use enum value in request validation (kubeflow#2249)

Other method such as `.predict` assume that the enum value is used for the protocol, but the validation checks against the actual enum instead.

Signed-off-by: luranhe <luranjhe@gmail.com>

python/kserve/kserve/model.py

@@ -107,13 +107,13 @@ def _grpc_client(self):
         return self._grpc_client_stub
 
     def validate(self, request):
-        if self.protocol == PredictorProtocol.REST_V2:
+        if self.protocol == PredictorProtocol.REST_V2.value:
             if "inputs" in request and not isinstance(request["inputs"], list):
                 raise tornado.web.HTTPError(
                     status_code=HTTPStatus.BAD_REQUEST,
                     reason="Expected \"inputs\" to be a list"
                 )
-        elif isinstance(request, Dict) or self.protocol == PredictorProtocol.REST_V1:
+        elif isinstance(request, Dict) or self.protocol == PredictorProtocol.REST_V1.value:
             if "instances" in request and not isinstance(request["instances"], list):
                 raise tornado.web.HTTPError(
                     status_code=HTTPStatus.BAD_REQUEST,

python/kserve/test/test_server.py

@@ -24,7 +24,9 @@
 from kserve import Model
 from kserve import ModelServer
 from kserve import ModelRepository
+from kserve.model import PredictorProtocol
 from tornado.httpclient import HTTPClientError
+from tornado.web import HTTPError
 from ray import serve
 
 
@@ -159,6 +161,26 @@ async def load(self, name: str) -> bool:
             return False
 
 
+class TestModel:
+
+    async def test_validate(self):
+        model = DummyModel("TestModel")
+        good_request = {"instances": []}
+        validated_request = model.validate(good_request)
+        assert validated_request == good_request
+        bad_request = {"instances": "invalid"}
+        with pytest.raises(HTTPError):
+            model.validate(bad_request)
+
+        model.protocol = PredictorProtocol.REST_V2.value
+        good_request = {"inputs": []}
+        validated_request = model.validate(good_request)
+        assert validated_request == good_request
+        bad_request = {"inputs": "invalid"}
+        with pytest.raises(HTTPError):
+            model.validate(bad_request)
+
+
 class TestTFHttpServer:
 
     @pytest.fixture(scope="class")