fix: narrow Wall velocity validation errors

flow360/component/simulation/models/surface_models.py

@@ -308,7 +308,9 @@ class WallRotation(Flow360BaseModel):
     # pylint: disable=no-member
     center: LengthType.Point = pd.Field(description="The center of rotation")
     axis: Axis = pd.Field(description="The axis of rotation.")
-    angular_velocity: AngularVelocityType = pd.Field("The value of the angular velocity.")
+    angular_velocity: AngularVelocityType = pd.Field(
+        description="The value of the angular velocity."
+    )
     type_name: Literal["WallRotation"] = pd.Field("WallRotation", frozen=True)
     private_attribute_circle_mode: Optional[dict] = pd.Field(None)
 
@@ -321,6 +323,7 @@ class WallRotation(Flow360BaseModel):
 WallVelocityModelTypes = Annotated[
     Union[SlaterPorousBleed, WallRotation], pd.Field(discriminator="type_name")
 ]
+WALL_VELOCITY_MODEL_ADAPTER = pd.TypeAdapter(WallVelocityModelTypes)
 
 
 class WallFunction(Flow360BaseModel):
@@ -476,6 +479,15 @@ def _normalize_wall_function(cls, value):
             return None
         return value
 
+    @pd.field_validator("velocity", mode="before")
+    @classmethod
+    def _normalize_velocity(cls, value):
+        # Sadly we cannot add a discriminator to `velocity` directly because the alternative
+        # branch is `VelocityVectorType`, which compiles to a tuple schema instead of a model variant.
+        if isinstance(value, dict) and value.get("type_name") is not None:
+            return WALL_VELOCITY_MODEL_ADAPTER.validate_python(value)
+        return value
+
     @pd.model_validator(mode="after")
     def check_wall_function_conflict(self):
         """Check no setting is conflicting with the usage of wall function"""

tests/simulation/params/test_rotation.py

@@ -1,4 +1,5 @@
 import pytest
+from pydantic import ValidationError
 
 from flow360 import u
 from flow360.component.simulation.models.surface_models import Wall, WallRotation
@@ -49,6 +50,34 @@ def test_wall_angular_velocity():
     )
 
 
+def test_wall_rotation_missing_angular_velocity_reports_required_field():
+    with pytest.raises(ValidationError) as exc_info:
+        Wall.model_validate(
+            {
+                "name": "Wheel Front",
+                "type": "Wall",
+                "entities": {"stored_entities": []},
+                "velocity": {
+                    "axis": [0, -1, 0],
+                    "center": {"value": [0, 0, 0], "units": "m"},
+                    "type_name": "WallRotation",
+                },
+            }
+        )
+
+    errors = exc_info.value.errors()
+    angular_velocity_errors = [error for error in errors if error["loc"][-1] == "angular_velocity"]
+    assert len(angular_velocity_errors) == 1
+    assert angular_velocity_errors[0]["msg"] == "Field required"
+    assert all(
+        not any(
+            isinstance(segment, str) and ("tuple[" in segment or "function-plain[" in segment)
+            for segment in error["loc"]
+        )
+        for error in errors
+    )
+
+
 def test_rotation_expression_with_t_seconds():
 
     with pytest.raises(