WIP: Building migration to duplicate master variants

db/migrate/20141003060622_add_standard_variant_to_products.rb

@@ -0,0 +1,49 @@
+class AddStandardVariantToProducts < ActiveRecord::Migration
+  def change
+    # Find products without any standard variants
+    products_with_only_master = Spree::Product.where( variants: [] )
+
+
+    products_with_only_master.each do |product|
+      # Run the callback to add a copy of the master variant as a standard variant
+      product.send(:ensure_standard_variant)
+
+      existing_master = product.master
+      new_variant = product.variants.first
+
+      # Replace any existing references to the master variant with the new standard variant
+
+      # Option Values
+      # Strategy: add all option values on existing_master to new_variant, and keep on existing_master
+      option_values = existing_master.option_values
+      option_values.each do |option_value|
+        variant_ids = option_value.variant_ids
+        variant_ids << new_variant.id
+        option_value.update_attributes(variant_ids: variant_ids)
+      end
+
+      # Inventory Units
+      # Strategy: completely replace all references to existing_master with new_variant
+      inventory_units = existing_master.inventory_units
+      inventory_units.each do |inventory_unit|
+        inventory_unit.update_attributes(variant_id: new_variant.id )
+      end
+
+      # Line Items
+      # Strategy: completely replace all references to existing_master with new_variant
+      line_items = existing_master.line_items
+      line_items.each do |line_item|
+        line_item.update_attributes(variant_id: new_variant.id )
+      end
+
+      # Prices
+      # Strategy: duplicate all prices on existing_master and assign them to new_variant
+      prices = existing_master.prices
+      new_prices = []
+      prices.each do |price|
+        new_prices << price.dup
+      end
+      new_variant.update_attributes(prices: new_prices)
+    end
+  end
+end