Merge branch 'master' into adequaterecord

* master: (70 commits)
  [ci skip] Added link to ruby-lang.org installation.
  Use the index on hidden field
  `collection_check_boxes` respects `:index` option for the hidden filed name.
  docs, double meaning of `serialize` argument. Closes #14284.
  Just call read_attribute, no need to use `send`.
  - Fix lingering reference to `:text` instead of the newer `:plain` - Section references `form_tag` instead of the `form_for` used in the example
  again, read_attribute is public, so just call it
  read_attribute is public, so we should just call it
  Disable assest cache store in docs [ci skip]
  Make counter cache decrementation on destroy idempotent
  Write the failing test case for concurrent counter cache
  [ci skip] Use plain underscore instead of "\_".
  Update documentation to use Rails.application instead
  Add a changelog entry for #14546 [ci skip]
  Move tests for deep_dup and duplicable to object directory
  Missing 'are' in note - [ci skip]
  CollectionHelpers now accepts a readonly option
  Fix a few typos [ci skip]
  Bundle tzinfo-data on :x64_mingw (64-bit Ruby on Windows).
  don't bother with an offset if the offset is zero
  ...

1 files changed, 16 insertions, 5 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/serialization.rb b/activerecord/lib/active_record/attribute_methods/serialization.rb
index 67abbbc2a0..c3466153d6 100644
--- a/activerecord/lib/active_record/attribute_methods/serialization.rb
+++ b/activerecord/lib/active_record/attribute_methods/serialization.rb
@@ -30,7 +30,8 @@ module ActiveRecord
         # ==== Parameters
         #
         # * +attr_name+ - The field name that should be serialized.
-        # * +class_name+ - Optional, class name that the object type should be equal to.
+        # * +class_name_or_coder+ - Optional, a coder object, which responds to `.load` / `.dump`
+        #   or a class name that the object type should be equal to.
         #
         # ==== Example
         #
@@ -38,13 +39,23 @@ module ActiveRecord
         #   class User < ActiveRecord::Base
         #     serialize :preferences
         #   end
-        def serialize(attr_name, class_name = Object)
+        #
+        #   # Serialize preferences using JSON as coder.
+        #   class User < ActiveRecord::Base
+        #     serialize :preferences, JSON
+        #   end
+        #
+        #   # Serialize preferences as Hash using YAML coder.
+        #   class User < ActiveRecord::Base
+        #     serialize :preferences, Hash
+        #   end
+        def serialize(attr_name, class_name_or_coder = Object)
           include Behavior
 
-          coder = if [:load, :dump].all? { |x| class_name.respond_to?(x) }
-                    class_name
+          coder = if [:load, :dump].all? { |x| class_name_or_coder.respond_to?(x) }
+                    class_name_or_coder
                   else
-                    Coders::YAMLColumn.new(class_name)
+                    Coders::YAMLColumn.new(class_name_or_coder)
                   end
 
           # merge new serialized attribute and create new hash to ensure that each class in inheritance hierarchy