added the ability not to delete historic slugs when the sluggable class is destroyed

When using acts_as_paranoid on a sluggable models, we aren't actually
deleting the models when calling destroy. If we delete the slugs,
we’re losing the history. We're alsosetting up a condition where a
 unique contstraint may end up being violated

Author: Victor Kmita

lib/friendly_id/base.rb

@@ -187,9 +187,15 @@ module Base
     #   allows an alternate configuration syntax, and conditional configuration
     #   logic.
     #
+    # @option options [Symbol,Boolean] :dependent Available when using `:history`.
+    #   Sets the value used for the slugged association's dependent option. Use
+    #   `false` if you do not want to dependently destroy the associated slugged
+    #   record. Defaults to `:destroy`.
+    #
     # @yieldparam config The model class's {FriendlyId::Configuration friendly_id_config}.
     def friendly_id(base = nil, options = {}, &block)
       yield friendly_id_config if block_given?
+      friendly_id_config.dependent = options.delete :dependent
       friendly_id_config.use options.delete :use
       friendly_id_config.send :set, base ? options.merge(:base => base) : options
       include Model

lib/friendly_id/configuration.rb

@@ -18,6 +18,9 @@ class Configuration
     # The module to use for finders
     attr_accessor :finder_methods
 
+    # The value used for the slugged association's dependent option
+    attr_accessor :dependent
+
     def initialize(model_class, values = nil)
       @model_class    = model_class
       @defaults       = {}

lib/friendly_id/history.rb

@@ -54,9 +54,16 @@ def find_post
 =end
   module History
 
+    module Configuration
+      def dependent_value
+        dependent.nil? ? :destroy : dependent
+      end
+    end
+
     def self.setup(model_class)
       model_class.instance_eval do
         friendly_id_config.use :slugged
+        friendly_id_config.class.send :include, History::Configuration
         friendly_id_config.finder_methods = FriendlyId::History::FinderMethods
         if friendly_id_config.uses? :finders
           relation.class.send(:include, friendly_id_config.finder_methods)
@@ -72,7 +79,7 @@ def self.included(model_class)
       model_class.class_eval do
         has_many :slugs, -> {order("#{Slug.quoted_table_name}.id DESC")}, {
           :as         => :sluggable,
-          :dependent  => :destroy,
+          :dependent  => @friendly_id_config.dependent_value,
           :class_name => Slug.to_s
         }
 

test/history_test.rb

@@ -1,15 +1,15 @@
 require "helper"
 
-class Manual < ActiveRecord::Base
-  extend FriendlyId
-  friendly_id :name, :use => [:slugged, :history]
-end
-
 class HistoryTest < TestCaseClass
 
   include FriendlyId::Test
   include FriendlyId::Test::Shared::Core
 
+  class Manual < ActiveRecord::Base
+    extend FriendlyId
+    friendly_id :name, :use => [:slugged, :history]
+  end
+
   def model_class
     Manual
   end
@@ -172,6 +172,30 @@ def model_class
   end
 end
 
+class DependentDestroyTest < HistoryTest
+
+  include FriendlyId::Test
+
+  class Manual < ActiveRecord::Base
+    extend FriendlyId
+    friendly_id :name, :use => :history, :dependent => false
+  end
+
+  def model_class
+    Manual
+  end
+
+  test "should allow disabling of dependent destroy" do
+    transaction do
+      assert FriendlyId::Slug.find_by_slug('test').nil?
+      l = model_class.create! :name => 'test'
+      assert FriendlyId::Slug.find_by_slug('test').present?
+      l.destroy
+      assert FriendlyId::Slug.find_by_slug('test').present?
+    end
+  end
+end
+
 class HistoryTestWithSti < HistoryTest
   class Journalist < ActiveRecord::Base
     extend FriendlyId