Allow to print question answers on invoices

src/pretix/base/migrations/0133_auto_20190830_1513.py

@@ -0,0 +1,21 @@
+# Generated by Django 2.2.4 on 2019-08-30 15:13
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+import pretix.base.models.fields
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0132_auto_20190808_1253'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='question',
+            name='print_on_invoice',
+            field=models.BooleanField(default=False),
+        ),
+    ]

src/pretix/base/models/items.py

@@ -1034,6 +1034,10 @@ class Question(LoggedModel):
         help_text=_('This question will only show up in the backend.'),
         default=False
     )
+    print_on_invoice = models.BooleanField(
+        verbose_name=_('Print answer on invoices'),
+        default=False
+    )
     dependency_question = models.ForeignKey(
         'Question', null=True, blank=True, on_delete=models.SET_NULL, related_name='dependent_questions'
     )

src/pretix/base/services/invoices.py

@@ -129,7 +129,7 @@ def build_invoice(invoice: Invoice) -> Invoice:
         positions = list(
             invoice.order.positions.select_related('addon_to', 'item', 'tax_rule', 'subevent', 'variation').annotate(
                 addon_c=Count('addons')
-            ).order_by('positionid', 'id')
+            ).prefetch_related('answers', 'answers__question').order_by('positionid', 'id')
         )
 
         reverse_charge = False
@@ -146,6 +146,16 @@ def build_invoice(invoice: Invoice) -> Invoice:
                 desc = "  + " + desc
             if invoice.event.settings.invoice_attendee_name and p.attendee_name:
                 desc += "<br />" + pgettext("invoice", "Attendee: {name}").format(name=p.attendee_name)
+
+            for answ in p.answers.all():
+                if not answ.question.print_on_invoice:
+                    continue
+                desc += "<br />{}{} {}".format(
+                    answ.question.question,
+                    "" if str(answ.question.question).endswith("?") else ":",
+                    str(answ)
+                )
+
             if invoice.event.has_subevents:
                 desc += "<br />" + pgettext("subevent", "Date: {}").format(p.subevent)
             InvoiceLine.objects.create(