Backport #4228 to V3.1

core/app/models/spree/promotion_code.rb

@@ -5,12 +5,12 @@ class Spree::PromotionCode < Spree::Base
   belongs_to :promotion_code_batch, class_name: "Spree::PromotionCodeBatch", optional: true
   has_many :adjustments
 
+  before_validation :normalize_code
+
   validates :value, presence: true, uniqueness: { allow_blank: true, case_sensitive: true }
   validates :promotion, presence: true
   validate :promotion_not_apply_automatically, on: :create
 
-  before_save :normalize_code
-
   self.whitelisted_ransackable_attributes = ['value']
 
   # Whether the promotion code has exceeded its usage restrictions

core/spec/models/spree/promotion_code_spec.rb

@@ -8,22 +8,54 @@
 
     describe '#normalize_code' do
       let(:promotion) { create(:promotion, code: code) }
-      let(:promotion_code) { promotion.codes.first }
 
       before { subject }
 
-      context 'with mixed case' do
-        let(:code) { 'NewCoDe' }
+      context 'when no other code with the same value exists' do
+        let(:promotion_code) { promotion.codes.first }
 
-        it 'downcases the value before saving' do
-          expect(promotion_code.value).to eq('newcode')
+        context 'with mixed case' do
+          let(:code) { 'NewCoDe' }
+
+          it 'downcases the value before saving' do
+            expect(promotion_code.value).to eq('newcode')
+          end
+        end
+
+        context 'with extra spacing' do
+          let(:code) { ' new code ' }
+
+          it 'removes surrounding whitespace' do
+            expect(promotion_code.value).to eq 'new code'
+          end
         end
       end
 
-      context 'with extra spacing' do
-        let(:code) { ' new code ' }
-        it 'removes surrounding whitespace' do
-          expect(promotion_code.value).to eq 'new code'
+      context 'when another code with the same value exists' do
+        let(:promotion_code) { promotion.codes.build(value: code) }
+
+        context 'with mixed case' do
+          let(:code) { 'NewCoDe' }
+
+          it 'does not save the record and marks it as invalid' do
+            expect(promotion_code.valid?).to eq false
+
+            expect(promotion_code.errors.messages[:value]).to contain_exactly(
+              'has already been taken'
+            )
+          end
+        end
+
+        context 'with extra spacing' do
+          let(:code) { ' new code ' }
+
+          it 'does not save the record and marks it as invalid' do
+            expect(promotion_code.valid?).to eq false
+
+            expect(promotion_code.errors.messages[:value]).to contain_exactly(
+              'has already been taken'
+            )
+          end
         end
       end
     end