Fix #91 -- Make products/orders that are not cancelable (#204)

* Make products/orders that are not cancellable
Update Unit Tests

* Make use of select_related instead of prefetch_related
Simplify cancellable logic
Migrations

* Simplify cancellable logic
Maske use of select_related instead of prefetch_related

* Fix cancelable condition bug

src/pretix/base/migrations/0032_item_allow_cancel.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.9 on 2016-08-22 10:23
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0031_auto_20160816_0648'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='item',
+            name='allow_cancel',
+            field=models.BooleanField(default=True, help_text='Whether this product might or not be cancelled.', verbose_name='Allow a product to be cancelled'),
+        ),
+    ]

src/pretix/base/migrations/0033_auto_20160822_1044.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.9 on 2016-08-22 10:44
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0032_item_allow_cancel'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='item',
+            name='allow_cancel',
+            field=models.BooleanField(default=True, help_text='Whether this product might or not be cancelled.', verbose_name='Allow product to be cancelled'),
+        ),
+    ]

src/pretix/base/migrations/0035_merge.py

@@ -0,0 +1,16 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.9 on 2016-08-31 21:04
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0033_auto_20160822_1044'),
+        ('pretixbase', '0034_auto_20160830_1952'),
+    ]
+
+    operations = [
+    ]

src/pretix/base/models/items.py

@@ -186,6 +186,11 @@ class Item(LoggedModel):
         help_text=_('This product will be hidden from the event page until the user enters a voucher '
                     'code that is specifically tied to this product (and not via a quota).')
     )
+    allow_cancel = models.BooleanField(
+        verbose_name=_('Allow product to be cancelled'),
+        default=True,
+        help_text=_('Whether this product might or not be cancelled.')
+    )
 
     class Meta:
         verbose_name = _("Product")

src/pretix/base/models/orders.py

@@ -243,7 +243,9 @@ class Order(LoggedModel):
 
     @property
     def can_user_cancel(self) -> bool:
-        return self.event.settings.cancel_allow_user
+        positions = self.positions.all().select_related('item')
+        cancelable = all([op.item.allow_cancel for op in positions])
+        return self.event.settings.cancel_allow_user and cancelable
 
     @property
     def is_expired_by_time(self):

src/pretix/control/forms/item.py

@@ -119,6 +119,7 @@ class ItemCreateForm(I18nModelForm):
             'admission',
             'default_price',
             'tax_rate',
+            'allow_cancel'
         ]
 
 
@@ -144,6 +145,7 @@ class ItemUpdateForm(I18nModelForm):
             'available_until',
             'require_voucher',
             'hide_without_voucher',
+            'allow_cancel'
         ]
 
 

src/pretix/control/templates/pretixcontrol/item/index.html

@@ -25,6 +25,7 @@
             {% bootstrap_field form.available_until layout="horizontal" %}
             {% bootstrap_field form.require_voucher layout="horizontal" %}
             {% bootstrap_field form.hide_without_voucher layout="horizontal" %}
+            {% bootstrap_field form.allow_cancel layout="horizontal" %}
         </fieldset>
         <div class="form-group submit-group">
             <button type="submit" class="btn btn-primary btn-save">

src/tests/base/test_models.py

@@ -393,6 +393,53 @@ class OrderTestCase(BaseQuotaTestCase):
         self.event.settings.set('last_order_modification_date', now() - timedelta(days=1))
         assert not self.order.can_modify_answers
 
+    def test_can_cancel_order(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=None, price=23)
+        assert self.order.can_user_cancel
+
+    def test_can_cancel_order_multiple(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        item2 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=None, price=23)
+        OrderPosition.objects.create(order=self.order, item=item2,
+                                     variation=None, price=23)
+        assert self.order.can_user_cancel
+
+    def test_can_not_cancel_order(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=False)
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=None, price=23)
+        assert self.order.can_user_cancel is False
+
+    def test_can_not_cancel_order_multiple(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=False)
+        item2 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=None, price=23)
+        OrderPosition.objects.create(order=self.order, item=item2,
+                                     variation=None, price=23)
+        assert self.order.can_user_cancel is False
+
+    def test_can_not_cancel_order_multiple_mixed(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=False)
+        item2 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=None, price=23)
+        OrderPosition.objects.create(order=self.order, item=item2,
+                                     variation=None, price=23)
+        assert self.order.can_user_cancel is False
+
 
 class ItemCategoryTest(TestCase):
     """