Merge pull request #47565 from Shopify/fix-nullifying-association-wit…

…h-composite-query-constraints

Fix nullifying association with composite query constraints

activerecord/lib/active_record/associations/foreign_association.rb

@@ -12,7 +12,7 @@ def foreign_key_present?
 
     def nullified_owner_attributes
       Hash.new.tap do |attrs|
-        attrs[reflection.foreign_key] = nil
+        Array(reflection.foreign_key).each { |foreign_key| attrs[foreign_key] = nil }
         attrs[reflection.type] = nil if reflection.type.present?
       end
     end

activerecord/test/cases/associations_test.rb

@@ -177,6 +177,21 @@ def test_append_composite_foreign_key_has_many_association
     assert_equal(blog_post.blog_id, comment.blog_id)
   end
 
+  def test_nullify_composite_foreign_key_has_many_association
+    blog_post = sharded_blog_posts(:great_post_blog_one)
+    comment = sharded_comments(:great_comment_blog_post_one)
+
+    assert_not_empty(blog_post.comments)
+    blog_post.comments = []
+
+    comment = Sharded::Comment.find(comment.id)
+    assert_nil(comment.blog_post_id)
+    assert_nil(comment.blog_id)
+
+    assert_empty(blog_post.comments)
+    assert_empty(blog_post.reload.comments)
+  end
+
   def test_assign_persisted_composite_foreign_key_belongs_to_association
     comment = sharded_comments(:great_comment_blog_post_one)
     another_blog = sharded_blogs(:sharded_blog_two)
@@ -192,6 +207,19 @@ def test_assign_persisted_composite_foreign_key_belongs_to_association
     assert_equal(comment.blog_post_id, blog_post.id)
   end
 
+  def test_nullify_composite_foreign_key_belongs_to_association
+    comment = sharded_comments(:great_comment_blog_post_one)
+    assert_not_nil(comment.blog_post)
+
+    comment.blog_post = nil
+    assert_nil(comment.blog_id)
+    assert_nil(comment.blog_post_id)
+
+    comment.save
+    assert_nil(comment.blog_post)
+    assert_nil(comment.reload.blog_post)
+  end
+
   def test_assign_composite_foreign_key_belongs_to_association
     comment = sharded_comments(:great_comment_blog_post_one)
     another_blog = sharded_blogs(:sharded_blog_two)