Ensure ActionDescriptor.output_model is always a model.

I've used `wrap_plain_types_in_rootmodel` to encapsulate action return types in a RootModel
if they are not already BaseModel subclasses. This stops annotations from being lost when actions are returned.

I needed to slightly adjust a test that checked action output models, I think that change is uncontroversial.

Author: rwb27

src/labthings_fastapi/actions.py

@@ -41,7 +41,7 @@
 
 from .base_descriptor import BaseDescriptor
 from .logs import add_thing_log_destination
-from .utilities import model_to_dict
+from .utilities import model_to_dict, wrap_plain_types_in_rootmodel
 from .invocations import InvocationModel, InvocationStatus, LogRecordModel
 from .dependencies.invocation import NonWarningInvocationID
 from .exceptions import (
@@ -477,7 +477,6 @@ def list_all_invocations(
 
         @app.get(
             ACTION_INVOCATIONS_PATH + "/{id}",
-            response_model=InvocationModel,
             responses={404: {"description": "Invocation ID not found"}},
         )
         def action_invocation(
@@ -683,7 +682,7 @@ def __init__(
             remove_first_positional_arg=True,
             ignore=[p.name for p in self.dependency_params],
         )
-        self.output_model = return_type(func)
+        self.output_model = wrap_plain_types_in_rootmodel(return_type(func))
         self.invocation_model = create_model(
             f"{name}_invocation",
             __base__=InvocationModel,

tests/test_actions.py

@@ -161,7 +161,7 @@ def action_wrapper(*args, **kwargs):
     return action_wrapper
 
 
-def assert_input_models_equivalent(model_a, model_b):
+def assert_models_equivalent(model_a, model_b):
     """Check two basemodels are equivalent."""
     keys = list(model_a.model_fields.keys())
     assert list(model_b.model_fields.keys()) == keys
@@ -198,11 +198,10 @@ def decorated(
             """An example decorated action with type annotations."""
             return 0.5
 
-    assert_input_models_equivalent(
-        Example.action.input_model, Example.decorated.input_model
+    assert_models_equivalent(Example.action.input_model, Example.decorated.input_model)
+    assert_models_equivalent(
+        Example.action.output_model, Example.decorated.output_model
     )
-    assert Example.action.output_model == Example.decorated.output_model
-
     # Check we can make the thing and it has a valid TD
     example = create_thing_without_server(Example)
     example.validate_thing_description()