Consider deleted products when creating permalinks

https://github.com/openfoodfoundation/openfoodnetwork/issues/3844

Spree's implementation and our implementation to create a unique
permalink failed to notice conflicts with soft-deleted products. This
patch looks at deleted products as well.

app/models/spree/product_decorator.rb

@@ -252,6 +252,7 @@ Spree::Product.class_eval do
     raise
   end
 
+  # Spree creates a permalink already but our implementation fixes an edge case.
   def sanitize_permalink
     if permalink.blank? || permalink_changed?
       requested = permalink.presence || permalink_was.presence || name.presence || 'product'

lib/open_food_network/permalink_generator.rb

@@ -1,3 +1,10 @@
+# Finds a unique permalink for a new or updated record.
+# It considers soft-deleted records which are ignored by Spree.
+# Spree's work:
+# https://github.com/spree/spree/blob/09b55f7/core/lib/spree/core/permalinks.rb
+#
+# This may become obsolete with Spree 2.3.
+# https://github.com/spree/spree/commits/master/core/lib/spree/core/permalinks.rb
 module PermalinkGenerator
   def self.included(base)
     base.extend(ClassMethods)
@@ -16,7 +23,23 @@ module PermalinkGenerator
   end
 
   def create_unique_permalink(requested)
-    existing = self.class.where('id != ?', id).where("permalink LIKE ?", "#{requested}%").pluck(:permalink)
+    existing = others.where("permalink LIKE ?", "#{requested}%").pluck(:permalink)
     self.class.find_available_value(existing, requested)
   end
+
+  def others
+    if id.nil?
+      scope_with_deleted
+    else
+      scope_with_deleted.where('id != ?', id)
+    end
+  end
+
+  def scope_with_deleted
+    if self.class.respond_to?(:with_deleted)
+      self.class.with_deleted
+    else
+      self.class.scoped
+    end
+  end
 end

spec/models/spree/product_spec.rb

@@ -35,6 +35,25 @@ module Spree
         end
       end
 
+      describe "permalink" do
+        let(:name) { "Banana Permanenta" }
+
+        it "generates a unique permalink" do
+          product1 = create(:product, name: "Banana Permanenta", permalink: nil)
+          product2 = create(:product, name: "Banana Permanenta", permalink: nil)
+          expect(product2.permalink).to_not eq product1.permalink
+          # "banana-permanenta" != "banana-permanenta-1" # generated by Spree
+        end
+
+        it "generates a unique permalink considering deleted products" do
+          product1 = create(:product, name: "Banana Permanenta", permalink: nil)
+          product1.destroy
+          product2 = create(:product, name: "Banana Permanenta", permalink: nil)
+          expect(product2.permalink).to_not eq product1.permalink
+          # "banana-permanenta" != "banana-permanenta1" # generated by OFN
+        end
+      end
+
       describe "tax category" do
         context "when a tax category is required" do
           it "is invalid when a tax category is not provided" do