Better handle API failures

The previous implementation just let the error bubble up. This means
we might loose a sale due to sales tax. Most stores would rather just
pay the sales tax out-of-pocket in these rare events over loosing
a sale.

It might be worth making this an option if there are stores that prefer
to loose the sale but I'll leave it to those stores to implement that.

The system basically treats it as if the order it outside the nexus
(no tax collected) if it cannot contact the API.

To ensure accurate reporting it leaves a log message that is prefixed
with "Taxjar Failure". THe logs should be searched before reporting
sales tax to see if there are any of these.

If a more active notification is desired a log service can be used to
look for that string and send an e-mail to the right person when it
happens.

app/models/spree/taxjar.rb

@@ -28,6 +28,9 @@ def create_transaction_for_order
         Rails.logger.debug order: {id: @order.id, number: @order.number}, api_response: api_response
         api_response
       end
+    rescue HTTP::Error
+      Rails.logger.error "Taxjar Failure: Failed to create transaction for order #{@order.number}"
+      # Silently ignore
     end
 
     def delete_transaction_for_order
@@ -52,6 +55,9 @@ def calculate_tax_for_shipment
       else
         0
       end
+    rescue HTTP::Error
+      Rails.logger.error "Taxjar Failure: Failed to calculate tax for shipment #{@shipment.id} (#{@shipment.order.number})"
+      0
     end
 
     def has_nexus?
@@ -65,6 +71,9 @@ def has_nexus?
       else
         false
       end
+    rescue HTTP::Error
+      Rails.logger.error "Taxjar Failure: Failed to determine nexus for #{@order.number}"
+      false
     end
 
     def calculate_tax_for_order
@@ -76,6 +85,9 @@ def calculate_tax_for_order
         Rails.logger.debug order: {id: @order.id, number: @order.number}, api_response: api_response
         api_response
       end
+    rescue HTTP::Error
+      Rails.logger.error "Taxjar Failure: Failed to calcuate tax for #{@order.number}"
+      nil
     end
 
     private

spec/models/spree/taxjar_spec.rb

@@ -29,6 +29,17 @@
       end
     end
 
+    context 'api is down' do
+      before :each do
+        allow(::Taxjar::Client).to receive(:new).with(api_key: taxjar_api_key).and_return(client)
+        allow( client ).to receive(:nexus_regions).and_raise HTTP::ConnectionError
+      end
+
+      it 'should return true' do
+        expect( spree_taxjar.has_nexus? ).to eq false
+      end
+    end
+
     context 'nexus_regions is present' do
       context 'tax_address is present in nexus regions' do
         it 'should return true' do
@@ -85,6 +96,17 @@
         end
       end
 
+      context 'api is down' do
+        before :each do
+          allow(::Taxjar::Client).to receive(:new).with(api_key: taxjar_api_key).and_return(client)
+          allow( client ).to receive(:nexus_regions).and_raise HTTP::ConnectionError
+        end
+
+        it 'should return nil' do
+          expect(spree_taxjar.create_transaction_for_order).to eq nil
+        end
+      end
+
       context 'when has_nexus? returns true' do
         before do
           allow(::Taxjar::Client).to receive(:new).with(api_key: taxjar_api_key).and_return(client)
@@ -152,6 +174,17 @@
         after { spree_taxjar.calculate_tax_for_order }
 
       end
+
+      context 'api is down' do
+        before :each do
+          allow(::Taxjar::Client).to receive(:new).with(api_key: taxjar_api_key).and_return(client)
+          allow( client ).to receive(:nexus_regions).and_raise HTTP::ConnectionError
+        end
+
+        it 'should return nil' do
+          expect(spree_taxjar.calculate_tax_for_order).to eq nil
+        end
+      end
     end
 
   end