#281

backend/app/models/tag.rb

@@ -162,14 +162,18 @@ class Tag < ApplicationRecord
         end
 
         source_tag_name = source_tag.tag_name
-        nico_flg = source_tag.nico?
-        source_tag.discard!
-        source_tag_name.reload
 
-        if nico_flg
-          source_tag_name.destroy!
+        if source_tag_name.wiki_page.present?
+          raise ActiveRecord::RecordInvalid.new(source_tag_name)
+        end
+
+        source_tag.discard!
+
+        if source_tag.nico?
+          source_tag_name.discard!
         else
-          source_tag_name.update!(canonical: target_tag.tag_name)
+          source_tag_name.update_columns(canonical_id: target_tag.tag_name_id,
+                                         updated_at: Time.current)
         end
       end
 

backend/app/models/tag_name.rb

@@ -1,4 +1,8 @@
 class TagName < ApplicationRecord
+  include Discard::Model
+
+  default_scope -> { kept }
+
   has_one :tag
   has_one :wiki_page
 

backend/app/models/tag_name_sanitisation_rule.rb

@@ -24,12 +24,15 @@ class TagNameSanitisationRule < ApplicationRecord
             existing_tn = existing_tn.canonical || existing_tn
             next if existing_tn.id == tn.id
 
-            if existing_tn.tag
-              Tag.merge_tags!(existing_tn.tag, tn.tag) if tn.tag
-            elsif tn.tag
-              tn.tag.update_columns(tag_name_id: existing_tn.id, updated_at: Time.current)
+            existing_tag = Tag.find_by(tag_name_id: existing_tn.id)
+            source_tag = Tag.find_by(tag_name_id: tn.id)
+
+            if existing_tag
+              Tag.merge_tags!(existing_tag, source_tag) if tn.tag
+            elsif source_tag
+              source_tag.update_columns(tag_name_id: existing_tn.id, updated_at: Time.current)
             end
-            tn.destroy!
+            tn.discard!
 
             next
           end

backend/app/models/wiki_page.rb

@@ -2,6 +2,10 @@ require 'set'
 
 
 class WikiPage < ApplicationRecord
+  include Discard::Model
+
+  default_scope -> { kept }
+
   has_many :wiki_revisions, dependent: :destroy
   belongs_to :created_user, class_name: 'User'
   belongs_to :updated_user, class_name: 'User'