API: Enforce that Item.default_price can't be null

src/pretix/api/serializers/item.py

@@ -184,6 +184,8 @@ class ItemSerializer(I18nAwareModelSerializer):
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
+        self.fields['default_price'].allow_null = False
+        self.fields['default_price'].required = True
         if not self.read_only:
             self.fields['require_membership_types'].queryset = self.context['event'].organizer.membership_types.all()
             self.fields['grant_membership_type'].queryset = self.context['event'].organizer.membership_types.all()

src/tests/api/test_items.py

@@ -476,6 +476,39 @@ def test_item_create(token_client, organizer, event, item, category, taxrule, me
         assert Item.objects.get(pk=resp.data['id']).require_membership_types.count() == 1
 
 
+@pytest.mark.django_db
+def test_item_create_price_required(token_client, organizer, event, item, category, taxrule):
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/items/'.format(organizer.slug, event.slug),
+        {
+            "category": category.pk,
+            "name": {
+                "en": "Ticket"
+            },
+            "active": True,
+            "description": None,
+        },
+        format='json'
+    )
+    assert resp.status_code == 400
+    assert resp.data == {"default_price": ["This field is required."]}
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/items/'.format(organizer.slug, event.slug),
+        {
+            "category": category.pk,
+            "name": {
+                "en": "Ticket"
+            },
+            "active": True,
+            "description": None,
+            "default_price": None,
+        },
+        format='json'
+    )
+    assert resp.status_code == 400
+    assert resp.data == {"default_price": ["This field may not be null."]}
+
+
 @pytest.mark.django_db
 def test_item_create_with_variation(token_client, organizer, event, item, category, taxrule):
     resp = token_client.post(