Use `Enumerable#sum` on `ActiveRecord::Relation` when a block is given

This matches our behavior in other cases where useful enumerable methods
might have a different definition in `Relation`. Wanting to actually
enumerate over the records in this case is completely reasonable, and
wanting `.sum` is reasonable for the same reason it is on `Enumerable`
in the first place.

1 files changed, 6 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 7a28a98721..29cc79db1b 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -70,8 +70,12 @@ module ActiveRecord
     # +calculate+ for examples with options.
     #
     #   Person.sum(:age) # => 4562
-    def sum(*args)
-      calculate(:sum, *args)
+    def sum(*args, &block)
+      if block_given?
+        to_a.sum(&block)
+      else
+        calculate(:sum, *args)
+      end
     end
 
     # This calculates aggregate values in the given column. Methods for count, sum, average,