Set automatically correct promotion_type during coupon creation

backend/api/products_serializers.py

@@ -18,9 +18,6 @@
     Tag,
 )
 
-COUPON_PROMOTION_TYPE_API_ERROR_MESSAGE = (
-    f"Указан неверный тип промоакции, нужно выбрать {Promotion.COUPON}."
-)
 RATING_DECIMAL_PLACES = 1
 
 
@@ -516,6 +513,8 @@ def setup_eager_loading(cls, queryset, user):
 class CouponSerializer(serializers.ModelSerializer):
     """Serializer for coupons representation."""
 
+    promotion_type = serializers.ReadOnlyField()
+
     class Meta:
         model = Coupon
         fields = (
@@ -533,12 +532,6 @@ class Meta:
             "image",
         )
 
-    def validate_promotion_type(self, value):
-        """Checks that promotion_type is correct."""
-        if value != Promotion.COUPON:
-            raise serializers.ValidationError(COUPON_PROMOTION_TYPE_API_ERROR_MESSAGE)
-        return value
-
 
 class CouponApplySerializer(serializers.ModelSerializer):
     """Serializer to apply coupon promoaction to the order."""

backend/api/products_views.py

@@ -577,6 +577,12 @@ class CouponViewSet(DestroyWithPayloadMixin, viewsets.ModelViewSet):
     serializer_class = CouponSerializer
     permission_classes = [IsAdminOrReadOnly]
 
+    @transaction.atomic
+    def perform_create(self, serializer):
+        """Sets the correct promotion_type during coupon creation."""
+        serializer.save(promotion_type=Promotion.COUPON)
+        return super().perform_create(serializer)
+
 
 @method_decorator(
     name="list",
@@ -664,13 +670,19 @@ def get_queryset(self):
 
     @transaction.atomic
     def perform_create(self, serializer):
+        """
+        Sets the correct category for the given subcategory during product creation.
+        """
         subcategory_id = serializer._kwargs["data"]["subcategory"]
         subcategory = Subcategory.objects.get(id=subcategory_id)
         serializer.save(category=subcategory.parent_category)
         return super().perform_create(serializer)
 
     @transaction.atomic
     def perform_update(self, serializer):
+        """
+        Sets the correct category for the given subcategory during product editing.
+        """
         subcategory_id = serializer._kwargs["data"].get("subcategory")
         if subcategory_id:
             subcategory = Subcategory.objects.get(id=subcategory_id)

backend/api/reviews_views.py

@@ -101,10 +101,12 @@ def get_queryset(self):
         ).select_related("product", "author")
 
     def perform_create(self, serializer):
+        """Sets the correct author and product during review creation."""
         product = get_object_or_404(Product, pk=self.kwargs.get("product_id"))
         serializer.save(author=self.request.user, product=product)
 
     def perform_update(self, serializer):
+        """Updates pub_date and was_edited fields during review editing."""
         serializer.save(pub_date=timezone.now(), was_edited=True)
         return super().perform_update(serializer)