Revert "Merge pull request #7826 from sikachu/master-validators-kind"

This reverts commit 4e9f53f973, reversing
changes made to 6b802cdb4f.

Revert "Don't use tap in this case."

This reverts commit 454d820bf0.

Reason: Is not a good idea to add options to this method since we can do
the same thing using method composition.

    Person.validators_on(:name).select { |v| v.kind == :presence }

Also it avoids to change the method again to add more options.

activemodel/CHANGELOG.md

@@ -1,15 +1,5 @@
 ## Rails 4.0.0 (unreleased) ##
 
-*   `ActiveModel::Validators#validators_on` now accepts a `:kind` option which will filter out the
-    validators on a particular attribute based on its kind.
-
-        Person.validators_on(:name)
-        # => [#<ActiveModel::Validations::PresenceValidator:0x007fe604914e60 @attributes=[:name], @options={}>,
-        # #<ActiveModel::Validations::InclusionValidator:0x007fe603bb8780 @attributes=[:age], @options={:in=>0..99}>]
-
-        Person.validators_on(:name, kind: :presence)
-        # => [#<ActiveModel::Validations::PresenceValidator:0x007fe604914e60 @attributes=[:name], @options={}>]
-
 *   Add `ActiveModel::ForbiddenAttributesProtection`, a simple module to
     protect attributes from mass assignment when non-permitted attributes are passed.
 

activemodel/lib/active_model/validations.rb

@@ -187,23 +187,10 @@ module ActiveModel
       #   #       #<ActiveModel::Validations::PresenceValidator:0x007fe604914e60 @attributes=[:name], @options={}>,
       #   #       #<ActiveModel::Validations::InclusionValidator:0x007fe603bb8780 @attributes=[:age], @options={:in=>0..99}>
       #   #    ]
-      #
-      # You can also pass a +:kind+ option to filter the validators based on their kind.
-      #
-      #   Person.validators_on(:name, kind: :presence)
-      #   # => [#<ActiveModel::Validations::PresenceValidator:0x007fe604914e60 @attributes=[:name], @options={}>]
       def validators_on(*attributes)
-        options = attributes.extract_options!
+        attributes.map do |attribute|
-
-        validators = attributes.map do |attribute|
           _validators[attribute.to_sym]
         end.flatten
-
-        if options[:kind]
-          validators.select! { |validator| validator.kind == options[:kind] }
-        else
-          validators
-        end
       end
 
       # Returns +true+ if +attribute+ is an attribute method, +false+ otherwise.

activemodel/test/cases/validations_test.rb

@@ -287,14 +287,6 @@ class ValidationsTest < ActiveModel::TestCase
     assert_equal [], Topic.validators_on(:author_name)
   end
 
-  def test_list_of_validators_on_an_attribute_based_on_kind
-    Topic.validates_presence_of :title, :content
-    Topic.validates_length_of :title, :minimum => 2
-
-    assert_equal Topic.validators_on(:title).select { |v| v.kind == :presence },
-      Topic.validators_on(:title, kind: :presence)
-  end
-
   def test_validations_on_the_instance_level
     auto = Automobile.new