Handle missing master price when adding a variant

backend/app/controllers/spree/admin/variants_controller.rb

@@ -16,7 +16,9 @@ def new_before
         @object.attributes = @object.product.master.attributes.except("id", "created_at", "deleted_at",
           "sku", "is_master")
         # Shallow Clone of the default price to populate the price field.
-        @object.prices.build(@object.product.master.default_price.attributes.except("id", "created_at", "updated_at", "deleted_at"))
+        if (default_price = @object.product.master.default_price)
+          @object.prices.build(default_price.attributes.except("id", "created_at", "updated_at", "deleted_at"))
+        end
       end
 
       def collection

backend/spec/controllers/spree/admin/variants_controller_spec.rb

@@ -7,6 +7,42 @@ module Admin
     describe VariantsController, type: :controller do
       stub_authorization!
 
+      describe "#new" do
+        render_views
+
+        let(:product) { create(:product_with_option_types) }
+
+        before do
+          create(:option_value, option_type: product.option_types.first)
+        end
+
+        subject { get :new, params: {product_id: product.slug} }
+
+        it "builds a variant with the master default price" do
+          subject
+
+          expect(response).to be_successful
+          expect(assigns(:variant).default_price.amount).to eq(product.master.default_price.amount)
+        end
+
+        context "when the product has no master default price" do
+          before do
+            product.master.prices.delete_all
+          end
+
+          it "builds a variant with a new default price" do
+            subject
+
+            default_price = assigns(:variant).default_price
+
+            expect(response).to be_successful
+            expect(default_price).to be_new_record
+            expect(default_price.amount).to be_nil
+            expect(default_price.currency).to eq(Spree::Config[:currency])
+          end
+        end
+      end
+
       describe "#index" do
         let(:product) { create(:product) }
         let(:params) { {product_id: product.slug} }