Allow context to deal with new style unions and add tests (#436)

Fixes #432

src/blueapi/core/context.py

@@ -4,15 +4,8 @@
 from dataclasses import dataclass, field
 from importlib import import_module
 from inspect import Parameter, signature
-from types import ModuleType
-from typing import (
-    Any,
-    Generic,
-    TypeVar,
-    get_args,
-    get_origin,
-    get_type_hints,
-)
+from types import ModuleType, UnionType
+from typing import Any, Generic, TypeVar, Union, get_args, get_origin, get_type_hints
 
 from bluesky.run_engine import RunEngine, call_in_bluesky_event_loop
 from pydantic import create_model
@@ -264,7 +257,7 @@ def _type_spec_for_function(
             )
         return new_args
 
-    def _convert_type(self, typ: type) -> type:
+    def _convert_type(self, typ: type | Any) -> type:
         """
         Recursively convert a type to something that can be deserialised by
         pydantic. Bluesky protocols (and types that extend them) are replaced
@@ -288,6 +281,8 @@ def _convert_type(self, typ: type) -> type:
         if args:
             new_types = tuple(self._convert_type(i) for i in args)
             root = get_origin(typ)
+            if root == UnionType:
+                root = Union
             return root[new_types] if root else typ
         return typ
 

tests/core/test_context.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from typing import Union
 from unittest.mock import patch
 
 import pytest
@@ -274,6 +275,24 @@ def test_reference_type_conversion(empty_context: BlueskyContext) -> None:
     )
 
 
+def test_reference_type_conversion_union(empty_context: BlueskyContext) -> None:
+    movable_ref: type = empty_context._reference(Movable)
+    assert empty_context._convert_type(Movable) == movable_ref
+    assert (
+        empty_context._convert_type(Union[Movable, int]) == Union[movable_ref, int]  # noqa # type: ignore
+    )
+
+
+def test_reference_type_conversion_new_style_union(
+    empty_context: BlueskyContext,
+) -> None:
+    movable_ref: type = empty_context._reference(Movable)
+    assert empty_context._convert_type(Movable) == movable_ref
+    assert (
+        empty_context._convert_type(Movable | int) == movable_ref | int  # type: ignore
+    )
+
+
 def test_default_device_reference(empty_context: BlueskyContext) -> None:
     def default_movable(mov: Movable = "demo") -> MsgGenerator:  # type: ignore
         ...