KIT-4352 Add validation exception handling

Author: oschulzSam

.idea/sag_py_web_common.iml

@@ -1,2 +1,4 @@
 asgi-logger>=0.1.0
-fastapi>=0.115.12, <1
+fastapi>=0.115.12, <1
+starlette>=0.46.2
+

requirements.txt

@@ -2,12 +2,14 @@
 from logging import Logger
 from typing import Any
 
-from fastapi.encoders import jsonable_encoder
 from fastapi.exception_handlers import http_exception_handler
+from fastapi.exceptions import RequestValidationError
 from fastapi.responses import JSONResponse
 from starlette.exceptions import HTTPException as StarletteHTTPException
 from starlette.responses import Response
 
+from sag_py_web_common.response_content import SimpleDetail, ValidationErrorDetail, ValidationErrorResponse
+
 logger: Logger = logging.getLogger("http_error_logger")
 
 
@@ -18,10 +20,26 @@ async def handle_unknown_exception(_: Any, exception: Exception) -> JSONResponse
         JSONResponse: A json response that contains the field 'detail' with the exception message.
     """
     logger.error("An unknown Error!", exc_info=True, extra={"response_status": 500})
-    return JSONResponse(status_code=500, content=jsonable_encoder({"detail": str(exception)}))
+    return JSONResponse(status_code=500, content=SimpleDetail(detail=str(exception)).model_dump())
 
 
 async def log_exception(_, exception: StarletteHTTPException) -> Response:  # type: ignore
     logger.error("An HTTP Error! %s", exception.detail, extra={"response_status": exception.status_code})
 
     return await http_exception_handler(_, exception)
+
+
+async def handle_validation_exception(_: Any, exception: RequestValidationError) -> JSONResponse:
+    errors = [
+        ValidationErrorDetail(**{
+            "loc": [str(loc) for loc in err["loc"]],
+            "msg": err["msg"],
+            "type": err["type"]
+        })
+        for err in exception.errors()
+    ]
+    logger.error("Validation Error!", exc_info=True, extra={"response_status": 422})
+    return JSONResponse(
+        status_code=422,
+        content=ValidationErrorResponse(detail=errors).model_dump()
+    )

sag_py_web_common/json_exception_handler.py

@@ -0,0 +1,16 @@
+from pydantic import BaseModel
+from typing import List
+
+
+class SimpleDetail(BaseModel):
+    detail: str
+
+
+class ValidationErrorDetail(BaseModel):
+    loc: List[str]
+    msg: str
+    type: str
+
+
+class ValidationErrorResponse(BaseModel):
+    detail: List[ValidationErrorDetail]

sag_py_web_common/response_content.py

@@ -1,11 +1,14 @@
 import logging
+from unittest.mock import Mock
 
 import pytest
 from _pytest.logging import LogCaptureFixture
+from fastapi.exceptions import RequestValidationError
 from fastapi.responses import JSONResponse
 from starlette.exceptions import HTTPException as StarletteHTTPException
 
 from sag_py_web_common import handle_unknown_exception, log_exception
+from sag_py_web_common.json_exception_handler import handle_validation_exception
 
 
 @pytest.mark.asyncio
@@ -18,6 +21,22 @@ async def test_handle_unknown_exception() -> None:
     assert result.body == b'{"detail":"error message"}'
 
 
+@pytest.mark.asyncio
+async def test_validation_exception_handler() -> None:
+    # Arrange
+    exc = RequestValidationError([{"loc": ("body", "title"), "msg": "field required", "type": "value_error.missing"}])
+    request = Mock()
+
+    # Act
+    result: JSONResponse = await handle_validation_exception(request, exc)
+
+    # Assert
+    assert result.status_code == 422
+    assert b'"msg":"field required"' in result.body
+    assert b'"type":"value_error.missing"' in result.body
+    assert b'"loc":["body","title"]' in result.body
+
+
 @pytest.mark.asyncio
 async def test_log_exception(caplog: LogCaptureFixture) -> None:
     # Arrange