Fix #2016 -- Correct shredding of question answers with file attachments

src/pretix/base/shredder.py

@@ -1,4 +1,5 @@
 import json
+import os
 from datetime import timedelta
 from typing import List, Tuple
 
@@ -324,10 +325,16 @@ class QuestionAnswerShredder(BaseDataShredder):
     description = _('This will remove all answers to questions, as well as logged changes to them.')
 
     def generate_files(self) -> List[Tuple[str, str, str]]:
-        yield 'question-answers.json', 'application/json', json.dumps({
+        d = {}
-            '{}-{}'.format(op.order.code, op.positionid): AnswerSerializer(op.answers.all(), many=True).data
+        for op in OrderPosition.all.filter(order__event=self.event).prefetch_related('answers', 'answers__question'):
-            for op in OrderPosition.all.filter(order__event=self.event).prefetch_related('answers')
+            for a in op.answers.all():
-        }, indent=4)
+                if a.file:
+                    fname = f'{op.order.code}-{op.positionid}-{a.question.identifier}-{os.path.basename(a.file.name)}'
+                    yield fname, 'application/unknown', a.file.read()
+            d[f'{op.order.code}-{op.positionid}'] = AnswerSerializer(
+                sorted(op.answers.all(), key=lambda a: a.question_id), context={'request': None}, many=True
+            ).data
+        yield 'question-answers.json', 'application/json', json.dumps(d, indent=4)
 
     @transaction.atomic
     def shred_data(self):

src/tests/base/test_shredders.py

@@ -226,6 +226,7 @@ def test_invoice_address_shredder(event, order):
 @pytest.mark.django_db
 def test_question_answer_shredder(event, order, question):
     opt = question.options.first()
+    q2 = event.questions.create(question="Photo", type="F", identifier="DEF")
     l1 = order.log_action(
         'pretix.event.order.modified',
         data={
@@ -242,21 +243,33 @@ def test_question_answer_shredder(event, order, question):
         question=question,
         answer='S'
     )
+    qa2 = QuestionAnswer.objects.create(
+        orderposition=order.positions.first(),
+        question=q2,
+        answer='file:///foo.pdf'
+    )
     qa.file.save('foo.pdf', ContentFile('foo'))
     fname = qa.file.path
     assert os.path.exists(fname)
     qa.options.add(opt)
     s = QuestionAnswerShredder(event)
     f = list(s.generate_files())
-    assert json.loads(f[0][2]) == {
+    assert json.loads(f[-1][2]) == {
         '{}-1'.format(order.code): [{
             'question': question.pk,
             'answer': 'S',
             'question_identifier': question.identifier,
             'options': [opt.pk],
             'option_identifiers': [opt.identifier],
+        }, {
+            'question': q2.pk,
+            'answer': f'/api/v1/organizers/dummy/events/dummy/orderpositions/{qa2.orderposition_id}/answer/{qa2.question_id}/',
+            'question_identifier': q2.identifier,
+            'options': [],
+            'option_identifiers': [],
         }]
     }
+    assert f[0][0].endswith('.pdf')
     s.shred_data()
     order.refresh_from_db()
     assert not os.path.exists(fname)