From 8104589c0824c648a769be50e04fc8e7dbb26ba0 Mon Sep 17 00:00:00 2001 From: Florian Ebeling Date: Sun, 23 Sep 2018 15:18:57 +0200 Subject: Fix handling of duplicates for `replace` on has_many-through There was a bug in the handling of duplicates when assigning (replacing) associated records, which made the result dependent on whether a given record was associated already before being assigned anew. E.g. post.people = [person, person] post.people.count # => 2 while post.people = [person] post.people = [person, person] post.people.count # => 1 This change adds a test to provoke the former incorrect behavior, and fixes it. Cause of the bug was the handling of record collections as sets, and using `-` (difference) and `&` (union) operations on them indiscriminately. This temporary conversion to sets would eliminate duplicates. The fix is to decorate record collections for these operations, and only for the `has_many :through` case. It is done by counting occurrences, and use the record together with the occurrence number as element, in order to make them work well in sets. Given a, b = *Person.all then the collection used for finding the difference or union of records would be internally changed from [a, b, a] to [[a, 1], [b, 1], [a, 2]] for these operations. So a first occurrence and a second occurrence would be distinguishable, which is all that is necessary for this task. Fixes #33942. --- .../cases/associations/has_many_through_associations_test.rb | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'activerecord/test') diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb index 7b405c74c4..cf514957ca 100644 --- a/activerecord/test/cases/associations/has_many_through_associations_test.rb +++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb @@ -586,6 +586,16 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase assert_not_includes posts(:welcome).reload.people.reload, people(:michael) end + def test_replace_association_with_duplicates + post = posts(:thinking) + person = people(:david) + + assert_difference "post.people.count", 2 do + post.people = [person] + post.people = [person, person] + end + end + def test_replace_order_is_preserved posts(:welcome).people.clear posts(:welcome).people = [people(:david), people(:michael)] -- cgit v1.2.3