activesupport/lib/active_support/core_ext/integer/time.rb
@@ -1,5 +1,7 @@
-require "active_support/duration"
-require "active_support/core_ext/numeric/time"
+# frozen_string_literal: true
+
+require_relative "../../duration"
+require_relative "../numeric/time"
 
 class Integer
   # Enables the use of time calculations and declarations, like <tt>45.minutes +
diff --git a/activesupport/lib/active_support/core_ext/kernel.rb b/activesupport/lib/active_support/core_ext/kernel.rb
index 3d41ff7876..30810ce315 100644
--- a/activesupport/lib/active_support/core_ext/kernel.rb
+++ b/activesupport/lib/active_support/core_ext/kernel.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/kernel/agnostics"
-require "active_support/core_ext/kernel/concern"
-require "active_support/core_ext/kernel/reporting"
-require "active_support/core_ext/kernel/singleton_class"
+# frozen_string_literal: true
+
+require_relative "kernel/agnostics"
+require_relative "kernel/concern"
+require_relative "kernel/reporting"
+require_relative "kernel/singleton_class"
diff --git a/activesupport/lib/active_support/core_ext/kernel/agnostics.rb b/activesupport/lib/active_support/core_ext/kernel/agnostics.rb
index 64837d87aa..403b5f31f0 100644
--- a/activesupport/lib/active_support/core_ext/kernel/agnostics.rb
+++ b/activesupport/lib/active_support/core_ext/kernel/agnostics.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Object
   # Makes backticks behave (somewhat more) similarly on all platforms.
   # On win32 `nonexistent_command` raises Errno::ENOENT; on Unix, the
diff --git a/activesupport/lib/active_support/core_ext/kernel/concern.rb b/activesupport/lib/active_support/core_ext/kernel/concern.rb
index 307a7f7a63..32af9981a5 100644
--- a/activesupport/lib/active_support/core_ext/kernel/concern.rb
+++ b/activesupport/lib/active_support/core_ext/kernel/concern.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/module/concerning"
+# frozen_string_literal: true
+
+require_relative "../module/concerning"
 
 module Kernel
   module_function
diff --git a/activesupport/lib/active_support/core_ext/kernel/reporting.rb b/activesupport/lib/active_support/core_ext/kernel/reporting.rb
index c02618d5f3..9155bd6c10 100644
--- a/activesupport/lib/active_support/core_ext/kernel/reporting.rb
+++ b/activesupport/lib/active_support/core_ext/kernel/reporting.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Kernel
   module_function
 
diff --git a/activesupport/lib/active_support/core_ext/kernel/singleton_class.rb b/activesupport/lib/active_support/core_ext/kernel/singleton_class.rb
index 9bbf1bbd73..6715eba80a 100644
--- a/activesupport/lib/active_support/core_ext/kernel/singleton_class.rb
+++ b/activesupport/lib/active_support/core_ext/kernel/singleton_class.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Kernel
   # class_eval on an object acts like singleton_class.class_eval.
   def class_eval(*args, &block)
diff --git a/activesupport/lib/active_support/core_ext/load_error.rb b/activesupport/lib/active_support/core_ext/load_error.rb
index d273487010..c3939b5d0b 100644
--- a/activesupport/lib/active_support/core_ext/load_error.rb
+++ b/activesupport/lib/active_support/core_ext/load_error.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class LoadError
   REGEXPS = [
     /^no such file to load -- (.+)$/i,
diff --git a/activesupport/lib/active_support/core_ext/marshal.rb b/activesupport/lib/active_support/core_ext/marshal.rb
index bba2b3be2e..0c72cd7b47 100644
--- a/activesupport/lib/active_support/core_ext/marshal.rb
+++ b/activesupport/lib/active_support/core_ext/marshal.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveSupport
   module MarshalWithAutoloading # :nodoc:
     def load(source, proc = nil)
diff --git a/activesupport/lib/active_support/core_ext/module.rb b/activesupport/lib/active_support/core_ext/module.rb
index 2930255557..da8f572c3b 100644
--- a/activesupport/lib/active_support/core_ext/module.rb
+++ b/activesupport/lib/active_support/core_ext/module.rb
@@ -1,11 +1,13 @@
-require "active_support/core_ext/module/aliasing"
-require "active_support/core_ext/module/introspection"
-require "active_support/core_ext/module/anonymous"
-require "active_support/core_ext/module/reachable"
-require "active_support/core_ext/module/attribute_accessors"
-require "active_support/core_ext/module/attribute_accessors_per_thread"
-require "active_support/core_ext/module/attr_internal"
-require "active_support/core_ext/module/concerning"
-require "active_support/core_ext/module/delegation"
-require "active_support/core_ext/module/deprecation"
-require "active_support/core_ext/module/remove_method"
+# frozen_string_literal: true
+
+require_relative "module/aliasing"
+require_relative "module/introspection"
+require_relative "module/anonymous"
+require_relative "module/reachable"
+require_relative "module/attribute_accessors"
+require_relative "module/attribute_accessors_per_thread"
+require_relative "module/attr_internal"
+require_relative "module/concerning"
+require_relative "module/delegation"
+require_relative "module/deprecation"
+require_relative "module/remove_method"
diff --git a/activesupport/lib/active_support/core_ext/module/aliasing.rb b/activesupport/lib/active_support/core_ext/module/aliasing.rb
index c48bd3354a..6f64d11627 100644
--- a/activesupport/lib/active_support/core_ext/module/aliasing.rb
+++ b/activesupport/lib/active_support/core_ext/module/aliasing.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Module
   # Allows you to make aliases for attributes, which includes
   # getter, setter, and a predicate.
diff --git a/activesupport/lib/active_support/core_ext/module/anonymous.rb b/activesupport/lib/active_support/core_ext/module/anonymous.rb
index 510c9a5430..d1c86b8722 100644
--- a/activesupport/lib/active_support/core_ext/module/anonymous.rb
+++ b/activesupport/lib/active_support/core_ext/module/anonymous.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Module
   # A module may or may not have a name.
   #
diff --git a/activesupport/lib/active_support/core_ext/module/attr_internal.rb b/activesupport/lib/active_support/core_ext/module/attr_internal.rb
index 5081d5f7a3..7801f6d181 100644
--- a/activesupport/lib/active_support/core_ext/module/attr_internal.rb
+++ b/activesupport/lib/active_support/core_ext/module/attr_internal.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Module
   # Declares an attribute reader backed by an internally-named instance variable.
   def attr_internal_reader(*attrs)
diff --git a/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb b/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb
index 2c24081eb9..e667c1f4a4 100644
--- a/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb
+++ b/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb
@@ -1,5 +1,7 @@
-require "active_support/core_ext/array/extract_options"
-require "active_support/core_ext/regexp"
+# frozen_string_literal: true
+
+require_relative "../array/extract_options"
+require_relative "../regexp"
 
