updated AMo validations to use a context for valid? and invalid?, removing the dependency on AR

activemodel/lib/active_model/validations.rb

@@ -29,7 +29,7 @@ module ActiveModel
   #   person.invalid?
   #   #=> false
   #   person.first_name = 'zoolander'
-  #   person.valid?         
+  #   person.valid?
   #   #=> false
   #   person.invalid?
   #   #=> true
@@ -48,6 +48,8 @@ module Validations
       extend ActiveModel::Translation
       define_callbacks :validate, :scope => :name
 
+      attr_accessor :validation_context
+
       class_attribute :_validators
       self._validators = Hash.new { |h,k| h[k] = [] }
     end
@@ -117,7 +119,7 @@ def validate(*args, &block)
         options = args.last
         if options.is_a?(Hash) && options.key?(:on)
           options[:if] = Array.wrap(options[:if])
-          options[:if] << "@_on_validate == :#{options[:on]}"
+          options[:if] << "validation_context == :#{options[:on]}"
         end
         set_callback(:validate, *args, &block)
       end
@@ -150,15 +152,20 @@ def errors
     end
 
     # Runs all the specified validations and returns true if no errors were added otherwise false.
-    def valid?
+    # Context can optionally be supplied to define which callbacks to test against (the context is
+    # defined on the validations using :on).
+    def valid?(context = nil)
+      current_context, self.validation_context = validation_context, context
       errors.clear
       _run_validate_callbacks
       errors.empty?
+    ensure
+      self.validation_context = current_context
     end
 
     # Performs the opposite of <tt>valid?</tt>. Returns true if errors were added, false otherwise.
-    def invalid?
-      !valid?
+    def invalid?(context = nil)
+      !valid?(context)
     end
 
     # Hook method defining how an attribute value should be retieved. By default this is assumed