Add permalink history for taxon on friendly-id

core/app/models/spree/taxon.rb

@@ -4,6 +4,9 @@
 
 module Spree
   class Taxon < Spree::Base
+    extend FriendlyId
+    friendly_id :permalink, use: :history, slug_column: :permalink
+
     acts_as_nested_set dependent: :destroy
 
     belongs_to :taxonomy, class_name: 'Spree::Taxonomy', inverse_of: :taxons
@@ -13,8 +16,7 @@ class Taxon < Spree::Base
     has_many :promotion_rule_taxons
     has_many :promotion_rules, through: :promotion_rule_taxons
 
-    before_create :set_permalink
-    before_update :set_permalink
+    before_save :set_permalink
     after_update :update_child_permalinks, if: :saved_change_to_permalink?
 
     validates :name, presence: true
@@ -121,6 +123,24 @@ def permalink_part=(value)
       end
     end
 
+    # override for {FriendlyId::Slugged#should_generate_new_friendly_id?} method,
+    # to control exactly when new friendly ids are set or updated
+    def should_generate_new_friendly_id?
+      permalink_changed? || super
+    end
+
+    # override for {FriendlyId::Slugged#normalize_friendly_id} method,
+    # to control over the slug format
+    def normalize_friendly_id(value)
+      return '' if value.blank?
+
+      parts = value.to_s.split('/')
+      last_word = parts.pop
+      corrected_last_word = Spree::Config.taxon_url_parametizer_class.parameterize(last_word)
+
+      (parts << corrected_last_word).join('/')
+    end
+
     private
 
     def touch_ancestors_and_taxonomy

core/spec/models/spree/taxon_spec.rb

@@ -269,4 +269,25 @@
       end
     end
   end
+
+  context 'stores history of permalinks' do
+    let!(:parent_taxon) { create(:taxon, name: "brands") }
+    let!(:taxon) { create(:taxon, name: "ruby on rails", parent: parent_taxon) }
+
+    it 'should store the previous slug when permalink is updated' do
+      initial_permalink = taxon.permalink
+
+      expect(taxon.slugs.count).to eq(1)
+      expect(taxon.slugs.last.slug).to eq(initial_permalink)
+
+      taxon.update(permalink: "rails for ruby")
+      updated_permalink = taxon.permalink
+
+      expect(taxon.permalink).to eq(updated_permalink)
+      expect(taxon.slugs.count).to eq(2)
+
+      expect(taxon.slugs.pluck(:slug)).to include(initial_permalink)
+      expect(taxon.slugs.pluck(:slug)).to include(updated_permalink)
+    end
+  end
 end