Speed up device creation and connection in mock mode (#641)

src/ophyd_async/core/__init__.py

@@ -83,6 +83,7 @@
     DEFAULT_TIMEOUT,
     CalculatableTimeout,
     Callback,
+    LazyMock,
     NotConnected,
     Reference,
     StrictEnum,
@@ -176,6 +177,7 @@
     "DEFAULT_TIMEOUT",
     "CalculatableTimeout",
     "Callback",
+    "LazyMock",
     "CALCULATE_TIMEOUT",
     "NotConnected",
     "Reference",

src/ophyd_async/core/_device.py

@@ -3,17 +3,15 @@
 import asyncio
 import sys
 from collections.abc import Coroutine, Iterator, Mapping, MutableMapping
+from functools import cached_property
 from logging import LoggerAdapter, getLogger
 from typing import Any, TypeVar
-from unittest.mock import Mock
 
 from bluesky.protocols import HasName
 from bluesky.run_engine import call_in_bluesky_event_loop, in_bluesky_event_loop
 
 from ._protocol import Connectable
-from ._utils import DEFAULT_TIMEOUT, NotConnected, wait_for_connection
-
-_device_mocks: dict[Device, Mock] = {}
+from ._utils import DEFAULT_TIMEOUT, LazyMock, NotConnected, wait_for_connection
 
 
 class DeviceConnector:
@@ -37,25 +35,23 @@ def create_children_from_annotations(self, device: Device):
         during ``__init__``.
         """
 
-    async def connect(
-        self,
-        device: Device,
-        mock: bool | Mock,
-        timeout: float,
-        force_reconnect: bool,
-    ):
+    async def connect_mock(self, device: Device, mock: LazyMock):
+        # Connect serially, no errors to gather up as in mock mode
+        for name, child_device in device.children():
+            await child_device.connect(mock=mock.child(name))
+
+    async def connect_real(self, device: Device, timeout: float, force_reconnect: bool):
         """Used during ``Device.connect``.
 
         This is called when a previous connect has not been done, or has been
         done in a different mock more. It should connect the Device and all its
         children.
         """
-        coros = {}
-        for name, child_device in device.children():
-            child_mock = getattr(mock, name) if mock else mock  # Mock() or False
-            coros[name] = child_device.connect(
-                mock=child_mock, timeout=timeout, force_reconnect=force_reconnect
-            )
+        # Connect in parallel, gathering up NotConnected errors
+        coros = {
+            name: child_device.connect(timeout=timeout, force_reconnect=force_reconnect)
+            for name, child_device in device.children()
+        }
         await wait_for_connection(**coros)
 
 
@@ -67,9 +63,8 @@ class Device(HasName, Connectable):
     parent: Device | None = None
     # None if connect hasn't started, a Task if it has
     _connect_task: asyncio.Task | None = None
-    # If not None, then this is the mock arg of the previous connect
-    # to let us know if we can reuse an existing connection
-    _connect_mock_arg: bool | None = None
+    # The mock if we have connected in mock mode
+    _mock: LazyMock | None = None
 
     def __init__(
         self, name: str = "", connector: DeviceConnector | None = None
@@ -83,10 +78,18 @@ def name(self) -> str:
         """Return the name of the Device"""
         return self._name
 
+    @cached_property
+    def _child_devices(self) -> dict[str, Device]:
+        return {}
+
     def children(self) -> Iterator[tuple[str, Device]]:
-        for attr_name, attr in self.__dict__.items():
-            if attr_name != "parent" and isinstance(attr, Device):
-                yield attr_name, attr
+        yield from self._child_devices.items()
+
+    @cached_property
+    def log(self) -> LoggerAdapter:
+        return LoggerAdapter(
+            getLogger("ophyd_async.devices"), {"ophyd_async_device_name": self.name}
+        )
 
     def set_name(self, name: str):
         """Set ``self.name=name`` and each ``self.child.name=name+"-child"``.
@@ -97,28 +100,33 @@ def set_name(self, name: str):
             New name to set
         """
         self._name = name
-        # Ensure self.log is recreated after a name change
-        self.log = LoggerAdapter(
-            getLogger("ophyd_async.devices"), {"ophyd_async_device_name": self.name}
-        )
+        # Ensure logger is recreated after a name change
+        if "log" in self.__dict__:
+            del self.log
         for child_name, child in self.children():
             child_name = f"{self.name}-{child_name.strip('_')}" if self.name else ""
             child.set_name(child_name)
 
