fix: Use vat rate based on the current cart's shipping address country

Author: sveneberth

src/viur/shop/modules/cart.py

@@ -696,6 +696,30 @@ def add_new_parent(self, leaf_skel, **kwargs):
         EVENT_SERVICE.call(Event.ARTICLE_CHANGED, skel=leaf_skel, deleted=False)
         return new_parent_skel
 
+    def get_cached_cart_skel(self, key: db.Key) -> SkeletonInstance_T[CartNodeSkel]:
+        cache = current.request_data.get().setdefault("shop_cache_cart_skel", {})
+        key = db.keyHelper(key, CartNodeSkel.kindName)
+        try:
+            parent_skel = cache[key]
+        except KeyError:
+            parent_skel = self.viewSkel("node")
+            assert parent_skel.read(key)
+            cache[key] = parent_skel
+        return parent_skel
+
+    def get_closest_node(
+        self,
+        start: SkeletonInstance_T[CartNodeSkel | CartItemSkel],
+        condition: (lambda skel: True),
+    ) -> SkeletonInstance_T[CartNodeSkel] | None:
+        while True:
+            parent_skel = self.get_cached_cart_skel(start["parententry"])
+            if condition(parent_skel):
+                return parent_skel  # type:ignore
+            if parent_skel["is_root_node"]:
+                return None  # NotFound
+            start = parent_skel
+
 
 try:
     Session.on_delete

src/viur/shop/types/price.py

@@ -268,11 +268,17 @@ def vat_rate_percentage(self) -> float:
 
         :return: VAT rate as float between 0.0 and 1.0.
         """
+        try:
+            country = self._shipping_address["dest"]["country"]
+        except (KeyError, TypeError):
+            country = None
+        # logger.debug(f"Using country: {country}")
         try:
             # FIXME: self.article_skel has here sometimes renderPreparation set,
             #        but toolkit.without_render_preparation is already called in __init__
             #        What's going on here?
             vat_rate = SHOP_INSTANCE.get().vat_rate.get_vat_rate_for_country(
+                country=country,
                 category=toolkit.without_render_preparation(self.article_skel)["shop_vat_rate_category"],
             )
         except ConfigurationError as e:  # TODO(discussion): Or re-raise or implement fallback?
@@ -292,6 +298,21 @@ def vat_included(self) -> float:
         except TypeError:  # One value is None
             return 0.0
 
+    @functools.cached_property
+    def _shipping_address(self):
+        """
+        Returns the shipping address for the closest cart node.
+        """
+        if not self.is_in_cart:
+            return None
+        res = SHOP_INSTANCE.get().cart.get_closest_node(
+            self.cart_leaf,
+            condition=lambda skel: skel["shipping_address"] is not None,
+        )
+        if res:
+            return res["shipping_address"]
+        return res
+
     def to_dict(self) -> dict:
         """
         Serializes the relevant pricing fields to a dictionary, suitable for frontend or API use.
@@ -302,7 +323,7 @@ def to_dict(self) -> dict:
         return {
             attr_name: getattr(self, attr_name)
             for attr_name, attr_value in vars(self.__class__).items()
-            if isinstance(attr_value, (property, functools.cached_property))
+            if isinstance(attr_value, (property, functools.cached_property)) and not attr_name.startswith("_")
         } | utils.json.loads(json.dumps({  # must be JSON serializable for vi renderer
             "cart_discounts": self.cart_discounts,
             "article_discount": self.article_discount,