Experimental fix for numpy typing. Works only for returns

Author: julianstirling

src/labthings_fastapi/client/__init__.py

@@ -13,6 +13,7 @@
 import httpx
 from urllib.parse import urlparse, urljoin
 
+import numpy as np
 from pydantic import BaseModel
 
 from .outputs import ClientBlobOutput
@@ -159,7 +160,9 @@ def set_property(self, path: str, value: Any) -> None:
         r = self.client.put(urljoin(self.path, path), json=value)
         r.raise_for_status()
 
-    def invoke_action(self, path: str, **kwargs: Any) -> Any:
+    def invoke_action(
+        self, path: str, labthings_typehint: str | None, **kwargs: Any
+    ) -> Any:
         r"""Invoke an action on the Thing.
 
         This method will make the initial POST request to invoke an action,
@@ -205,7 +208,7 @@ def invoke_action(self, path: str, **kwargs: Any) -> Any:
                     href=invocation["output"]["href"],
                     client=self.client,
                 )
-            return invocation["output"]
+            return _adjust_type(invocation["output"], labthings_typehint)
         else:
             raise RuntimeError(f"Action did not complete successfully: {invocation}")
 
@@ -276,6 +279,15 @@ class Client(cls):  # type: ignore[valid-type, misc]
         return Client
 
 
+def _adjust_type(value: Any, labthings_typehint: str | None) -> Any:
+    """Adjust the return type based on labthings_typehint."""
+    if labthings_typehint is None:
+        return value
+    if labthings_typehint == "ndarray":
+        return np.array(value)
+    raise ValueError(f"No type of {labthings_typehint} known")
+
+
 class PropertyClientDescriptor:
     """A base class for properties on `.ThingClient` objects."""
 
@@ -361,9 +373,12 @@ def add_action(cls: type[ThingClient], action_name: str, action: dict) -> None:
     :param action: a dictionary representing the action, in :ref:`wot_td`
         format.
     """
+    labthings_typehint = action["output"].get("format", None)
 
     def action_method(self: ThingClient, **kwargs: Any) -> Any:
-        return self.invoke_action(action_name, **kwargs)
+        return self.invoke_action(
+            action_name, labthings_typehint=labthings_typehint, **kwargs
+        )
 
     if "output" in action and "type" in action["output"]:
         action_method.__annotations__["return"] = action["output"]["type"]

src/labthings_fastapi/thing_description/__init__.py

@@ -300,9 +300,12 @@ def type_to_dataschema(t: type, **kwargs: Any) -> DataSchema:
     :raise ValidationError: if the datatype cannot be represented
         by a `.DataSchema`.
     """
+    data_format = None
     if hasattr(t, "model_json_schema"):
         # The input should be a `BaseModel` subclass, in which case this works:
         json_schema = t.model_json_schema()
+        if "_labthings_typehint" in t.__private_attributes__:
+            data_format = t.__private_attributes__["_labthings_typehint"].default
     else:
         # In principle, the below should work for any type, though some
         # deferred annotations can go wrong.
@@ -319,6 +322,8 @@ def type_to_dataschema(t: type, **kwargs: Any) -> DataSchema:
         if k in schema_dict:
             del schema_dict[k]
     schema_dict.update(kwargs)
+    if data_format is not None:
+        schema_dict["format"] = data_format
     try:
         return DataSchema(**schema_dict)
     except ValidationError as ve:

src/labthings_fastapi/types/numpy.py

@@ -147,3 +147,15 @@ class DenumpifyingDict(RootModel):
 
     root: Annotated[Mapping, WrapSerializer(denumpify_serializer)]
     model_config = ConfigDict(arbitrary_types_allowed=True)
+
+
+class ArrayModel(RootModel):
+    """A model automatically used by actions as the return type for a numpy array.
+
+    This models is passed to FastAPI as the return model for any action that returns
+    a numpy array. The private typehint is saved as format information to allow
+    a ThingClient to reconstruct the array from the list sent over HTTP.
+    """
+
+    root: NDArray
+    _labthings_typehint: str = "ndarray"

src/labthings_fastapi/utilities/introspection.py

@@ -16,6 +16,9 @@
 from pydantic import BaseModel, ConfigDict, Field, RootModel
 from pydantic.main import create_model
 from fastapi.dependencies.utils import analyze_param, get_typed_signature
+import numpy as np
+
+from ..types.numpy import ArrayModel
 
 
 class EmptyObject(BaseModel):
@@ -178,6 +181,9 @@ def return_type(func: Callable) -> Type:
     else:
         # We use `get_type_hints` rather than just `sig.return_annotation`
         # because it resolves forward references, etc.
+        rtype = get_type_hints(func)["return"]
+        if isinstance(rtype, type) and issubclass(rtype, np.ndarray):
+            return ArrayModel
         type_hints = get_type_hints(func, include_extras=True)
         return type_hints["return"]
 

tests/test_numpy_type.py

@@ -1,18 +1,14 @@
 from __future__ import annotations
 
-from pydantic import BaseModel, RootModel
+from pydantic import BaseModel
 import numpy as np
 from fastapi.testclient import TestClient
 
 from labthings_fastapi.testing import create_thing_without_server
-from labthings_fastapi.types.numpy import NDArray, DenumpifyingDict
+from labthings_fastapi.types.numpy import NDArray, DenumpifyingDict, ArrayModel
 import labthings_fastapi as lt
 
 
-class ArrayModel(RootModel):
-    root: NDArray
-
-
 def check_field_works_with_list(data):
     class Model(BaseModel):
         a: NDArray