make it more restrictive

Author: bendhouseart

reproschema/models/model.py

@@ -246,6 +246,23 @@ class AdditionalProperty(Thing):
         description="Background image for drawing activities.",
     )
 
+    @model_validator(mode="after")
+    def validate_only_background_image_extra(self):
+        """Validate that only backgroundImage is allowed as an extra field."""
+        # Get any extra fields that weren't explicitly defined
+        extra_fields = getattr(self, "__pydantic_extra__", {})
+
+        if extra_fields:
+            # Since backgroundImage is now an explicit field, any extra fields are not allowed
+            extra_field_names = list(extra_fields.keys())
+            raise ValueError(
+                f"Extra fields are not permitted in AdditionalProperty. "
+                f"Only 'backgroundImage' is allowed as an additional field, "
+                f"but found: {extra_field_names}"
+            )
+
+        return self
+
     id: Optional[str] = Field(
         None,
         description="A unique identifier for an entity. Must be either a CURIE shorthand for a URI or a complete URI.",

reproschema/models/tests/test_schema.py

@@ -238,6 +238,33 @@ def test_background_image_always_allowed():
     )
 
 
+def test_extra_fields_rejected():
+    """Test that extra fields other than backgroundImage are rejected."""
+    activity_dict = {
+        "category": "Activity",
+        "id": "activity_with_invalid_extra.jsonld",
+        "prefLabel": {"en": "Activity with Invalid Extra Field"},
+        "description": {"en": "An activity with an invalid extra field"},
+        "schemaVersion": "1.0.0-rc4",
+        "version": "0.0.1",
+        "ui": {
+            "inputType": "radio",
+            "addProperties": [
+                {
+                    "isAbout": "item1",
+                    "variableName": "test_item",
+                    "backgroundImage": "./images/test.png",  # This is allowed
+                    "customTool": "special_pen",  # This should be rejected
+                }
+            ],
+        },
+    }
+
+    # This should fail because customTool is not allowed
+    with pytest.raises(ValueError, match="Extra fields are not permitted"):
+        Activity(**activity_dict)
+
+
 def test_activity_without_extra_fields_works():
     """Test that activities without extra fields work normally regardless of input type."""
     activity_dict = {