Variant search: Exclude template variants

Currently, one can add template variants to one's cart, but that should
not be possible. This commit makes sure that the variant search won't
return template variants.

core/lib/spree/core/search/variant.rb

@@ -22,7 +22,7 @@ class Variant
 
         def initialize(query_string, scope: Spree::Variant.all)
           @query_string = query_string
-          @scope = scope
+          @scope = scope.sellable
         end
 
         # Searches the variants table using the ransack 'search_terms' defined on the class.

core/spec/lib/search/variant_spec.rb

@@ -27,6 +27,16 @@ def refute_found(query_string, variant)
       it { refute_found("bca", variant) }
     end
 
+    context "with a template variant" do
+      let!(:option_type) { create(:option_type, option_values: [option_value]) }
+      let(:option_value) { build(:option_value) }
+      let(:product) { create(:product, option_types: [option_type], sku: "TEMPLATE") }
+      let(:variant) { create(:variant, product: product, sku: "NOT_TEMPLATE") }
+
+      it { refute_found("TEMPLATE", product.master) }
+      it { assert_found("NOT_TEMPLATE", variant) }
+    end
+
     context "by product" do
       it { assert_found("My Special Product", variant) }
       it { assert_found("My Spec", variant) }