feat: Register child devices as top level devices

src/blueapi/core/context.py

@@ -341,6 +341,10 @@ def register_device(self, device: Device, name: str | None = None) -> None:
         `name` parameter here. If the device conforms to a different protocol then
         the parameter must be used to name it.
 
+        Children of ophyd-async devices, including signals, are also registered
+        under their own names, e.g. registering "stage" also registers "stage-x"
+        and "stage-x-velocity".
+
         Args:
             device (Device): The device to register
             name (Optional[str], optional): A name for the device. Defaults to None.
@@ -358,7 +362,40 @@ def register_device(self, device: Device, name: str | None = None) -> None:
             else:
                 raise KeyError(f"Must supply a name for this device: {device}")
 
+        existing = self.devices.get(name)
+        if existing is not None and existing is not device:
+            LOGGER.warning("Replacing existing device registered as '%s'", name)
         self.devices[name] = device
+        self._register_children(device)
+
+    def _register_children(
+        self, device: Device, ancestor_names: frozenset[str] = frozenset()
+    ) -> None:
+        """Register the children of an ophyd-async device under their own names."""
+
+        if not isinstance(device, AsyncDevice):
+            return
+
+        ancestor_names = ancestor_names | {device.name}
+        for attr_name, child in device.children():
+            if child.name:
+                # Some children share an ancestor's name, e.g. a motor's
+                # user_readback, so name these after their attribute instead
+                if child.name in ancestor_names:
+                    name = f"{device.name}-{attr_name}"
+                else:
+                    name = child.name
+                existing = self.devices.setdefault(name, child)
+                if existing is not child:
+                    # Its children's names start with the clashing name, so skip
+                    # them too
+                    LOGGER.warning(
+                        "Not registering %s or its children, name '%s' is in use",
+                        child,
+                        name,
+                    )
+                    continue
+            self._register_children(child, ancestor_names)
 
     def unregister_all_devices(self):
         """Unregister all devices from the context."""

src/blueapi/service/interface.py

@@ -191,15 +191,21 @@ def get_plan(name: str) -> PlanModel:
 
 def get_devices() -> list[DeviceModel]:
     """Get all available devices in the BlueskyContext"""
-    return [DeviceModel.from_device(device) for device in context().devices.values()]
+    # Use the registered name, as some children are registered under a name
+    # other than their own, e.g. a motor's user_readback
+    return [
+        DeviceModel.from_device(device, name)
+        for name, device in context().devices.items()
+    ]
 
 
 def get_device(name: str) -> DeviceModel:
     """Retrieve device by name from the BlueskyContext"""
-    if not (device := context().find_device(name)):
+    ctx = context()
+    if not (device := ctx.find_device(name)):
         raise KeyError(name)
 
-    return DeviceModel.from_device(device)
+    return DeviceModel.from_device(device, name if name in ctx.devices else None)
 
 
 def submit_task(

src/blueapi/service/model.py

@@ -36,8 +36,9 @@ class DeviceModel(BlueapiBaseModel):
     )
 
     @classmethod
-    def from_device(cls, device: Device) -> "DeviceModel":
-        name = device.name if isinstance(device, HasName) else _UNKNOWN_NAME
+    def from_device(cls, device: Device, name: str | None = None) -> "DeviceModel":
+        if name is None:
+            name = device.name if isinstance(device, HasName) else _UNKNOWN_NAME
         return cls(name=name, protocols=list(_protocol_info(device)))