support for str in mbbi/mbbo (#499)

closes #451

src/ophyd_async/epics/signal/_common.py

@@ -55,7 +55,7 @@ def get_supported_values(
  f"which do not match {datatype}, which has {choices}."
  )
  return {x: datatype(x) if x else "_" for x in pv_choices}
- elif datatype is None:
+ elif datatype is None or datatype is str:
  return {x: x or "_" for x in pv_choices}
 
  raise TypeError(

tests/epics/signal/test_common.py

@@ -35,8 +35,14 @@ class MyEnum(str, Enum):
  get_supported_values("", MyEnum, ("test",))
 
 
-def test_given_no_supplied_enum_then_returns_generated_choices_enum_with_pv_choices():
- supported_vals = get_supported_values("", None, ("test",))
+@pytest.mark.parametrize(
+ "datatype",
+ [None, str],
+)
+def test_given_no_enum_or_string_then_returns_generated_choices_enum_with_pv_choices(
+ datatype,
+):
+ supported_vals = get_supported_values("", datatype, ("test",))
  assert len(supported_vals) == 1
  assert "test" in supported_vals
 

tests/epics/signal/test_signals.py

@@ -769,6 +769,19 @@ async def test_str_enum_returns_enum(ioc: IOC):
  assert val == "Bbb"
 
 
+async def test_str_datatype_in_mbbo(ioc: IOC):
+ backend = await ioc.make_backend(MyEnum, "enum")
+ pv_name = f"{ioc.protocol}://{PV_PREFIX}:{ioc.protocol}:enum"
+ sig = epics_signal_rw(str, pv_name)
+ datakey = await backend.get_datakey(sig.source)
+ assert datakey["choices"] == ["Aaa", "Bbb", "Ccc"]
+ await sig.connect()
+ description = await sig.describe()
+ assert description[""]["choices"] == ["Aaa", "Bbb", "Ccc"]
+ val = await sig.get_value()
+ assert val == "Bbb"
+
+
 async def test_runtime_enum_returns_str(ioc: IOC):
  await ioc.make_backend(MySubsetEnum, "enum")
  pv_name = f"{ioc.protocol}://{PV_PREFIX}:{ioc.protocol}:enum"