Cross selling (#4185)

Product categories can now be marked as "cross-selling categories", causing them to 
appear in the add-on checkout step as additional recommendations, depending on 
their cross-selling visibility (always, only if certain products are already in the cart, or 
only if they qualify for a discount according to discount rules).

---------

Co-authored-by: Raphael Michel <michel@rami.io>
Co-authored-by: Richard Schreiber <schreiber@rami.io>

src/pretix/presale/views/__init__.py

@@ -318,14 +318,14 @@ def cart_exists(request):
 
 def get_cart(request):
     from pretix.presale.views.cart import get_or_create_cart_id
-    qqs = request.event.questions.all()
-    qqs = qqs.filter(ask_during_checkin=False, hidden=False)
 
     if not hasattr(request, '_cart_cache'):
         cart_id = get_or_create_cart_id(request, create=False)
         if not cart_id:
             request._cart_cache = CartPosition.objects.none()
         else:
+            qqs = request.event.questions.all()
+            qqs = qqs.filter(ask_during_checkin=False, hidden=False)
             request._cart_cache = CartPosition.objects.filter(
                 cart_id=cart_id, event=request.event
             ).annotate(

src/pretix/presale/views/cart.py

@@ -151,104 +151,114 @@ class CartActionMixin:
         except InvoiceAddress.DoesNotExist:
             return InvoiceAddress()
 
-    def _item_from_post_value(self, key, value, voucher=None, voucher_ignore_if_redeemed=False):
-        if value.strip() == '' or '_' not in key:
-            return
 
-        if not key.startswith('item_') and not key.startswith('variation_') and not key.startswith('seat_'):
-            return
-
-        parts = key.split("_")
-        price = self.request.POST.get('price_' + "_".join(parts[1:]), "")
-        subevent = None
-        if 'subevent' in self.request.POST:
-            try:
-                subevent = int(self.request.POST.get('subevent'))
-            except ValueError:
-                pass
-
-        if key.startswith('seat_'):
-            try:
-                return {
-                    'item': int(parts[1]),
-                    'variation': int(parts[2]) if len(parts) > 2 else None,
-                    'count': 1,
-                    'seat': value,
-                    'price': price,
-                    'voucher': voucher,
-                    'voucher_ignore_if_redeemed': voucher_ignore_if_redeemed,
-                    'subevent': subevent
-                }
-            except ValueError:
-                raise CartError(_('Please enter numbers only.'))
+def _item_from_post_value(request, key, value, voucher=None, voucher_ignore_if_redeemed=False):
+    if value.strip() == '' or '_' not in key:
+        return
 
+    subevent = None
+    if key.startswith('subevent_'):
         try:
-            amount = int(value)
+            parts = key.split('_', 2)
+            subevent = int(parts[1])
+            key = parts[2]
+        except ValueError:
+            pass
+    elif 'subevent' in request.POST:
+        try:
+            subevent = int(request.POST.get('subevent'))
         except ValueError:
-            raise CartError(_('Please enter numbers only.'))
-        if amount < 0:
-            raise CartError(_('Please enter positive numbers only.'))
-        elif amount == 0:
-            return
-
-        if key.startswith('item_'):
-            try:
-                return {
-                    'item': int(parts[1]),
-                    'variation': None,
-                    'count': amount,
-                    'price': price,
-                    'voucher': voucher,
-                    'voucher_ignore_if_redeemed': voucher_ignore_if_redeemed,
-                    'subevent': subevent
-                }
-            except ValueError:
-                raise CartError(_('Please enter numbers only.'))
-        elif key.startswith('variation_'):
-            try:
-                return {
-                    'item': int(parts[1]),
-                    'variation': int(parts[2]),
-                    'count': amount,
-                    'price': price,
-                    'voucher': voucher,
-                    'voucher_ignore_if_redeemed': voucher_ignore_if_redeemed,
-                    'subevent': subevent
-                }
-            except ValueError:
-                raise CartError(_('Please enter numbers only.'))
-
-    def _items_from_post_data(self):
-        """
-        Parses the POST data and returns a list of dictionaries
-        """
-
-        # Compatibility patch that makes the frontend code a lot easier
-        req_items = list(self.request.POST.lists())
-        if '_voucher_item' in self.request.POST and '_voucher_code' in self.request.POST:
-            req_items.append((
-                '%s' % self.request.POST['_voucher_item'], ('1',)
-            ))
             pass
 
-        items = []
-        if 'raw' in self.request.POST:
-            items += json.loads(self.request.POST.get("raw"))
-        for key, values in req_items:
-            for value in values:
-                try:
-                    item = self._item_from_post_value(key, value, self.request.POST.get('_voucher_code'),
-                                                      voucher_ignore_if_redeemed=self.request.POST.get('_voucher_ignore_if_redeemed') == 'on')
-                except CartError as e:
-                    messages.error(self.request, str(e))
-                    return
-                if item:
-                    items.append(item)
+    if not key.startswith('item_') and not key.startswith('variation_') and not key.startswith('seat_'):
+        return
 
