feat: Register child devices as top level devices

src/blueapi/core/context.py

@@ -132,6 +132,7 @@ class BlueskyContext:
     plan_functions: dict[str, PlanGenerator] = field(default_factory=dict)
 
     _reference_cache: dict[type, type] = field(default_factory=dict)
+    _warned_name_clash: bool = field(default=False, init=False, repr=False)
 
     def __post_init__(self, configuration: ApplicationConfig | None):
         if not configuration:
@@ -341,6 +342,11 @@ 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". If a name is already in use, the existing device
+        is kept and the new one and its children are not registered.
+
         Args:
             device (Device): The device to register
             name (Optional[str], optional): A name for the device. Defaults to None.
@@ -358,7 +364,39 @@ def register_device(self, device: Device, name: str | None = None) -> None:
             else:
                 raise KeyError(f"Must supply a name for this device: {device}")
 
-        self.devices[name] = device
+        if self._add_device(name, device):
+            self._register_children(device)
+
+    def _register_children(self, device: Device) -> None:
+        """Register the children of an ophyd-async device under their own names."""
+
+        if not isinstance(device, AsyncDevice):
+            return
+
+        for _, child in device.children():
+            if not child.name or self._add_device(child.name, child):
+                self._register_children(child)
+
+    def _add_device(self, name: str, device: Device) -> bool:
+        """Add a device unless a different one is already registered as name."""
+
+        existing = self.devices.setdefault(name, device)
+        if existing is not device:
+            # Expected for e.g. a motor's user_readback, which has the motor's name.
+            # The caller skips its children too, as their names start with this one
+            if not self._warned_name_clash:
+                LOGGER.warning(
+                    "Some devices were not registered as their names are in use, "
+                    "e.g. motor readbacks. Enable debug logging to see which"
+                )
+                self._warned_name_clash = True
+            LOGGER.debug(
+                "Not registering %s or its children, name '%s' is in use",
+                device,
+                name,
+            )
+            return False
+        return True
 
     def unregister_all_devices(self):
         """Unregister all devices from the context."""

src/blueapi/service/interface.py

@@ -191,15 +191,22 @@ 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()]
+    # Report each device under its registered name. A device registered under an
+    # override name would otherwise show its own name, which one of its children
+    # may be registered as, 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)))