1 files changed, 80 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/validations/confirmation.rb b/activemodel/lib/active_model/validations/confirmation.rb
new file mode 100644
index 0000000000..b549755ba4
--- /dev/null
+++ b/activemodel/lib/active_model/validations/confirmation.rb
@@ -0,0 +1,80 @@
+# frozen_string_literal: true
+
+module ActiveModel
+  module Validations
+    class ConfirmationValidator < EachValidator # :nodoc:
+      def initialize(options)
+        super({ case_sensitive: true }.merge!(options))
+        setup!(options[:class])
+      end
+
+      def validate_each(record, attribute, value)
+        unless (confirmed = record.send("#{attribute}_confirmation")).nil?
+          unless confirmation_value_equal?(record, attribute, value, confirmed)
+            human_attribute_name = record.class.human_attribute_name(attribute)
+            record.errors.add(:"#{attribute}_confirmation", :confirmation, options.except(:case_sensitive).merge!(attribute: human_attribute_name))
+          end
+        end
+      end
+
+      private
+        def setup!(klass)
+          klass.attr_reader(*attributes.map do |attribute|
+            :"#{attribute}_confirmation" unless klass.method_defined?(:"#{attribute}_confirmation")
+          end.compact)
+
+          klass.attr_writer(*attributes.map do |attribute|
+            :"#{attribute}_confirmation" unless klass.method_defined?(:"#{attribute}_confirmation=")
+          end.compact)
+        end
+
+        def confirmation_value_equal?(record, attribute, value, confirmed)
+          if !options[:case_sensitive] && value.is_a?(String)
+            value.casecmp(confirmed) == 0
+          else
+            value == confirmed
+          end
+        end
+    end
+
+    module HelperMethods
+      # Encapsulates the pattern of wanting to validate a password or email
+      # address field with a confirmation.
+      #
+      #   Model:
+      #     class Person < ActiveRecord::Base
+      #       validates_confirmation_of :user_name, :password
+      #       validates_confirmation_of :email_address,
+      #                                 message: 'should match confirmation'
+      #     end
+      #
+      #   View:
+      #     <%= password_field "person", "password" %>
+      #     <%= password_field "person", "password_confirmation" %>
+      #
+      # The added +password_confirmation+ attribute is virtual; it exists only
+      # as an in-memory attribute for validating the password. To achieve this,
+      # the validation adds accessors to the model for the confirmation
+      # attribute.
+      #
+      # NOTE: This check is performed only if +password_confirmation+ is not
+      # +nil+. To require confirmation, make sure to add a presence check for
+      # the confirmation attribute:
+      #
+      #   validates_presence_of :password_confirmation, if: :password_changed?
+      #
+      # Configuration options:
+      # * <tt>:message</tt> - A custom error message (default is: "doesn't match
+      #   <tt>%{translated_attribute_name}</tt>").
+      # * <tt>:case_sensitive</tt> - Looks for an exact match. Ignored by
+      #   non-text columns (+true+ by default).
+      #
+      # There is also a list of default options supported by every validator:
+      # +:if+, +:unless+, +:on+, +:allow_nil+, +:allow_blank+, and +:strict+.
+      # See <tt>ActiveModel::Validations#validates</tt> for more information
+      def validates_confirmation_of(*attr_names)
+        validates_with ConfirmationValidator, _merge_attributes(attr_names)
+      end
+    end
+  end
+end