 # Extends the module object with class/module and instance accessors for
 # class/module attributes, just like the native attr* accessors for instance
@@ -38,13 +40,10 @@ class Module
   #
   #   Person.new.hair_colors # => NoMethodError
   #
-  #
-  # Also, you can pass a block to set up the attribute with a default value.
+  # You can set a default value for the attribute.
   #
   #   module HairColors
-  #     mattr_reader :hair_colors do
-  #       [:brown, :black, :blonde, :red]
-  #     end
+  #     mattr_reader :hair_colors, default: [:brown, :black, :blonde, :red]
   #   end
   #
   #   class Person
@@ -52,8 +51,7 @@ class Module
   #   end
   #
   #   Person.new.hair_colors # => [:brown, :black, :blonde, :red]
-  def mattr_reader(*syms)
-    options = syms.extract_options!
+  def mattr_reader(*syms, instance_reader: true, instance_accessor: true, default: nil)
     syms.each do |sym|
       raise NameError.new("invalid attribute name: #{sym}") unless /\A[_A-Za-z]\w*\z/.match?(sym)
       class_eval(<<-EOS, __FILE__, __LINE__ + 1)
@@ -64,14 +62,16 @@ class Module
         end
       EOS
 
-      unless options[:instance_reader] == false || options[:instance_accessor] == false
+      if instance_reader && instance_accessor
         class_eval(<<-EOS, __FILE__, __LINE__ + 1)
           def #{sym}
             @@#{sym}
           end
         EOS
       end
-      class_variable_set("@@#{sym}", yield) if block_given?
+
+      sym_default_value = (block_given? && default.nil?) ? yield : default
+      class_variable_set("@@#{sym}", sym_default_value) unless sym_default_value.nil?
     end
   end
   alias :cattr_reader :mattr_reader
@@ -107,12 +107,10 @@ class Module
   #
   #   Person.new.hair_colors = [:blonde, :red] # => NoMethodError
   #
-  # Also, you can pass a block to set up the attribute with a default value.
+  # You can set a default value for the attribute.
   #
   #   module HairColors
-  #     mattr_writer :hair_colors do
-  #       [:brown, :black, :blonde, :red]
-  #     end
+  #     mattr_writer :hair_colors, default: [:brown, :black, :blonde, :red]
   #   end
   #
   #   class Person
@@ -120,8 +118,7 @@ class Module
   #   end
   #
   #   Person.class_variable_get("@@hair_colors") # => [:brown, :black, :blonde, :red]
-  def mattr_writer(*syms)
-    options = syms.extract_options!
+  def mattr_writer(*syms, instance_writer: true, instance_accessor: true, default: nil)
     syms.each do |sym|
       raise NameError.new("invalid attribute name: #{sym}") unless /\A[_A-Za-z]\w*\z/.match?(sym)
       class_eval(<<-EOS, __FILE__, __LINE__ + 1)
@@ -132,14 +129,16 @@ class Module
         end
       EOS
 
-      unless options[:instance_writer] == false || options[:instance_accessor] == false
+      if instance_writer && instance_accessor
         class_eval(<<-EOS, __FILE__, __LINE__ + 1)
           def #{sym}=(obj)
             @@#{sym} = obj
           end
         EOS
       end
-      send("#{sym}=", yield) if block_given?
+
+      sym_default_value = (block_given? && default.nil?) ? yield : default
+      send("#{sym}=", sym_default_value) unless sym_default_value.nil?
     end
   end
   alias :cattr_writer :mattr_writer
@@ -197,12 +196,10 @@ class Module
   #   Person.new.hair_colors = [:brown]  # => NoMethodError
   #   Person.new.hair_colors             # => NoMethodError
   #
-  # Also you can pass a block to set up the attribute with a default value.
+  # You can set a default value for the attribute.
   #
   #   module HairColors
-  #     mattr_accessor :hair_colors do
-  #       [:brown, :black, :blonde, :red]
-  #     end
+  #     mattr_accessor :hair_colors, default: [:brown, :black, :blonde, :red]
   #   end
   #
   #   class Person
@@ -210,9 +207,9 @@ class Module
   #   end
   #
   #   Person.class_variable_get("@@hair_colors") # => [:brown, :black, :blonde, :red]
-  def mattr_accessor(*syms, &blk)
-    mattr_reader(*syms, &blk)
-    mattr_writer(*syms)
+  def mattr_accessor(*syms, instance_reader: true, instance_writer: true, instance_accessor: true, default: nil, &blk)
+    mattr_reader(*syms, instance_reader: instance_reader, instance_accessor: instance_accessor, default: default, &blk)
+    mattr_writer(*syms, instance_writer: instance_writer, instance_accessor: instance_accessor, default: default)
   end
   alias :cattr_accessor :mattr_accessor
 end
diff --git a/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
index 1e82b4acc2..90a350c5dc 100644
--- a/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
+++ b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
@@ -1,5 +1,7 @@
-require "active_support/core_ext/array/extract_options"
-require "active_support/core_ext/regexp"
+# frozen_string_literal: true
+
+require_relative "../array/extract_options"
+require_relative "../regexp"
 
 # Extends the module object with class/module and instance accessors for
 # class/module attributes, just like the native attr* accessors for instance
diff --git a/activesupport/lib/active_support/core_ext/module/concerning.rb b/activesupport/lib/active_support/core_ext/module/concerning.rb
index 97b0a382ce..17c202a24a 100644
--- a/activesupport/lib/active_support/core_ext/module/concerning.rb
+++ b/activesupport/lib/active_support/core_ext/module/concerning.rb
@@ -1,4 +1,6 @@
-require "active_support/concern"
+# frozen_string_literal: true
+
+require_relative "../../concern"
 
 class Module
   # = Bite-sized separation of concerns
diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index cdf27f49ad..6565d53a06 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 require "set"
-require "active_support/core_ext/regexp"
+require_relative "../regexp"
 
 class Module
   # Error generated by +delegate+ when a method is called on +nil+ and +allow_nil+
@@ -174,7 +176,7 @@ class Module
     to = to.to_s
     to = "self.#{to}" if DELEGATION_RESERVED_METHOD_NAMES.include?(to)
 
