rm cached attributes

The original patch that added this concept can be found
[here](https://web.archive.org/web/20090601022739/http://dev.rubyonrails.org/ticket/9767).
The current default behavior is to cache everything except serialized
columns, unless the user specified otherwise. If anyone were to specify
otherwise, many types would actually be completely broken. Still, the
method is left in place with a deprecation warning in case anyone is
actually still calling this method.

3 files changed, 24 insertions, 73 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 7839f7544b..8e958a851e 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Remove `cache_attributes` and friends. All attributes are cached.
+
+    *Sean Griffin*
+
 *   Remove deprecated method `ActiveRecord::Base.quoted_locking_column`.
 
     *Akshay Vishnoi*
diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
index a354cd7503..7b7e37884b 100644
--- a/activerecord/lib/active_record/attribute_methods/read.rb
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -35,35 +35,22 @@ module ActiveRecord
 
       extend ActiveSupport::Concern
 
-      ATTRIBUTE_TYPES_CACHED_BY_DEFAULT = [:datetime, :time, :date]
-
-      included do
-        class_attribute :attribute_types_cached_by_default, instance_writer: false
-        self.attribute_types_cached_by_default = ATTRIBUTE_TYPES_CACHED_BY_DEFAULT
-      end
-
       module ClassMethods
-        # +cache_attributes+ allows you to declare which converted attribute
-        # values should be cached. Usually caching only pays off for attributes
-        # with expensive conversion methods, like time related columns (e.g.
-        # +created_at+, +updated_at+).
-        def cache_attributes(*attribute_names)
-          cached_attributes.merge attribute_names.map { |attr| attr.to_s }
+        [:cache_attributes, :cached_attributes, :cache_attribute?].each do |method_name|
+          define_method method_name do |*|
+            cached_attributes_deprecation_warning(method_name)
+            true
+          end
         end
 
-        # Returns the attributes which are cached. By default time related columns
-        # with datatype <tt>:datetime, :time, :date</tt> are cached.
-        def cached_attributes
-          @cached_attributes ||= columns.select { |c| cacheable_column?(c) }.map { |col| col.name }.to_set
-        end
+        protected
 
-        # Returns +true+ if the provided attribute is being cached.
-        def cache_attribute?(attr_name)
-          cached_attributes.include?(attr_name)
+        def cached_attributes_deprecation_warning(method_name)
+          ActiveSupport::Deprecation.warn(<<-MESSAGE.strip_heredoc)
+            Calling `#{method_name}` is no longer necessary. All attributes are cached.
+          MESSAGE
         end
 
-        protected
-
         if Module.methods_transplantable?
           def define_method_attribute(name)
             method = ReaderMethodCache[name]
@@ -89,16 +76,6 @@ module ActiveRecord
             end
           end
         end
-
-        private
-
-        def cacheable_column?(column)
-          if attribute_types_cached_by_default == ATTRIBUTE_TYPES_CACHED_BY_DEFAULT
-            true
-          else
-            attribute_types_cached_by_default.include?(column.type)
-          end
-        end
       end
 
       # Returns the value of the attribute identified by <tt>attr_name</tt> after
@@ -122,11 +99,7 @@ module ActiveRecord
             return block_given? ? yield(name) : nil
           }
 
-          if self.class.cache_attribute?(name)
-            @attributes[name] = column.type_cast_from_database(value)
-          else
-            column.type_cast_from_database value
-          end
+          @attributes[name] = column.type_cast_from_database(value)
         }
       end
 
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 139fe9c04b..a366caf875 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -517,43 +517,17 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     end
   end
 
-  def test_only_time_related_columns_are_meant_to_be_cached_by_default
-    expected = %w(datetime time date).sort
-    assert_equal expected, ActiveRecord::Base.attribute_types_cached_by_default.map(&:to_s).sort
-  end
-
-  def test_declaring_attributes_as_cached_adds_them_to_the_attributes_cached_by_default
-    default_attributes = Topic.cached_attributes
-    Topic.cache_attributes :replies_count
-    expected = default_attributes + ["replies_count"]
-    assert_equal expected.sort, Topic.cached_attributes.sort
-    Topic.instance_variable_set "@cached_attributes", nil
-  end
-
-  def test_cacheable_columns_are_actually_cached
-    assert_equal cached_columns.sort, Topic.cached_attributes.sort
-  end
-
-  def test_accessing_cached_attributes_caches_the_converted_values_and_nothing_else
-    t = topics(:first)
-    cache = t.instance_variable_get "@attributes"
-
-    assert_not_nil cache
-    assert cache.empty?
+  def test_deprecated_cache_attributes
+    assert_deprecated do
+      Topic.cache_attributes :replies_count
+    end
 
-    all_columns = Topic.columns.map(&:name)
-    uncached_columns = all_columns - cached_columns
+    assert_deprecated do
+      Topic.cached_attributes
+    end
 
-    all_columns.each do |attr_name|
-      attribute_gets_cached = Topic.cache_attribute?(attr_name)
-      val = t.send attr_name unless attr_name == "type"
-      if attribute_gets_cached
-        assert cached_columns.include?(attr_name)
-        assert_equal val, cache[attr_name]
-      else
-        assert uncached_columns.include?(attr_name)
-        assert !cache.include?(attr_name)
-      end
+    assert_deprecated do
+      Topic.cache_attribute? :replies_count
     end
   end