clarify messaging, extract optional fields into constant

Author: saptarshi-baseten

truss/base/truss_config.py

@@ -616,6 +616,13 @@ class TrussConfig(custom_types.ConfigModel):
     apply_library_patches: bool = True
     spec_version: str = "2.0"
 
+    DOCKER_SERVER_OPTIONAL_FIELDS: ClassVar[list[str]] = [
+        "server_port",
+        "predict_endpoint",
+        "readiness_endpoint",
+        "liveness_endpoint",
+    ]
+
     class Config:
         protected_namespaces = ()  # Silence warnings about fields starting with `model_`.
 
@@ -728,33 +735,22 @@ def _validate_docker_server(self) -> "TrussConfig":
         if is_grpc:
             if not has_docker_server:
                 raise ValueError(
-                    "docker_server is required when transport kind is GRPC"
+                    "docker_server is required when transport kind is gRPC"
                 )
-            optional_fields = [
-                "server_port",
-                "predict_endpoint",
-                "readiness_endpoint",
-                "liveness_endpoint",
-            ]
             if any(
                 getattr(self.docker_server, field) is not None
-                for field in optional_fields
+                for field in TrussConfig.DOCKER_SERVER_OPTIONAL_FIELDS
             ):
                 raise ValueError(
-                    "When transport kind is GRPC, docker_server should only have start_command defined"
+                    "When transport kind is gRPC, docker_server should only have start_command defined"
                 )
         elif has_docker_server:
-            optional_fields = [
-                "server_port",
-                "predict_endpoint",
-                "readiness_endpoint",
-                "liveness_endpoint",
-            ]
             if any(
-                getattr(self.docker_server, field) is None for field in optional_fields
+                getattr(self.docker_server, field) is None
+                for field in TrussConfig.DOCKER_SERVER_OPTIONAL_FIELDS
             ):
                 raise ValueError(
-                    "When transport kind is not GRPC, docker_server must either be absent or have server_port, predict_endpoint, readiness_endpoint, and liveness_endpoint defined"
+                    "Please define server_port, predict_endpoint, readiness_endpoint, and liveness_endpoint for docker_server"
                 )
 
         return self

truss/tests/test_config.py

@@ -982,15 +982,13 @@ def test_supported_versions_are_sorted():
 @pytest.mark.parametrize(
     "transport_config",
     [
-        # Valid GRPC config
         pytest.param(
             {
                 "runtime": {"transport": {"kind": "grpc"}},
                 "docker_server": {"start_command": "python main.py"},
             },
             id="valid-grpc-minimal",
         ),
-        # Valid HTTP config
         pytest.param(
             {
                 "runtime": {"transport": {"kind": "http"}},
@@ -1004,7 +1002,6 @@ def test_supported_versions_are_sorted():
             },
             id="valid-http-full",
         ),
-        # Valid WebSocket config
         pytest.param(
             {
                 "runtime": {"transport": {"kind": "websocket"}},
@@ -1018,7 +1015,6 @@ def test_supported_versions_are_sorted():
             },
             id="valid-websocket-full",
         ),
-        # Valid HTTP with no docker_server
         pytest.param(
             {"runtime": {"transport": {"kind": "http"}}}, id="valid-http-no-docker"
         ),
@@ -1036,7 +1032,6 @@ def test_valid_transport_configurations(transport_config, tmp_path):
 @pytest.mark.parametrize(
     "invalid_config,expected_error",
     [
-        # GRPC with additional fields
         pytest.param(
             {
                 "runtime": {"transport": {"kind": "grpc"}},
@@ -1046,22 +1041,20 @@ def test_valid_transport_configurations(transport_config, tmp_path):
                     "predict_endpoint": "/predict",
                 },
             },
-            "When transport kind is GRPC, docker_server should only have start_command defined",
+            "When transport kind is gRPC, docker_server should only have start_command defined",
             id="invalid-grpc-extra-fields",
         ),
-        # HTTP with missing fields
         pytest.param(
             {
                 "runtime": {"transport": {"kind": "http"}},
                 "docker_server": {"start_command": "./start.sh", "server_port": 8080},
             },
-            "When transport kind is not GRPC, docker_server must either be absent or have server_port, predict_endpoint, readiness_endpoint, and liveness_endpoint defined",
+            "Please define server_port, predict_endpoint, readiness_endpoint, and liveness_endpoint for docker_server",
             id="invalid-http-missing-fields",
         ),
-        # Missing docker_server with GRPC
         pytest.param(
             {"runtime": {"transport": {"kind": "grpc"}}},
-            "docker_server is required when transport kind is GRPC",
+            "docker_server is required when transport kind is gRPC",
             id="invalid-grpc-missing-docker",
         ),
     ],