Order creation API: Allow to create orders without payment provider

src/pretix/api/serializers/order.py

@@ -555,7 +555,7 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
         min_length=5
     )
     comment = serializers.CharField(required=False, allow_blank=True)
-    payment_provider = serializers.CharField(required=True)
+    payment_provider = serializers.CharField(required=False, allow_null=True)
     payment_info = CompatibleJSONField(required=False)
     consume_carts = serializers.ListField(child=serializers.CharField(), required=False)
     force = serializers.BooleanField(default=False, required=False)
@@ -573,6 +573,8 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                   'force', 'send_mail')
 
     def validate_payment_provider(self, pp):
+        if pp is None:
+            return None
         if pp not in self.context['event'].get_payment_providers():
             raise ValidationError('The given payment provider is not known.')
         return pp
@@ -642,7 +644,7 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
     def create(self, validated_data):
         fees_data = validated_data.pop('fees') if 'fees' in validated_data else []
         positions_data = validated_data.pop('positions') if 'positions' in validated_data else []
-        payment_provider = validated_data.pop('payment_provider')
+        payment_provider = validated_data.pop('payment_provider', None)
         payment_info = validated_data.pop('payment_info', '{}')
         payment_date = validated_data.pop('payment_date', now())
         force = validated_data.pop('force', False)
@@ -832,6 +834,8 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
         elif payment_provider == "free" and order.total != Decimal('0.00'):
             raise ValidationError('You cannot use the "free" payment provider for non-free orders.')
         elif validated_data.get('status') == Order.STATUS_PAID:
+            if not payment_provider:
+                raise ValidationError('You cannot create a paid order without a payment provider.')
             order.payments.create(
                 amount=order.total,
                 provider=payment_provider,

src/tests/api/test_orders.py

@@ -2495,21 +2495,6 @@ def test_order_create_free(token_client, organizer, event, item, quota, question
     assert p.state == "confirmed"
 
 
-@pytest.mark.django_db
-def test_order_create_require_payment_provider(token_client, organizer, event, item, quota, question):
-    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
-    del res['payment_provider']
-    res['positions'][0]['item'] = item.pk
-    res['positions'][0]['answers'][0]['question'] = question.pk
-    resp = token_client.post(
-        '/api/v1/organizers/{}/events/{}/orders/'.format(
-            organizer.slug, event.slug
-        ), format='json', data=res
-    )
-    assert resp.status_code == 400
-    assert resp.data == {'payment_provider': ['This field is required.']}
-
-
 @pytest.mark.django_db
 def test_order_create_invalid_payment_provider(token_client, organizer, event, item, quota, question):
     res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
@@ -2853,6 +2838,35 @@ def test_order_create_send_emails_paid(token_client, organizer, event, item, quo
     assert djmail.outbox[1].subject == "Payment received for your order: {}".format(resp.data['code'])
 
 
+@pytest.mark.django_db
+def test_order_paid_require_payment_method(token_client, organizer, event, item, quota, question):
+    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['answers'][0]['question'] = question.pk
+    del res['payment_provider']
+    res['status'] = 'p'
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 400
+    assert resp.data == [
+        'You cannot create a paid order without a payment provider.'
+    ]
+
+    res['status'] = "n"
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 201
+    with scopes_disabled():
+        o = Order.objects.get(code=resp.data['code'])
+        assert not o.payments.exists()
+
+
 @pytest.mark.django_db
 def test_order_create_auto_pricing(token_client, organizer, event, item, quota, question):
     res = copy.deepcopy(ORDER_CREATE_PAYLOAD)