Merge pull request #4116 from open-formulieren/issue/4096

[#4096] Fix validation of hidden radio component

src/openforms/formio/serializers.py

@@ -87,6 +87,9 @@ def _remove_validations_from_field(self, field: serializers.Field) -> None:
                 field.min_length = None
                 field.max_length = None
 
+            case serializers.ChoiceField():
+                field.allow_blank = True
+
     def _get_required(self) -> bool:
         return any(field.required for field in self.fields.values())
 

src/openforms/formio/tests/validation/test_radio.py

@@ -0,0 +1,31 @@
+from django.test import SimpleTestCase, tag
+
+from openforms.typing import JSONObject
+
+from ...typing import RadioComponent
+from .helpers import validate_formio_data
+
+
+class RadioValidationTests(SimpleTestCase):
+
+    @tag("gh-4096")
+    def test_radio_hidden_required(self):
+        component: RadioComponent = {
+            "type": "radio",
+            "key": "radio",
+            "label": "Radio",
+            "values": [
+                {"label": "Opt1", "value": "opt1"},
+                {"label": "Opt2", "value": "opt2"},
+            ],
+            "hidden": True,
+            "validate": {
+                "required": True,
+            },
+        }
+
+        # This happens when `clearOnHide` is `False`:
+        data: JSONObject = {"radio": ""}
+
+        is_valid, _ = validate_formio_data(component, data)
+        self.assertTrue(is_valid)