Update datakey on describe (#16)

* update datakey on describe

* update datakey only for complex and array datatypes

* fix update_dtype bug

src/secop_ophyd/SECoPSignal.py

@@ -292,6 +292,19 @@ async def put(self, value: Any | None, wait=True, timeout=None):
 
     async def get_datakey(self, source: str) -> DataKey:
         """Metadata like source, dtype, shape, precision, units"""
+
+        if self.SECoP_type_info._is_composite or isinstance(
+            self.SECoPdtype_obj, ArrayOf
+        ):
+            # getlast cached value
+            dataset = await self._secclient.get_parameter(
+                **self.get_param_path(), trycache=True
+            )
+
+            # this ensures the datakey is updated to the latest cached value
+            SECoPReading(entry=dataset, secop_dt=self.SECoP_type_info)
+            self.describe_dict.update(self.SECoP_type_info.describe_dict)
+
         return self.describe_dict
 
     async def get_reading(self) -> Reading:

src/secop_ophyd/util.py

@@ -625,7 +625,7 @@ def update_dtype(self, input_val):
         self.dtype_str = self.numpy_dtype.str
         self.describe_dict["dtype_str"] = self.dtype_str
 
-        self.dtype_descr = str(self.numpy_dtype.descr)
+        self.dtype_descr = self.numpy_dtype.descr
         self.describe_dict["dtype_descr"] = self.dtype_descr
 
         self.describe_dict["dtype"] = self.dtype