Relation#merge and Relation#except should respect locks

activerecord/lib/active_record/relation/spawn_methods.rb

@@ -24,7 +24,8 @@ def merge(r)
           offset(arel.skipped).
           select(arel.send(:select_clauses)).
           from(arel.sources).
-          having(arel.havings)
+          having(arel.havings).
+          lock(arel.locked)
       end
 
       relation_order = r.send(:order_clause)
@@ -65,6 +66,7 @@ def except(*skips)
       result = result.order(order_clause) unless skips.include?(:order)
       result = result.where(*@relation.wheres) unless skips.include?(:where)
       result = result.having(*@relation.havings) unless skips.include?(:having)
+      result = result.lock(@relation.locked) unless skips.include?(:lock)
 
       result
     end

activerecord/test/cases/relations_test.rb

@@ -407,6 +407,11 @@ def test_relation_merging_with_eager_load
     end
   end
 
+  def test_relation_merging_with_locks
+    devs = Developer.lock.where("salary >= 80000").order("id DESC") & Developer.limit(2)
+    assert devs.locked.present?
+  end
+
   def test_relation_merging_with_preload
     [Post.scoped & Post.preload(:author), Post.preload(:author) & Post.scoped].each do |posts|
       assert_queries(2) { assert posts.first.author }