Refactor Methods to allow overridding @command methods

Tag existing method with __unbound_command__ / __unbound_scan__ instead
of replacing with callable Command / Scan
Check attributes for this metadata in _bind_attrs
Store Command / Scan instances in self.__command_methods / self.__scan
Replace search in build_controller_api with accessing these members
Remove lazy imports from controller and replace with TYPE_CHECKING
import in methods. This feels more natural, as controllers needs methods
for isinstance checks, whereas methods just needs controllers for type
hinting.

e.g.
/workspaces/fastcs-eiger/src/fastcs_eiger/controllers/odin/eiger_odin_controller.py:28:15
- error: "arm_when_ready" overrides symbol of same name in class
"EigerController"
    "UnboundCommand[EigerOdinController]" is not assignable to
"UnboundCommand[EigerController]"
        Type parameter "Controller_T@UnboundCommand" is invariant, but
"EigerOdinController" is not the same as "EigerController"
(reportIncompatibleVariableOverride)

Author: GDYendell

docs/conf.py

@@ -89,7 +89,7 @@
     ("py:class", "p4p.nt.ndarray.NTNDArray"),
     ("py:class", "p4p.nt.NTTable"),
     # Problems in FastCS itself
-    ("py:class", "T"),
+    ("py:class", "BaseController"),
     ("py:class", "AttrIOUpdateCallback"),
     ("py:class", "fastcs.transports.epics.pva.pvi_tree._PviSignalInfo"),
     ("py:class", "fastcs.logging._logging.LogLevel"),

src/fastcs/control_system.py

@@ -8,7 +8,7 @@
 
 from fastcs.controllers import BaseController, Controller
 from fastcs.logging import bind_logger
-from fastcs.methods import Command, Scan, ScanCallback
+from fastcs.methods import ScanCallback
 from fastcs.tracer import Tracer
 from fastcs.transports import ControllerAPI, Transport
 
@@ -174,23 +174,11 @@ def build_controller_api(controller: Controller) -> ControllerAPI:
 
 
 def _build_controller_api(controller: BaseController, path: list[str]) -> ControllerAPI:
-    scan_methods: dict[str, Scan] = {}
-    command_methods: dict[str, Command] = {}
-    for attr_name in dir(controller):
-        attr = getattr(controller, attr_name)
-        match attr:
-            case Scan(enabled=True):
-                scan_methods[attr_name] = attr
-            case Command(enabled=True):
-                command_methods[attr_name] = attr
-            case _:
-                pass
-
     return ControllerAPI(
         path=path,
         attributes=controller.attributes,
-        scan_methods=scan_methods,
-        command_methods=command_methods,
+        command_methods=controller.command_methods,
+        scan_methods=controller.scan_methods,
         sub_apis={
             name: _build_controller_api(sub_controller, path + [name])
             for name, sub_controller in controller.sub_controllers.items()

src/fastcs/controllers/base_controller.py

@@ -7,6 +7,7 @@
 
 from fastcs.attributes import AnyAttributeIO, Attribute, AttrR, AttrW, HintedAttribute
 from fastcs.logging import bind_logger
+from fastcs.methods import Command, Scan, UnboundCommand, UnboundScan
 from fastcs.tracer import Tracer
 
 logger = bind_logger(logger_name=__name__)
@@ -46,6 +47,8 @@ def __init__(
         # Internal state that should not be accessed directly by base classes
         self.__attributes: dict[str, Attribute] = {}
         self.__sub_controllers: dict[str, BaseController] = {}
+        self.__command_methods: dict[str, Command] = {}
+        self.__scan_methods: dict[str, Scan] = {}
 
         self.__hinted_attributes: dict[str, HintedAttribute] = {}
         self.__hinted_sub_controllers: dict[str, type[BaseController]] = {}
@@ -95,10 +98,6 @@ class method and a controller instance, so that it can be called from any
         context with the controller instance passed as the ``self`` argument.
 
