Deprecate Relation#sum with a block.

To perform a sum calculation over the array of elements, use to_a.sum(&block).

Please check the discussion in f9cb645dfcb5cc89f59d2f8b58a019486c828c73
for more context.

2 files changed, 10 insertions, 2 deletions

diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 01afa087be..6cdc166533 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -1658,6 +1658,12 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_deprecated { klass.has_many :foo, :counter_sql => 'lol' }
   end
 
+  test "sum calculation with block for array compatibility is deprecated" do
+    assert_deprecated do
+      posts(:welcome).comments.sum { |c| c.id }
+    end
+  end
+
   test "has many associations on new records use null relations" do
     post = Post.new
 
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index bf8c0f1e70..5cb7eabf0e 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -389,8 +389,10 @@ class CalculationsTest < ActiveRecord::TestCase
         Account.where("credit_limit > 50").from('accounts').sum(:credit_limit)
   end
 
-  def test_sum_array_compatibility
-    assert_equal Account.sum(:credit_limit), Account.sum(&:credit_limit)
+  def test_sum_array_compatibility_deprecation
+    assert_deprecated do
+      assert_equal Account.sum(:credit_limit), Account.sum(&:credit_limit)
+    end
   end
 
   def test_average_with_from_option