Avoid sending 0 quantity line items

3 files changed, 66 insertions, 2 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 50c2d0c..7d842a3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## master
 
+- Avoid sending 0 quantity line items. TaxJar doesn't like them.
+
 ## v0.10.0
 
 - Make shipping amounts configurable to make it easier to support order-level adjustments.
diff --git a/lib/super_good/solidus_taxjar/api_params.rb b/lib/super_good/solidus_taxjar/api_params.rb
index 8596856..25f8317 100644
--- a/lib/super_good/solidus_taxjar/api_params.rb
+++ b/lib/super_good/solidus_taxjar/api_params.rb
@@ -63,7 +63,7 @@ module SuperGood
 
         def line_items_params(line_items)
           {
-            line_items: line_items.map do |line_item|
+            line_items: valid_line_items(line_items).map do |line_item|
               {
                 id: line_item.id,
                 quantity: line_item.quantity,
@@ -77,7 +77,7 @@ module SuperGood
 
         def transaction_line_items_params(line_items)
           {
-            line_items: line_items.map do |line_item|
+            line_items: valid_line_items(line_items).map do |line_item|
               {
                 id: line_item.id,
                 quantity: line_item.quantity,
@@ -91,6 +91,14 @@ module SuperGood
           }
         end
 
+        def valid_line_items(line_items)
+          # The API appears to error when sent line items with no quantity...
+          # but why would you do that anyway.
+          line_items.reject do |line_item|
+            line_item.quantity.zero?
+          end
+        end
+
         def discount(line_item)
           ::SuperGood::SolidusTaxJar.discount_calculator.new(line_item).discount
         end
diff --git a/spec/super_good/solidus_taxjar/api_params_spec.rb b/spec/super_good/solidus_taxjar/api_params_spec.rb
index 3688d2f..9c8696f 100644
--- a/spec/super_good/solidus_taxjar/api_params_spec.rb
+++ b/spec/super_good/solidus_taxjar/api_params_spec.rb
@@ -140,6 +140,32 @@ RSpec.describe SuperGood::SolidusTaxJar::APIParams do
         }]
       )
     end
+
+    context "when the line item has zero quantity" do
+      let(:line_item) do
+        Spree::LineItem.new(
+          variant: variant,
+          price: 10,
+          quantity: 0,
+          promo_total: -2,
+          additional_tax_total: 4
+        )
+      end
+
+      it "excludes the line item" do
+        expect(subject).to eq(
+          to_country: "US",
+          to_zip: "90210",
+          to_city: "Los Angeles",
+          to_state: "CA",
+          to_street: "475 N Beverly Dr",
+
+          shipping: 3.01,
+
+          line_items: []
+        )
+      end
+    end
   end
 
   describe "#address_params" do
@@ -184,6 +210,34 @@ RSpec.describe SuperGood::SolidusTaxJar::APIParams do
        }]
       })
     end
+
+    context "when the line item has 0 quantity" do
+      let(:line_item) do
+        Spree::LineItem.new(
+          variant: variant,
+          price: 10,
+          quantity: 0,
+          promo_total: -2,
+          additional_tax_total: 4
+        )
+      end
+
+      it "excludes the line item" do
+        expect(subject).to eq({
+         amount: BigDecimal("113.58"),
+         sales_tax: BigDecimal("9.87"),
+         shipping: BigDecimal("3.01"),
+         to_city: "Los Angeles",
+         to_country: "US",
+         to_state: "CA",
+         to_street: "475 N Beverly Dr",
+         to_zip: "90210",
+         transaction_date: "2018-03-06T12:10:33Z",
+         transaction_id: "R111222333",
+         line_items: []
+        })
+      end
+    end
   end
 
   describe "#refund_params" do