Ensure suppressor runs before validations

I ran into an issue where validations on a suppressed record were
causing validation errors to be thrown on a record that was never going
to be saved.

There isn't a reason to run the validations on a record that doesn't
matter.

This change moves the suppressor up the chain to be run on the `save` or
`save!` in the validations rather than in persistence. The issue with
running it when we hit persistence is that the validations are run
first, then we hit persistance, and then we hit the suppressor. The
suppressor comes first.

The change to the test was required since I added the
`validates_presence_of` validations. Adding this alone was enough to
demonstrate the issue. I added a new test to demonstrate the new
behavior is explict.

activerecord/CHANGELOG.md

@@ -1,3 +1,10 @@
+*   Ensure that the Suppressor runs before validations.
+
+    This moves the suppressor up to be run before validations rather than after
+    validations. There's no reason to validate a record you aren't planning on saving.
+
+    *Eileen M. Uchitelle*
+
 ## Rails 5.0.0.beta3 (February 24, 2016) ##
 
 *   Ensure that mutations of the array returned from `ActiveRecord::Relation#to_a`

activerecord/lib/active_record/suppressor.rb

@@ -37,7 +37,11 @@ def suppress(&block)
       end
     end
 
-    def create_or_update(*args) # :nodoc:
+    def save(*) # :nodoc:
+      SuppressorRegistry.suppressed[self.class.name] ? true : super
+    end
+
+    def save!(*) # :nodoc:
       SuppressorRegistry.suppressed[self.class.name] ? true : super
     end
   end

activerecord/test/cases/suppressor_test.rb

@@ -46,7 +46,18 @@ def test_resumes_saving_after_suppression_complete
     Notification.suppress { UserWithNotification.create! }
 
     assert_difference -> { Notification.count } do
-      Notification.create!
+      Notification.create!(message: "New Comment")
+    end
+  end
+
+  def test_suppresses_validations_on_create
+    assert_no_difference -> { Notification.count } do
+      Notification.suppress do
+        User.create
+        User.create!
+        User.new.save
+        User.new.save!
+      end
     end
   end
 end

activerecord/test/models/notification.rb

@@ -1,2 +1,3 @@
 class Notification < ActiveRecord::Base
+  validates_presence_of :message
 end