Allow assignment on has_one :through where the owner is a new record [#5137 state:resolved]

This required changing the code to keep the association proxy for a belongs_to around, despite its target being nil. Which in turn required various changes to the way that stale target checking is handled, in order to support various edge cases (loaded target is nil then foreign key added, foreign key is changed and then changed back, etc). A side effect is that the code is nicer and more succinct.

Note that I am removing test_no_unexpected_aliasing since that is basically checking that the proxy for a belongs_to *does* change, which is the exact opposite of the intention of this commit. Also adding various tests for various edge cases and related things.

Phew, long commit message!

1 files changed, 1 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/associations/has_one_through_association.rb b/activerecord/lib/active_record/associations/has_one_through_association.rb
index c9ae930e93..11fa40a5c4 100644
--- a/activerecord/lib/active_record/associations/has_one_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_through_association.rb
@@ -7,6 +7,7 @@ module ActiveRecord
       def replace(new_value)
         create_through_record(new_value)
         @target = new_value
+        loaded
       end
 
       private
@@ -32,7 +33,6 @@ module ActiveRecord
       end
 
       def find_target
-        update_stale_state
         scoped.first
       end
     end