Improve Checkout error handling in JS

app/assets/javascripts/darkswarm/services/checkout.js.coffee

@@ -14,15 +14,28 @@ Darkswarm.factory 'Checkout', ($injector, CurrentOrder, ShippingMethods, StripeE
 
     submit: =>
       Loading.message = t 'submitting_order'
-      $http.put('/checkout.json', {order: @preprocess()}).success (data, status)=>
-        Navigation.go data.path
-      .error (response, status)=>
-        if response.path
-          Navigation.go response.path
-        else
-          Loading.clear()
-          @errors = response.errors
-          RailsFlashLoader.loadFlash(response.flash)
+      $http.put('/checkout.json', {order: @preprocess()})
+      .then (response) =>
+        Navigation.go response.data.path
+      .catch (response) =>
+        try
+          @handle_checkout_error_response(response)
+        catch error
+          @loadFlash(error: t("checkout.failed")) # inform the user about the unexpected error
+          throw error # generate a BugsnagJS alert
+
+    handle_checkout_error_response: (response) =>
+      if response.data.path
+        Navigation.go response.data.path
+      else
+        throw response unless response.data.flash
+
+        @errors = response.data.errors
+        @loadFlash(response.data.flash)
+
+    loadFlash: (flash) =>
+      Loading.clear()
+      RailsFlashLoader.loadFlash(flash)
 
     # Rails wants our Spree::Address data to be provided with _attributes
     preprocess: ->

spec/javascripts/unit/darkswarm/services/checkout_spec.js.coffee

@@ -3,10 +3,13 @@ describe 'Checkout service', ->
   orderData = null
   $httpBackend = null
   Navigation = null
+  navigationSpy = null
   flash = null
   scope = null
   FlashLoaderMock =
-    loadFlash: (arg)->
+    loadFlash: (arg) ->
+  Loading =
+    clear: (arg)->
   paymentMethods = [{
       id: 99
       test: "foo"
@@ -48,6 +51,7 @@ describe 'Checkout service', ->
     module 'Darkswarm'
     module ($provide)->
       $provide.value "RailsFlashLoader", FlashLoaderMock
+      $provide.value "Loading", Loading
       $provide.value "currentOrder", orderData
       $provide.value "shippingMethods", shippingMethods
       $provide.value "paymentMethods", paymentMethods
@@ -61,7 +65,7 @@ describe 'Checkout service', ->
       scope.Checkout = Checkout
       Navigation = $injector.get("Navigation")
       flash = $injector.get("flash")
-      spyOn(Navigation, "go") # Stubbing out writes to window.location
+      navigationSpy = spyOn(Navigation, "go") # Stubbing out writes to window.location
 
   it "defaults to no shipping method", ->
     expect(Checkout.order.shipping_method_id).toEqual null
@@ -116,12 +120,46 @@ describe 'Checkout service', ->
         $httpBackend.flush()
         expect(FlashLoaderMock.loadFlash).toHaveBeenCalledWith {error: "frogs"}
 
-      it "puts errors into the scope", ->
-        $httpBackend.expectPUT("/checkout.json").respond 400, {errors: {error: "frogs"}}
+      it "puts errors into the scope when there is a flash messages", ->
+        $httpBackend.expectPUT("/checkout.json").respond 400, {errors: {error: "frogs"}, flash: {error: "flash frogs"}}
         Checkout.submit()
+
         $httpBackend.flush()
         expect(Checkout.errors).toEqual {error: "frogs"}
 
+      it "throws exception and sends generic flash message when there are errors but no flash message", ->
+        $httpBackend.expectPUT("/checkout.json").respond 400, {errors: {error: "broken response"}}
+        try
+          Checkout.submit()
+          $httpBackend.flush()
+        catch error
+          expect(error.data.errors.error).toBe("broken response")
+
+        expect(Checkout.errors).toEqual {}
+
+      it "throws an exception and sends a flash message to the flash service when reponse doesnt contain errors nor a flash message", ->
+        spyOn(FlashLoaderMock, "loadFlash") # Stubbing out writes to window.location
+        $httpBackend.expectPUT("/checkout.json").respond 400, "broken response"
+        try
+          Checkout.submit()
+          $httpBackend.flush()
+        catch error
+          expect(error.data).toBe("broken response")
+
+        expect(FlashLoaderMock.loadFlash).toHaveBeenCalledWith({ error: t("checkout.failed") })
+
+      it "throws an exception and sends a flash message to the flash service when an exception is thrown while handling the error", ->
+        spyOn(FlashLoaderMock, "loadFlash") # Stubbing out writes to window.location
+        navigationSpy.and.callFake(-> throw "unexpected error")
+        $httpBackend.expectPUT("/checkout.json").respond 400, {path: 'path'}
+        try
+          Checkout.submit()
+          $httpBackend.flush()
+        catch error
+          expect(error).toBe("unexpected error")
+
+        expect(FlashLoaderMock.loadFlash).toHaveBeenCalledWith({ error: t("checkout.failed") })
+
     describe "when using the Stripe Connect gateway", ->
       beforeEach inject ($injector, StripeElements) ->
         Checkout.order.payment_method_id = 666