Handle situation where there are no line items

TaxJar API is not keen on orders with no line items and will throw
errors.

2 files changed, 21 insertions, 1 deletions

diff --git a/lib/super_good/solidus_taxjar/tax_calculator.rb b/lib/super_good/solidus_taxjar/tax_calculator.rb
index 474f762..0b02569 100644
--- a/lib/super_good/solidus_taxjar/tax_calculator.rb
+++ b/lib/super_good/solidus_taxjar/tax_calculator.rb
@@ -16,7 +16,7 @@ module SuperGood
       end
 
       def calculate
-        return no_tax if order.tax_address.empty?
+        return no_tax if order.tax_address.empty? || order.line_items.none?
 
         cache do
           next no_tax unless taxjar_breakdown
diff --git a/spec/super_good/solidus_taxjar/tax_calculator_spec.rb b/spec/super_good/solidus_taxjar/tax_calculator_spec.rb
index 87d30c4..b537bfc 100644
--- a/spec/super_good/solidus_taxjar/tax_calculator_spec.rb
+++ b/spec/super_good/solidus_taxjar/tax_calculator_spec.rb
@@ -15,6 +15,7 @@ RSpec.describe ::SuperGood::SolidusTaxJar::TaxCalculator do
         id: 10,
         store: store,
         ship_address: address,
+        line_items: line_items,
         shipments: [
           boring_shipment,
           shipment_with_adjustment,
@@ -23,6 +24,8 @@ RSpec.describe ::SuperGood::SolidusTaxJar::TaxCalculator do
       )
     end
 
+    let(:line_items) { [::Spree::LineItem.new] }
+
     let(:boring_shipment) do
       ::Spree::Shipment.new(id: 1, cost: 7)
     end
@@ -71,6 +74,23 @@ RSpec.describe ::SuperGood::SolidusTaxJar::TaxCalculator do
       end
     end
 
+    context "when the order has no line items" do
+      let(:address) do
+        ::Spree::Address.new(
+          first_name: "Ronnie James",
+          country: ::Spree::Country.new(iso: "US")
+        )
+      end
+
+      let(:line_items) { [] }
+
+      it "returns no taxes" do
+        expect(subject.order_id).to eq order.id
+        expect(subject.shipment_taxes).to be_empty
+        expect(subject.line_item_taxes).to be_empty
+      end
+    end
+
     context "when the API encounters an error" do
       let(:address) do
         ::Spree::Address.new(