#55 いったん中断；外部タグ分離優先

backend/app/models/tag.rb

@@ -242,12 +242,14 @@ class Tag < ApplicationRecord
     end
 
     tag = tn.tag
-    unless tag
-      tag = Tag.find_undiscard_or_create_by!(tag_name_id: tn.id) do
-        _1.category = category
-      end
+    if tag
+      tag.update!(tag_name_id: tn.id) if tag.tag_name_id != tn.id
+      return tag
     end
 
+    tag = Tag.create!(tag_name: tn, category:)
+    tn.update!(tag:)
+
     tag
   rescue ActiveRecord::RecordNotUnique
     retry

backend/app/models/tag_name.rb

@@ -1,5 +1,5 @@
 class TagName < ApplicationRecord
-  belongs_to :tag
+  belongs_to :tag, optional: true
   has_one :wiki_page
 
   belongs_to :canonical, class_name: 'TagName', optional: true