Add unlimited_items_per_order-flag to Sales Channels (#1508)

* Add unlimited_items_per_order-flag to Sales Channels

* Test for unlimited_items_per_order Sales Channels-flag

* Fix test

src/pretix/base/channels.py

@@ -53,6 +53,14 @@ class SalesChannel:
         """
         return True
 
+    @property
+    def unlimited_items_per_order(self) -> bool:
+        """
+        If this property is ``True``, purchases made using this sales channel are not limited to the maximum amount of
+        items defined in the event settings.
+        """
+        return False
+
 
 def get_all_sales_channels():
     global _ALL_CHANNELS

src/pretix/base/services/cart.py

@@ -12,6 +12,7 @@ from django.utils.timezone import make_aware, now
 from django.utils.translation import pgettext_lazy, ugettext as _
 from django_scopes import scopes_disabled
 
+from pretix.base.channels import get_all_sales_channels
 from pretix.base.i18n import language
 from pretix.base.models import (
     CartPosition, Event, InvoiceAddress, Item, ItemBundle, ItemVariation, Seat,
@@ -218,13 +219,14 @@ class CartManager:
         })
 
     def _check_max_cart_size(self):
-        cartsize = self.positions.filter(addon_to__isnull=True).count()
-        cartsize += sum([op.count for op in self._operations if isinstance(op, self.AddOperation) and not op.addon_to])
-        cartsize -= len([1 for op in self._operations if isinstance(op, self.RemoveOperation) if
-                         not op.position.addon_to_id])
-        if cartsize > int(self.event.settings.max_items_per_order):
-            # TODO: i18n plurals
-            raise CartError(_(error_messages['max_items']) % (self.event.settings.max_items_per_order,))
+        if not get_all_sales_channels()[self._sales_channel].unlimited_items_per_order:
+            cartsize = self.positions.filter(addon_to__isnull=True).count()
+            cartsize += sum([op.count for op in self._operations if isinstance(op, self.AddOperation) and not op.addon_to])
+            cartsize -= len([1 for op in self._operations if isinstance(op, self.RemoveOperation) if
+                             not op.position.addon_to_id])
+            if cartsize > int(self.event.settings.max_items_per_order):
+                # TODO: i18n plurals
+                raise CartError(_(error_messages['max_items']) % (self.event.settings.max_items_per_order,))
 
     def _check_item_constraints(self, op):
         if isinstance(op, self.AddOperation) or isinstance(op, self.ExtendOperation):

src/pretix/presale/views/event.py

@@ -17,6 +17,7 @@ from django.views import View
 from django.views.decorators.csrf import csrf_exempt
 from django.views.generic import TemplateView
 
+from pretix.base.channels import get_all_sales_channels
 from pretix.base.models import ItemVariation, Quota, SeatCategoryMapping
 from pretix.base.models.event import SubEvent
 from pretix.base.models.items import ItemBundle
@@ -119,7 +120,10 @@ def get_grouped_items(event, subevent=None, voucher=None, channel='web', require
             item.available_variations = [v for v in item.available_variations
                                          if v.pk == voucher.variation_id]
 
-        max_per_order = item.max_per_order or int(event.settings.max_items_per_order)
+        if get_all_sales_channels()[channel].unlimited_items_per_order:
+            max_per_order = sys.maxsize
+        else:
+            max_per_order = item.max_per_order or int(event.settings.max_items_per_order)
 
         if item.hidden_if_available:
             q = item.hidden_if_available.availability(_cache=quota_cache)