-    methods.each do |method|
+    methods.map do |method|
       # Attribute writer methods only accept one argument. Makes sure []=
       # methods still accept two arguments.
       definition = /[^\]]=$/.match?(method) ? "arg" : "*args, &block"
@@ -219,55 +221,53 @@ class Module
   # When building decorators, a common pattern may emerge:
   #
   #   class Partition
-  #     def initialize(first_event)
-  #       @events = [ first_event ]
+  #     def initialize(event)
+  #       @event = event
   #     end
   #
-  #     def people
-  #       if @events.first.detail.people.any?
-  #         @events.collect { |e| Array(e.detail.people) }.flatten.uniq
-  #       else
-  #         @events.collect(&:creator).uniq
-  #       end
+  #     def person
+  #       @event.detail.person || @event.creator
   #     end
   #
   #     private
   #       def respond_to_missing?(name, include_private = false)
-  #         @events.respond_to?(name, include_private)
+  #         @event.respond_to?(name, include_private)
   #       end
   #
   #       def method_missing(method, *args, &block)
-  #         @events.send(method, *args, &block)
+  #         @event.send(method, *args, &block)
   #       end
   #   end
   #
-  # With `Module#delegate_missing_to`, the above is condensed to:
+  # With <tt>Module#delegate_missing_to</tt>, the above is condensed to:
   #
   #   class Partition
-  #     delegate_missing_to :@events
+  #     delegate_missing_to :@event
   #
-  #     def initialize(first_event)
-  #       @events = [ first_event ]
+  #     def initialize(event)
+  #       @event = event
   #     end
   #
-  #     def people
-  #       if @events.first.detail.people.any?
-  #         @events.collect { |e| Array(e.detail.people) }.flatten.uniq
-  #       else
-  #         @events.collect(&:creator).uniq
-  #       end
+  #     def person
+  #       @event.detail.person || @event.creator
   #     end
   #   end
   #
-  # The target can be anything callable within the object. E.g. instance
-  # variables, methods, constants and the likes.
+  # The target can be anything callable within the object, e.g. instance
+  # variables, methods, constants, etc.
+  #
+  # The delegated method must be public on the target, otherwise it will
+  # raise +NoMethodError+.
   def delegate_missing_to(target)
     target = target.to_s
     target = "self.#{target}" if DELEGATION_RESERVED_METHOD_NAMES.include?(target)
 
     module_eval <<-RUBY, __FILE__, __LINE__ + 1
       def respond_to_missing?(name, include_private = false)
-        #{target}.respond_to?(name, include_private)
+        # It may look like an oversight, but we deliberately do not pass
+        # +include_private+, because they do not get delegated.
+
+        #{target}.respond_to?(name) || super
       end
 
       def method_missing(method, *args, &block)
diff --git a/activesupport/lib/active_support/core_ext/module/deprecation.rb b/activesupport/lib/active_support/core_ext/module/deprecation.rb
index f3f2e7f5fc..71c42eb357 100644
--- a/activesupport/lib/active_support/core_ext/module/deprecation.rb
+++ b/activesupport/lib/active_support/core_ext/module/deprecation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Module
   #   deprecate :foo
   #   deprecate bar: 'message'
diff --git a/activesupport/lib/active_support/core_ext/module/introspection.rb b/activesupport/lib/active_support/core_ext/module/introspection.rb
index ca20a6d4c5..540385ef6f 100644
--- a/activesupport/lib/active_support/core_ext/module/introspection.rb
+++ b/activesupport/lib/active_support/core_ext/module/introspection.rb
@@ -1,4 +1,6 @@
-require "active_support/inflector"
+# frozen_string_literal: true
+
+require_relative "../../inflector"
 
 class Module
   # Returns the name of the module containing this one.
diff --git a/activesupport/lib/active_support/core_ext/module/reachable.rb b/activesupport/lib/active_support/core_ext/module/reachable.rb
index b89a38f26c..91b230b46c 100644
--- a/activesupport/lib/active_support/core_ext/module/reachable.rb
+++ b/activesupport/lib/active_support/core_ext/module/reachable.rb
@@ -1,5 +1,7 @@
-require "active_support/core_ext/module/anonymous"
-require "active_support/core_ext/string/inflections"
+# frozen_string_literal: true
+
+require_relative "anonymous"
+require_relative "../string/inflections"
 
 class Module
   def reachable? #:nodoc:
diff --git a/activesupport/lib/active_support/core_ext/module/remove_method.rb b/activesupport/lib/active_support/core_ext/module/remove_method.rb
index d5ec16d68a..bf0d686e16 100644
--- a/activesupport/lib/active_support/core_ext/module/remove_method.rb
+++ b/activesupport/lib/active_support/core_ext/module/remove_method.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Module
   # Removes the named method, if it exists.
   def remove_possible_method(method)
diff --git a/activesupport/lib/active_support/core_ext/name_error.rb b/activesupport/lib/active_support/core_ext/name_error.rb
index 6b447d772b..d4f1e01140 100644
--- a/activesupport/lib/active_support/core_ext/name_error.rb
+++ b/activesupport/lib/active_support/core_ext/name_error.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class NameError
   # Extract the name of the missing constant from the exception message.
   #
diff --git a/activesupport/lib/active_support/core_ext/numeric.rb b/activesupport/lib/active_support/core_ext/numeric.rb
index 6062f9e3a8..76e33a7cb0 100644
--- a/activesupport/lib/active_support/core_ext/numeric.rb
+++ b/activesupport/lib/active_support/core_ext/numeric.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/numeric/bytes"
-require "active_support/core_ext/numeric/time"
-require "active_support/core_ext/numeric/inquiry"
-require "active_support/core_ext/numeric/conversions"
+# frozen_string_literal: true
+
+require_relative "numeric/bytes"
+require_relative "numeric/time"
+require_relative "numeric/inquiry"
+require_relative "numeric/conversions"
diff --git a/activesupport/lib/active_support/core_ext/numeric/bytes.rb b/activesupport/lib/active_support/core_ext/numeric/bytes.rb
index dfbca32474..b002eba406 100644
--- a/activesupport/lib/active_support/core_ext/numeric/bytes.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/bytes.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Numeric
   KILOBYTE = 1024
   MEGABYTE = KILOBYTE * 1024
diff --git a/activesupport/lib/active_support/core_ext/numeric/conversions.rb b/activesupport/lib/active_support/core_ext/numeric/conversions.rb
index 4f6621693e..05528f5069 100644
--- a/activesupport/lib/active_support/core_ext/numeric/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/conversions.rb
@@ -1,6 +1,8 @@
-require "active_support/core_ext/big_decimal/conversions"
-require "active_support/number_helper"
-require "active_support/core_ext/module/deprecation"
+# frozen_string_literal: true
+
+require_relative "../big_decimal/conversions"
+require_relative "../../number_helper"
+require_relative "../module/deprecation"
 
