#422

backend/app/controllers/tag_descriptions_controller.rb

@@ -14,7 +14,7 @@ class TagDescriptionsController < ApplicationController
     render json: representation(description)
   end
 
-  def create
+  def update
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.gte_member?
 
@@ -24,39 +24,23 @@ class TagDescriptionsController < ApplicationController
     tag = Tag.find_by(id: params[:id])
     return head :not_found unless tag
 
-    if TagDescription.exists?(tag:, language_code: 'ja')
+    description = TagDescription.find_by(tag:, language_code: 'ja')
-      return render_unprocessable_entity('説明はすでに存在します．')
+
+    if description
+      TagDescriptionOperation.update!(tag:, body:, updated_by_user: current_user)
+      description.reload
+      render json: representation(description)
+    else
+      TagDescriptionOperation.create!(tag:, body:, created_by_user: current_user)
+      description = TagDescription.find_by!(tag:, language_code: 'ja')
+      render json: representation(description), status: :created
     end
-
-    TagDescriptionOperation.create!(tag:, body:, created_by_user: current_user)
-    description = TagDescription.find_by!(tag:, language_code: 'ja')
-
-    render json: representation(description), status: :created
   rescue ActiveRecord::RecordInvalid => e
     render_validation_error e.record
   rescue ActiveRecord::RecordNotUnique
     render_record_not_unique
   end
 
-  def update
-    return head :unauthorized unless current_user
-    return head :forbidden unless current_user.gte_member?
-
-    body = params[:body].to_s
-    return render_unprocessable_entity('本文は必須です．', field: :body) if body.blank?
-
-    description = TagDescription.find_by(tag_id: params[:id], language_code: 'ja')
-    return create unless description
-
-    TagDescriptionOperation.update!(
-        tag: description.tag, body:, updated_by_user: current_user)
-    description.reload
-
-    render json: representation(description)
-  rescue ActiveRecord::RecordInvalid => e
-    render_validation_error e.record
-  end
-
   private
 
   def representation description

backend/app/controllers/wiki_pages_controller.rb

@@ -2,6 +2,10 @@ class WikiPagesController < ApplicationController
   rescue_from Wiki::Commit::Conflict, with: :render_wiki_conflict
 
   def index
+    # 互換性のための化石リソース
+    # TODO: ヘルプおよびタグ・グループ追加後に，
+    # TODO: タグ説明とヘルプ、タグ・グループから取得する作りに変更する．
+    #
     title = params[:title].to_s.strip
     descriptions = TagDescription.where(language_code: 'ja')
         .includes(tag: :tag_names)

backend/db/migrate/20261005000000_repair_wiki_updated_at.rb

@@ -0,0 +1,53 @@
+class RepairWikiUpdatedAt < ActiveRecord::Migration[8.0]
+  class WikiPage < ActiveRecord::Base
+    self.table_name = 'wiki_pages'
+  end
+
+  class WikiVersion < ActiveRecord::Base
+    self.table_name = 'wiki_versions'
+  end
+
+  class TagDescription < ActiveRecord::Base
+    self.table_name = 'tag_descriptions'
+  end
+
+  class TagDescriptionVersion < ActiveRecord::Base
+    self.table_name = 'tag_description_versions'
+  end
+
+  def up
+    say_with_time 'Repairing wiki_pages.updated_at from wiki_versions' do
+      WikiPage.find_each do |page|
+        version =
+            WikiVersion
+            .where(wiki_page_id: page.id)
+            .order(version_no: :desc)
+            .first
+
+        next unless version
+
+        page.update_columns(updated_at: version.created_at)
+      end
+    end
+
+    say_with_time 'Repairing tag_descriptions.updated_at from tag_description_versions' do
+      TagDescription.find_each do |description|
+        version =
+            TagDescriptionVersion
+            .where(
+                tag_id: description.tag_id,
+                language_code: description.language_code)
+            .order(version_no: :desc)
+            .first
+
+        next unless version
+
+        description.update_columns(updated_at: version.created_at)
+      end
+    end
+  end
+
+  def down
+    ;
+  end
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_10_03_010000) do
+ActiveRecord::Schema[8.0].define(version: 2026_10_05_000000) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false