Make NullRelation a bit more like a real relation by returning 0 for #calculate(:count)

2 files changed, 8 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/null_relation.rb b/activerecord/lib/active_record/null_relation.rb
index 5d801fa705..d166f0dd66 100644
--- a/activerecord/lib/active_record/null_relation.rb
+++ b/activerecord/lib/active_record/null_relation.rb
@@ -55,7 +55,11 @@ module ActiveRecord
     end
 
     def calculate(_operation, _column_name, _options = {})
-      nil
+      if _operation == :count
+        0
+      else
+        nil
+      end
     end
 
     def exists?(_id = false)
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index cf6af4e8f4..2ab5231458 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -278,8 +278,9 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_null_relation_calculations_methods
     assert_no_queries do
-      assert_equal 0,     Developer.none.count
-      assert_equal nil,   Developer.none.calculate(:average, 'salary')
+      assert_equal 0, Developer.none.count
+      assert_equal 0, Developer.none.calculate(:count, nil, {})
+      assert_equal nil, Developer.none.calculate(:average, 'salary')
     end
   end