 module ActiveSupport::NumericWithFormat
   # Provides options for converting numbers into formatted strings.
diff --git a/activesupport/lib/active_support/core_ext/numeric/inquiry.rb b/activesupport/lib/active_support/core_ext/numeric/inquiry.rb
index ec79701189..15334c91f1 100644
--- a/activesupport/lib/active_support/core_ext/numeric/inquiry.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/inquiry.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 unless 1.respond_to?(:positive?) # TODO: Remove this file when we drop support to ruby < 2.3
   class Numeric
     # Returns true if the number is positive.
diff --git a/activesupport/lib/active_support/core_ext/numeric/time.rb b/activesupport/lib/active_support/core_ext/numeric/time.rb
index 2e6c70d418..0cee87cb86 100644
--- a/activesupport/lib/active_support/core_ext/numeric/time.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/time.rb
@@ -1,8 +1,10 @@
-require "active_support/duration"
-require "active_support/core_ext/time/calculations"
-require "active_support/core_ext/time/acts_like"
-require "active_support/core_ext/date/calculations"
-require "active_support/core_ext/date/acts_like"
+# frozen_string_literal: true
+
+require_relative "../../duration"
+require_relative "../time/calculations"
+require_relative "../time/acts_like"
+require_relative "../date/calculations"
+require_relative "../date/acts_like"
 
 class Numeric
   # Enables the use of time calculations and declarations, like 45.minutes + 2.hours + 4.years.
diff --git a/activesupport/lib/active_support/core_ext/object.rb b/activesupport/lib/active_support/core_ext/object.rb
index 58bbf78601..23f5eec8c7 100644
--- a/activesupport/lib/active_support/core_ext/object.rb
+++ b/activesupport/lib/active_support/core_ext/object.rb
@@ -1,14 +1,16 @@
-require "active_support/core_ext/object/acts_like"
-require "active_support/core_ext/object/blank"
-require "active_support/core_ext/object/duplicable"
-require "active_support/core_ext/object/deep_dup"
-require "active_support/core_ext/object/try"
-require "active_support/core_ext/object/inclusion"
+# frozen_string_literal: true
 
-require "active_support/core_ext/object/conversions"
-require "active_support/core_ext/object/instance_variables"
+require_relative "object/acts_like"
+require_relative "object/blank"
+require_relative "object/duplicable"
+require_relative "object/deep_dup"
+require_relative "object/try"
+require_relative "object/inclusion"
 
-require "active_support/core_ext/object/json"
-require "active_support/core_ext/object/to_param"
-require "active_support/core_ext/object/to_query"
-require "active_support/core_ext/object/with_options"
+require_relative "object/conversions"
+require_relative "object/instance_variables"
+
+require_relative "object/json"
+require_relative "object/to_param"
+require_relative "object/to_query"
+require_relative "object/with_options"
diff --git a/activesupport/lib/active_support/core_ext/object/acts_like.rb b/activesupport/lib/active_support/core_ext/object/acts_like.rb
index 3912cc5ace..2eb72f6b3a 100644
--- a/activesupport/lib/active_support/core_ext/object/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/object/acts_like.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Object
   # A duck-type assistant method. For example, Active Support extends Date
   # to define an <tt>acts_like_date?</tt> method, and extends Time to define
diff --git a/activesupport/lib/active_support/core_ext/object/blank.rb b/activesupport/lib/active_support/core_ext/object/blank.rb
index bdb50ee291..397adbdb5a 100644
--- a/activesupport/lib/active_support/core_ext/object/blank.rb
+++ b/activesupport/lib/active_support/core_ext/object/blank.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/regexp"
+# frozen_string_literal: true
+
+require_relative "../regexp"
 
 class Object
   # An object is blank if it's false, empty, or a whitespace string.
diff --git a/activesupport/lib/active_support/core_ext/object/conversions.rb b/activesupport/lib/active_support/core_ext/object/conversions.rb
index 918ebcdc9f..fdc154188a 100644
--- a/activesupport/lib/active_support/core_ext/object/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/object/conversions.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/object/to_param"
-require "active_support/core_ext/object/to_query"
-require "active_support/core_ext/array/conversions"
-require "active_support/core_ext/hash/conversions"
+# frozen_string_literal: true
+
+require_relative "to_param"
+require_relative "to_query"
+require_relative "../array/conversions"
+require_relative "../hash/conversions"
diff --git a/activesupport/lib/active_support/core_ext/object/deep_dup.rb b/activesupport/lib/active_support/core_ext/object/deep_dup.rb
index 5ac649e552..4021b15de6 100644
--- a/activesupport/lib/active_support/core_ext/object/deep_dup.rb
+++ b/activesupport/lib/active_support/core_ext/object/deep_dup.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/object/duplicable"
+# frozen_string_literal: true
+
+require_relative "duplicable"
 
 class Object
   # Returns a deep copy of object if it's duplicable. If it's
diff --git a/activesupport/lib/active_support/core_ext/object/duplicable.rb b/activesupport/lib/active_support/core_ext/object/duplicable.rb
index ea81df2bd8..1744a44df6 100644
--- a/activesupport/lib/active_support/core_ext/object/duplicable.rb
+++ b/activesupport/lib/active_support/core_ext/object/duplicable.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #--
 # Most objects are cloneable, but not all. For example you can't dup methods:
 #
@@ -106,8 +108,8 @@ require "bigdecimal"
 class BigDecimal
   # BigDecimals are duplicable:
   #
-  # BigDecimal.new("1.2").duplicable? # => true
-  # BigDecimal.new("1.2").dup         # => #<BigDecimal:...,'0.12E1',18(18)>
+  #   BigDecimal.new("1.2").duplicable? # => true
+  #   BigDecimal.new("1.2").dup         # => #<BigDecimal:...,'0.12E1',18(18)>
   def duplicable?
     true
   end
@@ -124,21 +126,31 @@ class Method
 end
 
 class Complex
-  # Complexes are not duplicable:
-  #
-  # Complex(1).duplicable? # => false
-  # Complex(1).dup         # => TypeError: can't copy Complex
-  def duplicable?
-    false
+  begin
+    Complex(1).dup
+  rescue TypeError
+
+    # Complexes are not duplicable:
+    #
+    #   Complex(1).duplicable? # => false
+    #   Complex(1).dup         # => TypeError: can't copy Complex
+    def duplicable?
+      false
+    end
   end
 end
 
