Respond with errors if image upload fails

app/controllers/api/v0/product_images_controller.rb

@@ -16,9 +16,12 @@ module Api
 
         success_status = image.persisted? ? :ok : :created
 
-        image.update(attachment: params[:file])
-
-        render json: image, serializer: ImageSerializer, status: success_status
+        if image.update(attachment: params[:file])
+          render json: image, serializer: ImageSerializer, status: success_status
+        else
+          error_json = { errors: image.errors.full_messages }
+          render json: error_json, status: :unprocessable_entity
+        end
       end
     end
   end

spec/controllers/api/v0/product_images_controller_spec.rb

@@ -9,6 +9,8 @@ describe Api::V0::ProductImagesController, type: :controller do
 
   describe "uploading an image" do
     let(:image) { Rack::Test::UploadedFile.new(black_logo_file, 'image/png') }
+    let(:pdf) { Rack::Test::UploadedFile.new(pdf_path, 'application/pdf') }
+    let(:pdf_path) { Rails.root.join("public/Terms-of-service.pdf") }
     let(:product_without_image) { create(:product) }
     let(:product_with_image) { create(:product_with_image) }
     let(:current_api_user) { create(:admin_user) }
@@ -34,5 +36,16 @@ describe Api::V0::ProductImagesController, type: :controller do
       expect(response.status).to eq 200
       expect(product_with_image.images.first.id).to eq json_response['id']
     end
+
+    it "reports errors when saving fails" do
+      post :update_product_image, xhr: true, params: {
+        product_id: product_without_image.id, file: pdf, use_route: :product_images
+      }
+
+      expect(response.status).to eq 422
+      expect(product_without_image.images.count).to eq 0
+      expect(json_response["id"]).to eq nil
+      expect(json_response["errors"]).to include "Attachment has an invalid content type"
+    end
   end
 end