Rase when calling `lock!` in a dirty record

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Raises when calling `lock!` in a dirty record.
+
+    *Rafael Mendonça França*
+
 *   Remove deprecated support to passing a class to `:class_name` on associations.
 
     *Rafael Mendonça França*

activerecord/lib/active_record/locking/pessimistic.rb

@@ -63,12 +63,13 @@ module Pessimistic
       def lock!(lock = true)
         if persisted?
           if changed?
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Locking a record with unpersisted changes is deprecated and will raise an
-              exception in Rails 5.2. Use `save` to persist the changes, or `reload` to
-              discard them explicitly.
+            raise(<<-MSG.squish)
+              Locking a record with unpersisted changes is not supported. Use
+              `save` to persist the changes, or `reload` to discard them
+              explicitly.
             MSG
           end
+
           reload(lock: lock)
         end
         self

activerecord/test/cases/locking_test.rb

@@ -565,18 +565,18 @@ def test_eager_find_with_lock
       end
     end
 
-    # Locking a record reloads it.
-    def test_sane_lock_method
+    def test_lock_does_not_raise_when_the_object_is_not_dirty
+      person = Person.find 1
       assert_nothing_raised do
-        Person.transaction do
-          person = Person.find 1
-          old, person.first_name = person.first_name, "fooman"
-          # Locking a dirty record is deprecated
-          assert_deprecated do
-            person.lock!
-          end
-          assert_equal old, person.first_name
-        end
+        person.lock!
+      end
+    end
+
+    def test_lock_raises_when_the_record_is_dirty
+      person = Person.find 1
+      person.first_name = "fooman"
+      assert_raises(RuntimeError) do
+        person.lock!
       end
     end