 class Rational
-  # Rationals are not duplicable:
-  #
-  # Rational(1).duplicable? # => false
-  # Rational(1).dup         # => TypeError: can't copy Rational
-  def duplicable?
-    false
+  begin
+    Rational(1).dup
+  rescue TypeError
+
+    # Rationals are not duplicable:
+    #
+    #   Rational(1).duplicable? # => false
+    #   Rational(1).dup         # => TypeError: can't copy Rational
+    def duplicable?
+      false
+    end
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/object/inclusion.rb b/activesupport/lib/active_support/core_ext/object/inclusion.rb
index 98bf820d36..6064e92f20 100644
--- a/activesupport/lib/active_support/core_ext/object/inclusion.rb
+++ b/activesupport/lib/active_support/core_ext/object/inclusion.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Object
   # Returns true if this object is included in the argument. Argument must be
   # any object which responds to +#include?+. Usage:
diff --git a/activesupport/lib/active_support/core_ext/object/instance_variables.rb b/activesupport/lib/active_support/core_ext/object/instance_variables.rb
index 593a7a4940..12fdf840b5 100644
--- a/activesupport/lib/active_support/core_ext/object/instance_variables.rb
+++ b/activesupport/lib/active_support/core_ext/object/instance_variables.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Object
   # Returns a hash with string keys that maps instance variable names without "@" to their
   # corresponding values.
diff --git a/activesupport/lib/active_support/core_ext/object/json.rb b/activesupport/lib/active_support/core_ext/object/json.rb
index 1c4d181443..30495313d2 100644
--- a/activesupport/lib/active_support/core_ext/object/json.rb
+++ b/activesupport/lib/active_support/core_ext/object/json.rb
@@ -1,16 +1,18 @@
+# frozen_string_literal: true
+
 # Hack to load json gem first so we can overwrite its to_json.
 require "json"
 require "bigdecimal"
 require "uri/generic"
 require "pathname"
-require "active_support/core_ext/big_decimal/conversions" # for #to_s
-require "active_support/core_ext/hash/except"
-require "active_support/core_ext/hash/slice"
-require "active_support/core_ext/object/instance_variables"
+require_relative "../big_decimal/conversions" # for #to_s
+require_relative "../hash/except"
+require_relative "../hash/slice"
+require_relative "instance_variables"
 require "time"
-require "active_support/core_ext/time/conversions"
-require "active_support/core_ext/date_time/conversions"
-require "active_support/core_ext/date/conversions"
+require_relative "../time/conversions"
+require_relative "../date_time/conversions"
+require_relative "../date/conversions"
 
 # The JSON gem adds a few modules to Ruby core classes containing :to_json definition, overwriting
 # their default behavior. That said, we need to define the basic to_json method in all of them,
diff --git a/activesupport/lib/active_support/core_ext/object/to_param.rb b/activesupport/lib/active_support/core_ext/object/to_param.rb
index 5eeaf03163..c57488bcbc 100644
--- a/activesupport/lib/active_support/core_ext/object/to_param.rb
+++ b/activesupport/lib/active_support/core_ext/object/to_param.rb
@@ -1 +1,3 @@
-require "active_support/core_ext/object/to_query"
+# frozen_string_literal: true
+
+require_relative "to_query"
diff --git a/activesupport/lib/active_support/core_ext/object/to_query.rb b/activesupport/lib/active_support/core_ext/object/to_query.rb
index a3a3abacbb..abb461966a 100644
--- a/activesupport/lib/active_support/core_ext/object/to_query.rb
+++ b/activesupport/lib/active_support/core_ext/object/to_query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cgi"
 
 class Object
diff --git a/activesupport/lib/active_support/core_ext/object/try.rb b/activesupport/lib/active_support/core_ext/object/try.rb
index b2be619b2d..c874691629 100644
--- a/activesupport/lib/active_support/core_ext/object/try.rb
+++ b/activesupport/lib/active_support/core_ext/object/try.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "delegate"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/core_ext/object/with_options.rb b/activesupport/lib/active_support/core_ext/object/with_options.rb
index cf39b1d312..47766f6012 100644
--- a/activesupport/lib/active_support/core_ext/object/with_options.rb
+++ b/activesupport/lib/active_support/core_ext/object/with_options.rb
@@ -1,4 +1,6 @@
-require "active_support/option_merger"
+# frozen_string_literal: true
+
+require_relative "../../option_merger"
 
 class Object
   # An elegant way to factor duplication out of options passed to a series of
@@ -62,6 +64,17 @@ class Object
   #
   # Hence the inherited default for `if` key is ignored.
   #
+  # NOTE: You cannot call class methods implicitly inside of with_options.
+  # You can access these methods using the class name instead:
+  #
+  #   class Phone < ActiveRecord::Base
+  #     enum phone_number_type: [home: 0, office: 1, mobile: 2]
+  #
+  #     with_options presence: true do
+  #       validates :phone_number_type, inclusion: { in: Phone.phone_number_types.keys }
+  #     end
+  #   end
+  #
   def with_options(options, &block)
     option_merger = ActiveSupport::OptionMerger.new(self, options)
     block.arity.zero? ? option_merger.instance_eval(&block) : block.call(option_merger)
diff --git a/activesupport/lib/active_support/core_ext/range.rb b/activesupport/lib/active_support/core_ext/range.rb
index 3190e3ff76..89bbbfcb81 100644
--- a/activesupport/lib/active_support/core_ext/range.rb
+++ b/activesupport/lib/active_support/core_ext/range.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/range/conversions"
-require "active_support/core_ext/range/include_range"
-require "active_support/core_ext/range/overlaps"
-require "active_support/core_ext/range/each"
+# frozen_string_literal: true
+
+require_relative "range/conversions"
+require_relative "range/include_range"
+require_relative "range/overlaps"
+require_relative "range/each"
diff --git a/activesupport/lib/active_support/core_ext/range/conversions.rb b/activesupport/lib/active_support/core_ext/range/conversions.rb
index 69ea046cb6..37868f5875 100644
--- a/activesupport/lib/active_support/core_ext/range/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/range/conversions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveSupport::RangeWithFormat
   RANGE_FORMATS = {
     db: Proc.new { |start, stop| "BETWEEN '#{start.to_s(:db)}' AND '#{stop.to_s(:db)}'" }
diff --git a/activesupport/lib/active_support/core_ext/range/each.rb b/activesupport/lib/active_support/core_ext/range/each.rb
index dc6dad5ced..cdff6393d7 100644
--- a/activesupport/lib/active_support/core_ext/range/each.rb
+++ b/activesupport/lib/active_support/core_ext/range/each.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveSupport
   module EachTimeWithZone #:nodoc:
     def each(&block)
diff --git a/activesupport/lib/active_support/core_ext/range/include_range.rb b/activesupport/lib/active_support/core_ext/range/include_range.rb
index c69e1e3fb9..7ba1011921 100644
--- a/activesupport/lib/active_support/core_ext/range/include_range.rb
+++ b/activesupport/lib/active_support/core_ext/range/include_range.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveSupport
   module IncludeWithRange #:nodoc:
     # Extends the default Range#include? to support range comparisons.
diff --git a/activesupport/lib/active_support/core_ext/range/overlaps.rb b/activesupport/lib/active_support/core_ext/range/overlaps.rb
index 603657c180..f753607f8b 100644
--- a/activesupport/lib/active_support/core_ext/range/overlaps.rb
+++ b/activesupport/lib/active_support/core_ext/range/overlaps.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Range
   # Compare two ranges and see if they overlap each other
   #  (1..5).overlaps?(4..6) # => true
diff --git a/activesupport/lib/active_support/core_ext/regexp.rb b/activesupport/lib/active_support/core_ext/regexp.rb
index d77d01bf42..efbd708aee 100644
--- a/activesupport/lib/active_support/core_ext/regexp.rb
+++ b/activesupport/lib/active_support/core_ext/regexp.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Regexp #:nodoc:
   def multiline?
     options & MULTILINE == MULTILINE
diff --git a/activesupport/lib/active_support/core_ext/securerandom.rb b/activesupport/lib/active_support/core_ext/securerandom.rb
index a57685bea1..b4a491f5fd 100644
--- a/activesupport/lib/active_support/core_ext/securerandom.rb
+++ b/activesupport/lib/active_support/core_ext/securerandom.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "securerandom"
 
