Fix `reflection.association_primary_key` for `has_many` associations

It is incorrect to treat `options[:primary_key]` as
`association_primary_key` if `has_many` associations because the
`:primary_key` means the column on the owner record, not on the
association record. It will break `ids_reader` and `ids_writer`.

```ruby
  people(:david).essay_ids
  # => ActiveRecord::StatementInvalid: Mysql2::Error: Unknown column 'essays.first_name' in 'field list': SELECT `essays`.first_name FROM `essays` WHERE `essays`.`writer_id` = 'David'
```

Fixes #14439.

1 files changed, 14 insertions, 3 deletions

diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index cedb621b4f..383c7314e1 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -63,7 +63,7 @@ class HasManyAssociationsTestPrimaryKeys < ActiveRecord::TestCase
       assert_equal 2, subscriber.subscriptions.size
     end
 
-    assert_equal subscriber.subscriptions, Subscription.where(subscriber_id: "webster132")
+    assert_equal Subscription.where(subscriber_id: "webster132"), subscriber.subscriptions
   end
 
   def test_association_primary_key_on_new_record_should_fetch_with_query
@@ -74,12 +74,23 @@ class HasManyAssociationsTestPrimaryKeys < ActiveRecord::TestCase
       assert_equal 1, author.essays.size
     end
 
-    assert_equal author.essays, Essay.where(writer_id: "David")
+    assert_equal Essay.where(writer_id: "David"), author.essays
   end
 
   def test_has_many_custom_primary_key
     david = authors(:david)
-    assert_equal david.essays, Essay.where(writer_id: "David")
+    assert_equal Essay.where(writer_id: "David"), david.essays
+  end
+
+  def test_ids_on_unloaded_association_with_custom_primary_key
+    david = people(:david)
+    assert_equal Essay.where(writer_id: "David").pluck(:id), david.essay_ids
+  end
+
+  def test_ids_on_loaded_association_with_custom_primary_key
+    david = people(:david)
+    david.essays.load
+    assert_equal Essay.where(writer_id: "David").pluck(:id), david.essay_ids
   end
 
   def test_has_many_assignment_with_custom_primary_key