Prevent loops

app/assets/javascripts/tags.js

@@ -15,8 +15,9 @@ $(() => {
 
   const template = (tag) => {
     const tagSpan = `<span>${tag.text}</span>`;
+    let desc = !!tag.desc ? splitWordsMaxLength(tag.desc, 120) : '';
     const descSpan = !!tag.desc ?
-      `<br/><span class="has-color-tertiary-900 has-font-size-caption">${splitWordsMaxLength(tag.desc, 120)[0]}...</span>` :
+      `<br/><span class="has-color-tertiary-900 has-font-size-caption">${desc[0]}${desc.length > 1 ? '...' : ''}</span>` :
       '';
     return $(tagSpan + descSpan);
   }

app/models/tag.rb

@@ -8,6 +8,7 @@ class Tag < ApplicationRecord
 
   validates :excerpt, length: { maximum: 600 }, allow_blank: true
   validates :wiki_markdown, length: { maximum: 30000 }, allow_blank: true
+  validate :parent_not_own_child
 
   def self.search(term)
     where('name LIKE ?', "%#{sanitize_sql_like(term)}%")
@@ -19,4 +20,13 @@ class Tag < ApplicationRecord
     query = query.gsub('$ParentId', id.to_s)
     ActiveRecord::Base.connection.execute(query).to_a.map(&:first)
   end
+
+  private
+
+  def parent_not_own_child
+    return unless parent_id.present?
+    if all_children.include? parent_id
+      errors.add(:base, "The #{parent.name} tag is already a child of this tag.")
+    end
+  end
 end