 module SecureRandom
diff --git a/activesupport/lib/active_support/core_ext/string.rb b/activesupport/lib/active_support/core_ext/string.rb
index 4cb3200875..491eec2fc9 100644
--- a/activesupport/lib/active_support/core_ext/string.rb
+++ b/activesupport/lib/active_support/core_ext/string.rb
@@ -1,13 +1,15 @@
-require "active_support/core_ext/string/conversions"
-require "active_support/core_ext/string/filters"
-require "active_support/core_ext/string/multibyte"
-require "active_support/core_ext/string/starts_ends_with"
-require "active_support/core_ext/string/inflections"
-require "active_support/core_ext/string/access"
-require "active_support/core_ext/string/behavior"
-require "active_support/core_ext/string/output_safety"
-require "active_support/core_ext/string/exclude"
-require "active_support/core_ext/string/strip"
-require "active_support/core_ext/string/inquiry"
-require "active_support/core_ext/string/indent"
-require "active_support/core_ext/string/zones"
+# frozen_string_literal: true
+
+require_relative "string/conversions"
+require_relative "string/filters"
+require_relative "string/multibyte"
+require_relative "string/starts_ends_with"
+require_relative "string/inflections"
+require_relative "string/access"
+require_relative "string/behavior"
+require_relative "string/output_safety"
+require_relative "string/exclude"
+require_relative "string/strip"
+require_relative "string/inquiry"
+require_relative "string/indent"
+require_relative "string/zones"
diff --git a/activesupport/lib/active_support/core_ext/string/access.rb b/activesupport/lib/active_support/core_ext/string/access.rb
index 6133826f37..58591bbaaf 100644
--- a/activesupport/lib/active_support/core_ext/string/access.rb
+++ b/activesupport/lib/active_support/core_ext/string/access.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class String
   # If you pass a single integer, returns a substring of one character at that
   # position. The first character of the string is at position 0, the next at
diff --git a/activesupport/lib/active_support/core_ext/string/behavior.rb b/activesupport/lib/active_support/core_ext/string/behavior.rb
index 710f1f4670..35a5aa7840 100644
--- a/activesupport/lib/active_support/core_ext/string/behavior.rb
+++ b/activesupport/lib/active_support/core_ext/string/behavior.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class String
   # Enables more predictable duck-typing on String-like classes. See <tt>Object#acts_like?</tt>.
   def acts_like_string?
diff --git a/activesupport/lib/active_support/core_ext/string/conversions.rb b/activesupport/lib/active_support/core_ext/string/conversions.rb
index 221b4969cc..f8f6524b2b 100644
--- a/activesupport/lib/active_support/core_ext/string/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/string/conversions.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 require "date"
-require "active_support/core_ext/time/calculations"
+require_relative "../time/calculations"
 
 class String
   # Converts a string to a Time value.
diff --git a/activesupport/lib/active_support/core_ext/string/exclude.rb b/activesupport/lib/active_support/core_ext/string/exclude.rb
index 0ac684f6ee..8e462689f1 100644
--- a/activesupport/lib/active_support/core_ext/string/exclude.rb
+++ b/activesupport/lib/active_support/core_ext/string/exclude.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class String
   # The inverse of <tt>String#include?</tt>. Returns true if the string
   # does not include the other string.
diff --git a/activesupport/lib/active_support/core_ext/string/filters.rb b/activesupport/lib/active_support/core_ext/string/filters.rb
index a9ec2eb842..66e721eea3 100644
--- a/activesupport/lib/active_support/core_ext/string/filters.rb
+++ b/activesupport/lib/active_support/core_ext/string/filters.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class String
   # Returns the string, first removing all whitespace on both ends of
   # the string, and then changing remaining consecutive whitespace
diff --git a/activesupport/lib/active_support/core_ext/string/indent.rb b/activesupport/lib/active_support/core_ext/string/indent.rb
index d7b58301d3..af9d181487 100644
--- a/activesupport/lib/active_support/core_ext/string/indent.rb
+++ b/activesupport/lib/active_support/core_ext/string/indent.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class String
   # Same as +indent+, except it indents the receiver in-place.
   #
diff --git a/activesupport/lib/active_support/core_ext/string/inflections.rb b/activesupport/lib/active_support/core_ext/string/inflections.rb
index 7a2fc5c1b5..846600c623 100644
--- a/activesupport/lib/active_support/core_ext/string/inflections.rb
+++ b/activesupport/lib/active_support/core_ext/string/inflections.rb
@@ -1,5 +1,7 @@
-require "active_support/inflector/methods"
-require "active_support/inflector/transliterate"
+# frozen_string_literal: true
+
+require_relative "../../inflector/methods"
+require_relative "../../inflector/transliterate"
 
 # String inflections define new methods on the String class to transform names for different purposes.
 # For instance, you can figure out the name of a table from the name of a class.
@@ -100,12 +102,17 @@ class String
   # a nicer looking title. +titleize+ is meant for creating pretty output. It is not
   # used in the Rails internals.
   #
+  # The trailing '_id','Id'.. can be kept and capitalized by setting the
+  # optional parameter +keep_id_suffix+ to true.
+  # By default, this parameter is false.
+  #
   # +titleize+ is also aliased as +titlecase+.
   #
-  #   'man from the boondocks'.titleize # => "Man From The Boondocks"
-  #   'x-men: the last stand'.titleize  # => "X Men: The Last Stand"
-  def titleize
-    ActiveSupport::Inflector.titleize(self)
+  #   'man from the boondocks'.titleize                       # => "Man From The Boondocks"
+  #   'x-men: the last stand'.titleize                        # => "X Men: The Last Stand"
+  #   'string_ending_with_id'.titleize(keep_id_suffix: true)  # => "String Ending With Id"
+  def titleize(keep_id_suffix: false)
+    ActiveSupport::Inflector.titleize(self, keep_id_suffix: keep_id_suffix)
   end
   alias_method :titlecase, :titleize
 
