normalize promotion code before validation

core/app/models/spree/promotion.rb

@@ -28,6 +28,8 @@ class Promotion < Spree::Base
 
     before_save :normalize_blank_values
 
+    before_validation :normalize_code
+
     scope :coupons, -> { where.not(code: nil) }
     scope :advertised, -> { where(advertise: true) }
     scope :applied, lambda {
@@ -227,6 +229,10 @@ def normalize_blank_values
       end
     end
 
+    def normalize_code
+      self.code = code.strip if code.present?
+    end
+
     def match_all?
       match_policy == 'all'
     end

core/spec/models/spree/promotion_spec.rb

@@ -25,6 +25,38 @@
       expect(@valid_promotion).not_to be_valid
     end
 
+    describe 'code should be unique' do
+      let(:code) { 'code' }
+
+      context 'code is unique' do
+        before do
+          @valid_promotion.code = code
+        end
+
+        it { expect(@valid_promotion).to be_valid }
+      end
+
+      context 'code is not unique' do
+        let!(:promotion_with_code) { Spree::Promotion.create! name: 'test1', code: code }
+
+        context 'code is identical' do
+          before do
+            @valid_promotion.code = code
+          end
+
+          it { expect(@valid_promotion).not_to be_valid }
+        end
+
+        context 'code is identical with whitespace' do
+          before do
+            @valid_promotion.code = code + ' '
+          end
+
+          it { expect(@valid_promotion).not_to be_valid }
+        end
+      end
+    end
+
     describe 'expires_at_must_be_later_than_starts_at' do
       before do
         @valid_promotion.starts_at = Date.today