-        if len(items) == 0:
-            messages.warning(self.request, _('You did not select any products.'))
-            return []
-        return items
+    parts = key.split("_")
+    price = request.POST.get('price_' + "_".join(parts[1:]), "")
+
+    if key.startswith('seat_'):
+        try:
+            return {
+                'item': int(parts[1]),
+                'variation': int(parts[2]) if len(parts) > 2 else None,
+                'count': 1,
+                'seat': value,
+                'price': price,
+                'voucher': voucher,
+                'voucher_ignore_if_redeemed': voucher_ignore_if_redeemed,
+                'subevent': subevent
+            }
+        except ValueError:
+            raise CartError(_('Please enter numbers only.'))
+
+    try:
+        amount = int(value)
+    except ValueError:
+        raise CartError(_('Please enter numbers only.'))
+    if amount < 0:
+        raise CartError(_('Please enter positive numbers only.'))
+    elif amount == 0:
+        return
+
+    if key.startswith('item_'):
+        try:
+            return {
+                'item': int(parts[1]),
+                'variation': None,
+                'count': amount,
+                'price': price,
+                'voucher': voucher,
+                'voucher_ignore_if_redeemed': voucher_ignore_if_redeemed,
+                'subevent': subevent
+            }
+        except ValueError:
+            raise CartError(_('Please enter numbers only.'))
+    elif key.startswith('variation_'):
+        try:
+            return {
+                'item': int(parts[1]),
+                'variation': int(parts[2]),
+                'count': amount,
+                'price': price,
+                'voucher': voucher,
+                'voucher_ignore_if_redeemed': voucher_ignore_if_redeemed,
+                'subevent': subevent
+            }
+        except ValueError:
+            raise CartError(_('Please enter numbers only.'))
+
+
+def _items_from_post_data(request, warn_if_empty=True):
+    """
+    Parses the POST data and returns a list of dictionaries
+    """
+
+    # Compatibility patch that makes the frontend code a lot easier
+    req_items = list(request.POST.lists())
+    if '_voucher_item' in request.POST and '_voucher_code' in request.POST:
+        req_items.append((
+            '%s' % request.POST['_voucher_item'], ('1',)
+        ))
+        pass
+
+    items = []
+    if 'raw' in request.POST:
+        items += json.loads(request.POST.get("raw"))
+    for key, values in req_items:
+        for value in values:
+            try:
+                item = _item_from_post_value(request, key, value, request.POST.get('_voucher_code'),
+                                             voucher_ignore_if_redeemed=request.POST.get('_voucher_ignore_if_redeemed') == 'on')
+            except CartError as e:
+                messages.error(request, str(e))
+                return
+            if item:
+                items.append(item)
+
+    if len(items) == 0 and warn_if_empty:
+        messages.warning(request, _('You did not select any products.'))
+        return []
+    return items
 
 
 @scopes_disabled()
@@ -534,7 +544,7 @@ class CartAdd(EventViewMixin, CartActionMixin, AsyncAction, View):
             cs = cart_session(request)
             widget_data = cs.get('widget_data', {})
 
-        items = self._items_from_post_data()
+        items = _items_from_post_data(self.request)
         if items:
             return self.do(self.request.event.id, items, cart_id, translation.get_language(),
                            self.invoice_address.pk, widget_data, self.request.sales_channel.identifier,

src/pretix/presale/views/event.py

@@ -111,7 +111,8 @@ def item_group_by_category(items):
     )
 
 
-def get_grouped_items(event, *, channel: SalesChannel, subevent=None, voucher=None, require_seat=0, base_qs=None, allow_addons=False,
+def get_grouped_items(event, *, channel: SalesChannel, subevent=None, voucher=None, require_seat=0, base_qs=None,
+                      allow_addons=False, allow_cross_sell=False,
                       quota_cache=None, filter_items=None, filter_categories=None, memberships=None,
                       ignore_hide_sold_out_for_item_ids=None):
     base_qs_set = base_qs is not None
@@ -193,7 +194,9 @@ def get_grouped_items(event, *, channel: SalesChannel, subevent=None, voucher=No
         )
     )
 
-    items = base_qs.using(settings.DATABASE_REPLICA).filter_available(channel=channel.identifier, voucher=voucher, allow_addons=allow_addons).select_related(
+    items = base_qs.using(settings.DATABASE_REPLICA).filter_available(
+        channel=channel.identifier, voucher=voucher, allow_addons=allow_addons, allow_cross_sell=allow_cross_sell
+    ).select_related(
         'category', 'tax_rule',  # for re-grouping
         'hidden_if_available',
     ).prefetch_related(