@@ -202,7 +209,7 @@ class String
     ActiveSupport::Inflector.classify(self)
   end
 
-  # Capitalizes the first word, turns underscores into spaces, and strips a
+  # Capitalizes the first word, turns underscores into spaces, and (by default)strips a
   # trailing '_id' if present.
   # Like +titleize+, this is meant for creating pretty output.
   #
@@ -210,12 +217,17 @@ class String
   # optional parameter +capitalize+ to false.
   # By default, this parameter is true.
   #
-  #   'employee_salary'.humanize              # => "Employee salary"
-  #   'author_id'.humanize                    # => "Author"
-  #   'author_id'.humanize(capitalize: false) # => "author"
-  #   '_id'.humanize                          # => "Id"
-  def humanize(options = {})
-    ActiveSupport::Inflector.humanize(self, options)
+  # The trailing '_id' can be kept and capitalized by setting the
+  # optional parameter +keep_id_suffix+ to true.
+  # By default, this parameter is false.
+  #
+  #   'employee_salary'.humanize                    # => "Employee salary"
+  #   'author_id'.humanize                          # => "Author"
+  #   'author_id'.humanize(capitalize: false)       # => "author"
+  #   '_id'.humanize                                # => "Id"
+  #   'author_id'.humanize(keep_id_suffix: true)    # => "Author Id"
+  def humanize(capitalize: true, keep_id_suffix: false)
+    ActiveSupport::Inflector.humanize(self, capitalize: capitalize, keep_id_suffix: keep_id_suffix)
   end
 
   # Converts just the first character to uppercase.
diff --git a/activesupport/lib/active_support/core_ext/string/inquiry.rb b/activesupport/lib/active_support/core_ext/string/inquiry.rb
index c95d83beae..92069981b6 100644
--- a/activesupport/lib/active_support/core_ext/string/inquiry.rb
+++ b/activesupport/lib/active_support/core_ext/string/inquiry.rb
@@ -1,4 +1,6 @@
-require "active_support/string_inquirer"
+# frozen_string_literal: true
+
+require_relative "../../string_inquirer"
 
 class String
   # Wraps the current string in the <tt>ActiveSupport::StringInquirer</tt> class,
diff --git a/activesupport/lib/active_support/core_ext/string/multibyte.rb b/activesupport/lib/active_support/core_ext/string/multibyte.rb
index 1c73182259..fba5b166a2 100644
--- a/activesupport/lib/active_support/core_ext/string/multibyte.rb
+++ b/activesupport/lib/active_support/core_ext/string/multibyte.rb
@@ -1,4 +1,6 @@
-require "active_support/multibyte"
+# frozen_string_literal: true
+
+require_relative "../../multibyte"
 
 class String
   # == Multibyte proxy
diff --git a/activesupport/lib/active_support/core_ext/string/output_safety.rb b/activesupport/lib/active_support/core_ext/string/output_safety.rb
index 94ce3f6a61..adcd2b1dca 100644
--- a/activesupport/lib/active_support/core_ext/string/output_safety.rb
+++ b/activesupport/lib/active_support/core_ext/string/output_safety.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 require "erb"
-require "active_support/core_ext/kernel/singleton_class"
-require "active_support/multibyte/unicode"
+require_relative "../kernel/singleton_class"
+require_relative "../../multibyte/unicode"
 
 class ERB
   module Util
diff --git a/activesupport/lib/active_support/core_ext/string/starts_ends_with.rb b/activesupport/lib/active_support/core_ext/string/starts_ends_with.rb
index 641acf62d0..919eb7a573 100644
--- a/activesupport/lib/active_support/core_ext/string/starts_ends_with.rb
+++ b/activesupport/lib/active_support/core_ext/string/starts_ends_with.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class String
   alias_method :starts_with?, :start_with?
   alias_method :ends_with?, :end_with?
diff --git a/activesupport/lib/active_support/core_ext/string/strip.rb b/activesupport/lib/active_support/core_ext/string/strip.rb
index bb62e6c0ba..cc26274e4a 100644
--- a/activesupport/lib/active_support/core_ext/string/strip.rb
+++ b/activesupport/lib/active_support/core_ext/string/strip.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class String
   # Strips indentation in heredocs.
   #
diff --git a/activesupport/lib/active_support/core_ext/string/zones.rb b/activesupport/lib/active_support/core_ext/string/zones.rb
index de5a28e4f7..db30c03a8e 100644
--- a/activesupport/lib/active_support/core_ext/string/zones.rb
+++ b/activesupport/lib/active_support/core_ext/string/zones.rb
@@ -1,5 +1,7 @@
-require "active_support/core_ext/string/conversions"
-require "active_support/core_ext/time/zones"
+# frozen_string_literal: true
+
+require_relative "conversions"
+require_relative "../time/zones"
 
 class String
   # Converts String to a TimeWithZone in the current zone if Time.zone or Time.zone_default
diff --git a/activesupport/lib/active_support/core_ext/time.rb b/activesupport/lib/active_support/core_ext/time.rb
index b1ae4a45d9..4e16274443 100644
--- a/activesupport/lib/active_support/core_ext/time.rb
+++ b/activesupport/lib/active_support/core_ext/time.rb
@@ -1,5 +1,7 @@
-require "active_support/core_ext/time/acts_like"
-require "active_support/core_ext/time/calculations"
-require "active_support/core_ext/time/compatibility"
-require "active_support/core_ext/time/conversions"
-require "active_support/core_ext/time/zones"
+# frozen_string_literal: true
+
+require_relative "time/acts_like"
+require_relative "time/calculations"
+require_relative "time/compatibility"
+require_relative "time/conversions"
+require_relative "time/zones"
diff --git a/activesupport/lib/active_support/core_ext/time/acts_like.rb b/activesupport/lib/active_support/core_ext/time/acts_like.rb
index cf4b2539c5..309418df42 100644
--- a/activesupport/lib/active_support/core_ext/time/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/time/acts_like.rb
@@ -1,4 +1,6 @@
-require "active_support/core_ext/object/acts_like"
+# frozen_string_literal: true
+
+require_relative "../object/acts_like"
 
 class Time
   # Duck-types as a Time-like class. See Object#acts_like?.
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index 7b7aeef25a..0e51df44ef 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -1,9 +1,11 @@
-require "active_support/duration"
-require "active_support/core_ext/time/conversions"
-require "active_support/time_with_zone"
-require "active_support/core_ext/time/zones"
-require "active_support/core_ext/date_and_time/calculations"
-require "active_support/core_ext/date/calculations"
+# frozen_string_literal: true
+
+require_relative "../../duration"
+require_relative "conversions"
+require_relative "../../time_with_zone"
+require_relative "zones"
+require_relative "../date_and_time/calculations"
+require_relative "../date/calculations"
 