     def __setattr__(self, name: str, value: Any) -> None:
+        # Bear in mind that this function is called *a lot*, so
+        # we need to make sure nothing expensive happens in it...
         if name == "parent":
             if self.parent not in (value, None):
                 raise TypeError(
                     f"Cannot set the parent of {self} to be {value}: "
                     f"it is already a child of {self.parent}"
                 )
-        elif isinstance(value, Device):
+        # ...hence not doing an isinstance check for attributes we
+        # know not to be Devices
+        elif name not in _not_device_attrs and isinstance(value, Device):
             value.parent = self
-        return super().__setattr__(name, value)
+            self._child_devices[name] = value
+        # ...and avoiding the super call as we know it resolves to `object`
+        return object.__setattr__(self, name, value)
 
     async def connect(
         self,
-        mock: bool | Mock = False,
+        mock: bool | LazyMock = False,
         timeout: float = DEFAULT_TIMEOUT,
         force_reconnect: bool = False,
     ) -> None:
@@ -133,26 +141,39 @@ async def connect(
         timeout:
             Time to wait before failing with a TimeoutError.
         """
-        uses_mock = bool(mock)
-        can_use_previous_connect = (
-            uses_mock is self._connect_mock_arg
-            and self._connect_task
-            and not (self._connect_task.done() and self._connect_task.exception())
-        )
-        if mock is True:
-            mock = Mock()  # create a new Mock if one not provided
-        if force_reconnect or not can_use_previous_connect:
-            self._connect_mock_arg = uses_mock
-            if self._connect_mock_arg:
-                _device_mocks[self] = mock
-            coro = self._connector.connect(
-                device=self, mock=mock, timeout=timeout, force_reconnect=force_reconnect
+        if mock:
+            # Always connect in mock mode serially
+            if isinstance(mock, LazyMock):
+                # Use the provided mock
+                self._mock = mock
+            elif not self._mock:
+                # Make one
+                self._mock = LazyMock()
+            await self._connector.connect_mock(self, self._mock)
+        else:
+            # Try to cache the connect in real mode
+            can_use_previous_connect = (
+                self._mock is None
+                and self._connect_task
+                and not (self._connect_task.done() and self._connect_task.exception())
             )
-            self._connect_task = asyncio.create_task(coro)
-
-        assert self._connect_task, "Connect task not created, this shouldn't happen"
-        # Wait for it to complete
-        await self._connect_task
+            if force_reconnect or not can_use_previous_connect:
+                self._mock = None
+                coro = self._connector.connect_real(self, timeout, force_reconnect)
+                self._connect_task = asyncio.create_task(coro)
+            assert self._connect_task, "Connect task not created, this shouldn't happen"
+            # Wait for it to complete
+            await self._connect_task
+
+
+_not_device_attrs = {
+    "_name",
+    "_children",
+    "_connector",
+    "_timeout",
+    "_mock",
+    "_connect_task",
+}
 
 
 DeviceT = TypeVar("DeviceT", bound=Device)

src/ophyd_async/core/_mock_signal_backend.py

@@ -1,13 +1,13 @@
 import asyncio
 from collections.abc import Callable
 from functools import cached_property
-from unittest.mock import AsyncMock, Mock
+from unittest.mock import AsyncMock
 
 from bluesky.protocols import Descriptor, Reading
 
 from ._signal_backend import SignalBackend, SignalDatatypeT
 from ._soft_signal_backend import SoftSignalBackend
-from ._utils import Callback
+from ._utils import Callback, LazyMock
 
 
 class MockSignalBackend(SignalBackend[SignalDatatypeT]):
@@ -16,7 +16,7 @@ class MockSignalBackend(SignalBackend[SignalDatatypeT]):
     def __init__(
         self,
         initial_backend: SignalBackend[SignalDatatypeT],
-        mock: Mock,
+        mock: LazyMock,
     ) -> None:
         if isinstance(initial_backend, MockSignalBackend):
             raise ValueError("Cannot make a MockSignalBackend for a MockSignalBackend")
@@ -34,19 +34,22 @@ def __init__(
 
         # use existing Mock if provided
         self.mock = mock
-        self.put_mock = AsyncMock(name="put", spec=Callable)
-        self.mock.attach_mock(self.put_mock, "put")
-
         super().__init__(datatype=self.initial_backend.datatype)
 
+    @cached_property
+    def put_mock(self) -> AsyncMock:
+        put_mock = AsyncMock(name="put", spec=Callable)
+        self.mock().attach_mock(put_mock, "put")
+        return put_mock
+
     def set_value(self, value: SignalDatatypeT):
         self.soft_backend.set_value(value)
 
     def source(self, name: str, read: bool) -> str:
         return f"mock+{self.initial_backend.source(name, read)}"
 
     async def connect(self, timeout: float) -> None:
-        pass
+        raise RuntimeError("It is not possible to connect a MockSignalBackend")
 
     @cached_property
     def put_proceeds(self) -> asyncio.Event:

src/ophyd_async/core/_mock_signal_utils.py

@@ -2,17 +2,26 @@
 from contextlib import asynccontextmanager, contextmanager
 from unittest.mock import AsyncMock, Mock
 
