Allow to modify answers for pending orders

src/pretix/base/migrations/0018_auto_20150314_1232.py

@@ -0,0 +1,25 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+import versions.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0017_auto_20150308_1507'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='order',
+            name='status',
+            field=models.CharField(verbose_name='Status', choices=[('p', 'pending'), ('n', 'paid'), ('e', 'expired'), ('c', 'cancelled'), ('r', 'refunded')], max_length=3),
+        ),
+        migrations.AlterField(
+            model_name='orderposition',
+            name='order',
+            field=versions.models.VersionedForeignKey(verbose_name='Order', to='pretixbase.Order', related_name='positions'),
+        ),
+    ]

src/pretix/base/models.py

@@ -1,3 +1,4 @@
+from datetime import datetime
 from itertools import product
 import copy
 import uuid
@@ -1327,6 +1328,19 @@ class Order(Versionable):
                 self.code = code
                 return
 
+    @property
+    def can_modify_answers(self):
+        if self.status not in (Order.STATUS_PENDING, Order.STATUS_PAID, Order.STATUS_EXPIRED):
+            return False
+        modify_deadline = self.event.settings.get('last_order_modification_date', as_type=datetime)
+        if modify_deadline is not None and now() > modify_deadline:
+            return False
+        ask_names = self.event.settings.get('attendee_names_asked', as_type=bool)
+        for cp in self.positions.all().prefetch_related('item__questions'):
+            if (cp.item.admission and ask_names) or cp.item.questions.all():
+                return True
+        return False  # nothing there to modify
+
 
 class QuestionAnswer(Versionable):
     """
@@ -1376,7 +1390,8 @@ class OrderPosition(ObjectWithAnswers, Versionable):
     """
     order = VersionedForeignKey(
         Order,
-        verbose_name=_("Order")
+        verbose_name=_("Order"),
+        related_name='positions'
     )
     item = VersionedForeignKey(
         Item,

src/pretix/base/settings.py

@@ -1,6 +1,8 @@
+from datetime import datetime, date, time
 import json
 import decimal
 
+import dateutil.parser
 from django.db.models import Model
 from versions.models import Versionable
 
@@ -11,6 +13,7 @@ DEFAULTS = {
     'attendee_names_asked': 'True',
     'attendee_names_required': 'False',
     'reservation_time': '30',
+    'last_order_modification_date': None,
 }
 
 
@@ -51,6 +54,12 @@ class SettingsProxy:
             return json.loads(value)
         elif as_type == bool:
             return value == 'True'
+        elif as_type == datetime:
+            return dateutil.parser.parse(value)
+        elif as_type == date:
+            return dateutil.parser.parse(value).date()
+        elif as_type == time:
+            return dateutil.parser.parse(value).time()
         elif as_type == decimal.Decimal:
             return decimal.Decimal(value)
         elif issubclass(as_type, Versionable):
@@ -67,6 +76,8 @@ class SettingsProxy:
             return str(value)
         elif isinstance(value, list) or isinstance(value, dict):
             return json.dumps(value)
+        elif isinstance(value, datetime) or isinstance(value, date) or isinstance(value, time):
+            return value.isoformat()
         elif isinstance(value, Versionable):
             return value.identity
         elif isinstance(value, Model):