Allow multiple subcategories with the same name

app/models/category.rb

@@ -23,7 +23,7 @@ class Category < ActiveRecord::Base
   has_many :groups, through: :category_groups
 
   validates :user_id, presence: true
-  validates :name, presence: true, uniqueness: true, length: { in: 1..50 }
+  validates :name, presence: true, uniqueness: { scope: :parent_category_id }, length: { in: 1..50 }
   validate :parent_category_validator
 
   before_validation :ensure_slug
@@ -161,7 +161,7 @@ SQL
     t = Topic.new(title: I18n.t("category.topic_prefix", category: name), user: user, pinned_at: Time.now, category_id: id)
     t.skip_callbacks = true
     t.auto_close_hours = nil
-    t.save!
+    t.save!(validate: false)
     update_column(:topic_id, t.id)
     t.posts.create(raw: post_template, user: user)
   end

db/migrate/20140526185749_change_category_uniquness_contstraint.rb

@@ -0,0 +1,6 @@
+class ChangeCategoryUniqunessContstraint < ActiveRecord::Migration
+  def change
+    remove_index :categories, name: 'index_categories_on_name'
+    add_index :categories, [:parent_category_id, :name], unique: true
+  end
+end

spec/models/category_spec.rb

@@ -9,7 +9,7 @@ describe Category do
 
   it 'validates uniqueness of name' do
     Fabricate(:category)
-    should validate_uniqueness_of(:name)
+    should validate_uniqueness_of(:name).scoped_to(:parent_category_id)
   end
 
   it { should belong_to :topic }