 class Time
   include DateAndTime::Calculations
@@ -107,21 +109,22 @@ class Time
   # to the +options+ parameter. The time options (<tt>:hour</tt>, <tt>:min</tt>,
   # <tt>:sec</tt>, <tt>:usec</tt>, <tt>:nsec</tt>) reset cascadingly, so if only
   # the hour is passed, then minute, sec, usec and nsec is set to 0. If the hour
-  # and minute is passed, then sec, usec and nsec is set to 0. The +options+
-  # parameter takes a hash with any of these keys: <tt>:year</tt>, <tt>:month</tt>,
-  # <tt>:day</tt>, <tt>:hour</tt>, <tt>:min</tt>, <tt>:sec</tt>, <tt>:usec</tt>
-  # <tt>:nsec</tt>. Pass either <tt>:usec</tt> or <tt>:nsec</tt>, not both.
+  # and minute is passed, then sec, usec and nsec is set to 0. The +options+ parameter
+  # takes a hash with any of these keys: <tt>:year</tt>, <tt>:month</tt>, <tt>:day</tt>,
+  # <tt>:hour</tt>, <tt>:min</tt>, <tt>:sec</tt>, <tt>:usec</tt>, <tt>:nsec</tt>,
+  # <tt>:offset</tt>. Pass either <tt>:usec</tt> or <tt>:nsec</tt>, not both.
   #
   #   Time.new(2012, 8, 29, 22, 35, 0).change(day: 1)              # => Time.new(2012, 8, 1, 22, 35, 0)
   #   Time.new(2012, 8, 29, 22, 35, 0).change(year: 1981, day: 1)  # => Time.new(1981, 8, 1, 22, 35, 0)
   #   Time.new(2012, 8, 29, 22, 35, 0).change(year: 1981, hour: 0) # => Time.new(1981, 8, 29, 0, 0, 0)
   def change(options)
-    new_year  = options.fetch(:year, year)
-    new_month = options.fetch(:month, month)
-    new_day   = options.fetch(:day, day)
-    new_hour  = options.fetch(:hour, hour)
-    new_min   = options.fetch(:min, options[:hour] ? 0 : min)
-    new_sec   = options.fetch(:sec, (options[:hour] || options[:min]) ? 0 : sec)
+    new_year   = options.fetch(:year, year)
+    new_month  = options.fetch(:month, month)
+    new_day    = options.fetch(:day, day)
+    new_hour   = options.fetch(:hour, hour)
+    new_min    = options.fetch(:min, options[:hour] ? 0 : min)
+    new_sec    = options.fetch(:sec, (options[:hour] || options[:min]) ? 0 : sec)
+    new_offset = options.fetch(:offset, nil)
 
     if new_nsec = options[:nsec]
       raise ArgumentError, "Can't change both :nsec and :usec at the same time: #{options.inspect}" if options[:usec]
@@ -130,13 +133,18 @@ class Time
       new_usec = options.fetch(:usec, (options[:hour] || options[:min] || options[:sec]) ? 0 : Rational(nsec, 1000))
     end
 
-    if utc?
-      ::Time.utc(new_year, new_month, new_day, new_hour, new_min, new_sec, new_usec)
+    raise ArgumentError, "argument out of range" if new_usec >= 1000000
+
+    new_sec += Rational(new_usec, 1000000)
+
+    if new_offset
+      ::Time.new(new_year, new_month, new_day, new_hour, new_min, new_sec, new_offset)
+    elsif utc?
+      ::Time.utc(new_year, new_month, new_day, new_hour, new_min, new_sec)
     elsif zone
-      ::Time.local(new_year, new_month, new_day, new_hour, new_min, new_sec, new_usec)
+      ::Time.local(new_year, new_month, new_day, new_hour, new_min, new_sec)
     else
-      raise ArgumentError, "argument out of range" if new_usec >= 1000000
-      ::Time.new(new_year, new_month, new_day, new_hour, new_min, new_sec + (new_usec.to_r / 1000000), utc_offset)
+      ::Time.new(new_year, new_month, new_day, new_hour, new_min, new_sec, utc_offset)
     end
   end
 
diff --git a/activesupport/lib/active_support/core_ext/time/compatibility.rb b/activesupport/lib/active_support/core_ext/time/compatibility.rb
index ca4b9574d5..93840e93ca 100644
--- a/activesupport/lib/active_support/core_ext/time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/time/compatibility.rb
@@ -1,5 +1,16 @@
-require "active_support/core_ext/date_and_time/compatibility"
+# frozen_string_literal: true
+
+require_relative "../date_and_time/compatibility"
+require_relative "../module/remove_method"
 
 class Time
-  prepend DateAndTime::Compatibility
+  include DateAndTime::Compatibility
+
+  remove_possible_method :to_time
+
+  # Either return +self+ or the time in the local system timezone depending
+  # on the setting of +ActiveSupport.to_time_preserves_timezone+.
+  def to_time
+    preserve_timezone ? self : getlocal
+  end
 end
diff --git a/activesupport/lib/active_support/core_ext/time/conversions.rb b/activesupport/lib/active_support/core_ext/time/conversions.rb
index 595bda6b4f..e3fc930ef6 100644
--- a/activesupport/lib/active_support/core_ext/time/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/time/conversions.rb
@@ -1,5 +1,7 @@
-require "active_support/inflector/methods"
-require "active_support/values/time_zone"
+# frozen_string_literal: true
+
+require_relative "../../inflector/methods"
+require_relative "../../values/time_zone"
 
 class Time
   DATE_FORMATS = {
diff --git a/activesupport/lib/active_support/core_ext/time/zones.rb b/activesupport/lib/active_support/core_ext/time/zones.rb
index 87b5ad903a..c48edb135f 100644
--- a/activesupport/lib/active_support/core_ext/time/zones.rb
+++ b/activesupport/lib/active_support/core_ext/time/zones.rb
@@ -1,6 +1,8 @@
-require "active_support/time_with_zone"
-require "active_support/core_ext/time/acts_like"
-require "active_support/core_ext/date_and_time/zones"
+# frozen_string_literal: true
+
+require_relative "../../time_with_zone"
+require_relative "acts_like"
+require_relative "../date_and_time/zones"
 
 class Time
   include DateAndTime::Zones
diff --git a/activesupport/lib/active_support/core_ext/uri.rb b/activesupport/lib/active_support/core_ext/uri.rb
index 342a5fcd52..60fc7f084f 100644
--- a/activesupport/lib/active_support/core_ext/uri.rb
+++ b/activesupport/lib/active_support/core_ext/uri.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "uri"
 str = "\xE6\x97\xA5\xE6\x9C\xAC\xE8\xAA\x9E" # Ni-ho-nn-go in UTF-8, means Japanese.
 parser = URI::Parser.new