Handle errors gracefully

3 files changed, 66 insertions, 6 deletions

diff --git a/README.md b/README.md
index ad11782..3e2c0a7 100644
--- a/README.md
+++ b/README.md
@@ -6,15 +6,39 @@ This is not a fork of [spree_taxjar](https://github.com/vinsol-spree-contrib/spr
 
 ## Installation
 
-Add this line to your application's Gemfile:
+1. Add this line to your application's Gemfile:
 
-```ruby
-gem 'super_good-solidus_taxjar'
-```
+   ```ruby
+   gem 'super_good-solidus_taxjar'
+   ```
 
-And then execute:
+   And then execute:
 
-    $ bundle
+       $ bundle
+
+2. Next, configure Solidus to use this gem:
+
+   ```ruby
+   # Put this in config/initializers/solidus.rb
+
+   Spree.config do |config|
+     config.tax_calculator_class = SuperGood::SolidusTaxJar::TaxCalculator
+   end
+   ```
+
+3. Also, configure your error handling:
+
+   ```ruby
+   # Put this in config/initializers/taxjar.rb
+
+   SuperGood::SolidusTaxJar::TaxCalculator.exception_handler = ->(e) {
+     # Report exceptions in here. For example, if you were using the Sentry's
+     # raven-ruby gem to report errors, you might do this:
+     Raven.capture_exception(exception)
+   }
+   ```
+
+4. Finally, make sure that the `TAXJAR_API_KEY` environment variable is set to a your TaxJar API key and make sure that you have a `Spree::TaxRate` with the name "Sales Tax". This will be used as the source for the tax adjustments that Solidus creates.
 
 ## Development
 
diff --git a/lib/super_good/solidus_taxjar/tax_calculator.rb b/lib/super_good/solidus_taxjar/tax_calculator.rb
index d683cf6..474f762 100644
--- a/lib/super_good/solidus_taxjar/tax_calculator.rb
+++ b/lib/super_good/solidus_taxjar/tax_calculator.rb
@@ -1,6 +1,11 @@
 module SuperGood
   module SolidusTaxJar
     class TaxCalculator
+      class_attribute :exception_handler
+      self.exception_handler = ->(e) {
+        Rails.logger.error "An error occurred while fetching TaxJar tax rates - #{e}: #{e.message}"
+      }
+
       def self.default_api
         ::SuperGood::SolidusTaxJar::API.new
       end
@@ -22,6 +27,9 @@ module SuperGood
             shipment_taxes: shipment_taxes
           )
         end
+      rescue StandardError => e
+        exception_handler.(e)
+        no_tax
       end
 
       private
diff --git a/spec/super_good/solidus_taxjar/tax_calculator_spec.rb b/spec/super_good/solidus_taxjar/tax_calculator_spec.rb
index 875f428..87d30c4 100644
--- a/spec/super_good/solidus_taxjar/tax_calculator_spec.rb
+++ b/spec/super_good/solidus_taxjar/tax_calculator_spec.rb
@@ -71,6 +71,34 @@ RSpec.describe ::SuperGood::SolidusTaxJar::TaxCalculator do
       end
     end
 
+    context "when the API encounters an error" do
+      let(:address) do
+        ::Spree::Address.new(
+          first_name: "Ronnie James",
+          country: ::Spree::Country.new(iso: "US")
+        )
+      end
+
+      before do
+        allow(dummy_api).to receive(:tax_for).with(order).and_raise("A bad thing happened.")
+      end
+
+      it "calls the configured error handler" do
+        expect(described_class.exception_handler).to receive(:call) do |e|
+          expect(e).to be_a StandardError
+          expect(e.message).to eq "A bad thing happened."
+        end
+
+        subject
+      end
+
+      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 order has a non-empty tax address" do
       let(:address) do
         ::Spree::Address.new(