Add schema validation in CustomJSONField serializer

Add schema validation in CustomJSONField serializer

Author: AlexPetul

django_custom_jsonfield/rest_framework/serializers.py

@@ -1,16 +1,25 @@
 import jsonschema
 from django.utils.translation import gettext_lazy as _
+from jsonschema import validators
 from rest_framework import serializers
 
 
 class CustomJSONField(serializers.JSONField):
     default_error_messages = {
         "invalid_data": _("Value does not match the JSON schema."),
+        "invalid_schema": _("Invalid JSON schema."),
     }
 
     def __init__(self, schema: dict, **kwargs):
         self.schema = schema
         super().__init__(**kwargs)
+
+        validator = validators.validator_for(self.schema)
+        try:
+            validator.check_schema(self.schema)
+        except jsonschema.exceptions.SchemaError:
+            self.fail("invalid_schema")
+
         self.validators.append(self._validate_data)
 
     def _validate_data(self, value):

tests/test_openapi_schema.py

@@ -1,4 +1,5 @@
-from unittest.mock import Mock
+from typing import Any
+from unittest.mock import Mock, patch
 
 import pytest
 
@@ -53,12 +54,16 @@ def test_map_serializer_field_ok(schema: dict):
 @pytest.mark.parametrize(
     "schema",
     [
-        {
-            "type": "test",
-        },
+        {"type": "unknown_type"},
     ],
 )
-def test_map_serializer_field_invalid_schema(schema: dict):
+@patch(
+    "django_custom_jsonfield.rest_framework.serializers.jsonschema.validators.validator_for",
+    new=Mock(),
+)
+def test_map_serializer_field_fallback(schema: Any):
+    """Test fallback to string."""
+
     json_field = CustomJSONField(schema=schema)
     extension = CustomJSONFieldSerializerExtension(json_field)
     data = extension.map_serializer_field(Mock(), "response")

tests/test_serializer_field.py

@@ -1,6 +1,5 @@
 import pytest
-from rest_framework import serializers
-from rest_framework.exceptions import ErrorDetail
+from rest_framework import exceptions, serializers
 
 from django_custom_jsonfield.rest_framework.serializers import CustomJSONField
 
@@ -27,10 +26,29 @@ class FakeSerializer(serializers.Serializer):
 
     expected_errors = {
         "json_field": [
-            ErrorDetail(
+            exceptions.ErrorDetail(
                 string="Value does not match the JSON schema.",
                 code="invalid_data",
             ),
         ],
     }
     assert serializer.errors == expected_errors
+
+
+@pytest.mark.parametrize(
+    "schema",
+    [
+        {"minItems": "1"},
+        {"properties": 1},
+        {"pattern": "*invalid.regex"},
+    ],
+)
+def test_map_serializer_field_invalid_schema(schema: dict):
+    """Test serializer raises an exception if JSON schema is invalid."""
+
+    with pytest.raises(exceptions.ValidationError) as e:
+        CustomJSONField(schema=schema)
+
+    assert isinstance(e.value, exceptions.ValidationError)
+    assert e.value.detail[0] == "Invalid JSON schema."
+    assert e.value.detail[0].code == "invalid_schema"