-from ._device import Device, _device_mocks
+from ._device import Device
 from ._mock_signal_backend import MockSignalBackend
-from ._signal import Signal, SignalR, _mock_signal_backends
+from ._signal import Signal, SignalConnector, SignalR
 from ._soft_signal_backend import SignalDatatypeT
+from ._utils import LazyMock
+
+
+def get_mock(device: Device | Signal) -> Mock:
+    mock = device._mock  # noqa: SLF001
+    assert isinstance(mock, LazyMock), f"Device {device} not connected in mock mode"
+    return mock()
 
 
 def _get_mock_signal_backend(signal: Signal) -> MockSignalBackend:
-    assert (
-        signal in _mock_signal_backends
+    connector = signal._connector  # noqa: SLF001
+    assert isinstance(connector, SignalConnector), f"Expected Signal, got {signal}"
+    assert isinstance(
+        connector.backend, MockSignalBackend
     ), f"Signal {signal} not connected in mock mode"
-    return _mock_signal_backends[signal]
+    return connector.backend
 
 
 def set_mock_value(signal: Signal[SignalDatatypeT], value: SignalDatatypeT):
@@ -45,12 +54,6 @@ def get_mock_put(signal: Signal) -> AsyncMock:
     return _get_mock_signal_backend(signal).put_mock
 
 
-def get_mock(device: Device | Signal) -> Mock:
-    if isinstance(device, Signal):
-        return _get_mock_signal_backend(device).mock
-    return _device_mocks[device]
-
-
 def reset_mock_put_calls(signal: Signal):
     backend = _get_mock_signal_backend(signal)
     backend.put_mock.reset_mock()

src/ophyd_async/core/_signal.py

@@ -4,7 +4,6 @@
 import functools
 from collections.abc import AsyncGenerator, Awaitable, Callable, Mapping
 from typing import Any, Generic, cast
-from unittest.mock import Mock
 
 from bluesky.protocols import (
     Locatable,
@@ -30,9 +29,14 @@
 )
 from ._soft_signal_backend import SoftSignalBackend
 from ._status import AsyncStatus
-from ._utils import CALCULATE_TIMEOUT, DEFAULT_TIMEOUT, CalculatableTimeout, Callback, T
-
-_mock_signal_backends: dict[Device, MockSignalBackend] = {}
+from ._utils import (
+    CALCULATE_TIMEOUT,
+    DEFAULT_TIMEOUT,
+    CalculatableTimeout,
+    Callback,
+    LazyMock,
+    T,
+)
 
 
 async def _wait_for(coro: Awaitable[T], timeout: float | None, source: str) -> T:
@@ -54,26 +58,28 @@ class SignalConnector(DeviceConnector):
     def __init__(self, backend: SignalBackend):
         self.backend = self._init_backend = backend
 
-    async def connect(
-        self,
-        device: Device,
-        mock: bool | Mock,
-        timeout: float,
-        force_reconnect: bool,
-    ):
-        if mock:
-            self.backend = MockSignalBackend(self._init_backend, mock)
-            _mock_signal_backends[device] = self.backend
-        else:
-            self.backend = self._init_backend
+    async def connect_mock(self, device: Device, mock: LazyMock):
+        self.backend = MockSignalBackend(self._init_backend, mock)
+
+    async def connect_real(self, device: Device, timeout: float, force_reconnect: bool):
+        self.backend = self._init_backend
         device.log.debug(f"Connecting to {self.backend.source(device.name, read=True)}")
         await self.backend.connect(timeout)
 
 
+class _ChildrenNotAllowed(dict[str, Device]):
+    def __setitem__(self, key: str, value: Device) -> None:
+        raise AttributeError(
+            f"Cannot add Device or Signal child {key}={value} of Signal, "
+            "make a subclass of Device instead"
+        )
+
+
 class Signal(Device, Generic[SignalDatatypeT]):
     """A Device with the concept of a value, with R, RW, W and X flavours"""
 
     _connector: SignalConnector
+    _child_devices = _ChildrenNotAllowed()  # type: ignore
 
     def __init__(
         self,
@@ -89,14 +95,6 @@ def source(self) -> str:
         """Like ca://PV_PREFIX:SIGNAL, or "" if not set"""
         return self._connector.backend.source(self.name, read=True)
 
-    def __setattr__(self, name: str, value: Any) -> None:
-        if name != "parent" and isinstance(value, Device):
-            raise AttributeError(
-                f"Cannot add Device or Signal {value} as a child of Signal {self}, "
-                "make a subclass of Device instead"
-            )
-        return super().__setattr__(name, value)
-
 
 class _SignalCache(Generic[SignalDatatypeT]):
     def __init__(self, backend: SignalBackend[SignalDatatypeT], signal: Signal):