         """
-        # Lazy import to avoid circular references
-        from fastcs.methods.command import UnboundCommand
-        from fastcs.methods.scan import UnboundScan
-
         # Using a dictionary instead of a set to maintain order.
         class_dir = {key: None for key in dir(type(self)) if not key.startswith("_")}
         class_type_hints = {
@@ -114,8 +113,21 @@ class method and a controller instance, so that it can be called from any
             attr = getattr(self, attr_name, None)
             if isinstance(attr, Attribute):
                 setattr(self, attr_name, deepcopy(attr))
-            elif isinstance(attr, UnboundScan | UnboundCommand):
-                setattr(self, attr_name, attr.bind(self))
+            else:
+                if isinstance(attr, Command):
+                    self.add_command(attr_name, attr)
+                elif isinstance(attr, Scan):
+                    self.add_scan(attr_name, attr)
+                elif isinstance(
+                    unbound_command := getattr(attr, "__unbound_command__", None),
+                    UnboundCommand,
+                ):
+                    self.add_command(attr_name, unbound_command.bind(self))
+                elif isinstance(
+                    unbound_scan := getattr(attr, "__unbound_scan__", None),
+                    UnboundScan,
+                ):
+                    self.add_scan(attr_name, unbound_scan.bind(self))
 
     def _validate_io(self, ios: Sequence[AnyAttributeIO]):
         """Validate that there is exactly one AttributeIO class registered to the
@@ -137,6 +149,10 @@ def __repr__(self):
     def __setattr__(self, name, value):
         if isinstance(value, Attribute):
             self.add_attribute(name, value)
+        elif isinstance(value, Command):
+            self.add_command(name, value)
+        elif isinstance(value, Scan):
+            self.add_scan(name, value)
         elif isinstance(value, BaseController):
             self.add_sub_controller(name, value)
         else:
@@ -300,3 +316,19 @@ def add_sub_controller(self, name: str, sub_controller: BaseController):
     @property
     def sub_controllers(self) -> dict[str, BaseController]:
         return self.__sub_controllers
+
+    def add_command(self, name: str, command: Command):
+        self.__command_methods[name] = command
+        super().__setattr__(name, command)
+
+    @property
+    def command_methods(self) -> dict[str, Command]:
+        return self.__command_methods
+
+    def add_scan(self, name: str, scan: Scan):
+        self.__scan_methods[name] = scan
+        super().__setattr__(name, scan)
+
+    @property
+    def scan_methods(self) -> dict[str, Scan]:
+        return self.__scan_methods

src/fastcs/methods/__init__.py

@@ -1,6 +1,8 @@
 from .command import Command as Command
 from .command import CommandCallback as CommandCallback
+from .command import UnboundCommand as UnboundCommand
 from .command import command as command
 from .scan import Scan as Scan
 from .scan import ScanCallback as ScanCallback
+from .scan import UnboundScan as UnboundScan
 from .scan import scan as scan

src/fastcs/methods/command.py

@@ -1,10 +1,13 @@
 from collections.abc import Callable, Coroutine
 from types import MethodType
+from typing import TYPE_CHECKING
 
-from fastcs.controllers import BaseController
 from fastcs.logging import bind_logger
 from fastcs.methods.method import Controller_T, Method
 
+if TYPE_CHECKING:
+    from fastcs.controllers import BaseController  # noqa: F401
+
 logger = bind_logger(logger_name=__name__)
 
 UnboundCommandCallback = Callable[[Controller_T], Coroutine[None, None, None]]
@@ -13,7 +16,7 @@
 """A Command callback that is bound and can be called without `self`"""
 
 
-class Command(Method[BaseController]):
+class Command(Method["BaseController"]):
     """A `Controller` `Method` that performs a single action when called.
 
     This class contains a function that is bound to a specific `Controller` instance and
@@ -34,7 +37,7 @@ async def __call__(self):
         return await self.fn()
 
     @property
-    def fn(self):
+    def fn(self) -> CommandCallback:
         async def command():
             try:
                 return await self._fn()
@@ -70,15 +73,12 @@ def _validate(self, fn: UnboundCommandCallback[Controller_T]) -> None:
     def bind(self, controller: Controller_T) -> Command:
         return Command(MethodType(self.fn, controller), group=self.group)
 
-    def __call__(self):
-        raise NotImplementedError(
-            "Method must be bound to a controller instance to be callable"
-        )
-
 
 def command(
     *, group: str | None = None
-) -> Callable[[UnboundCommandCallback[Controller_T]], UnboundCommand[Controller_T]]:
+) -> Callable[
+    [UnboundCommandCallback[Controller_T]], UnboundCommandCallback[Controller_T]
+]:
     """Decorator to register a `Controller` method as a `Command`
 
     The `Command` will be passed to the transport layer to expose in the API
@@ -89,7 +89,9 @@ def command(
 
     def wrapper(
         fn: UnboundCommandCallback[Controller_T],
-    ) -> UnboundCommand[Controller_T]:
-        return UnboundCommand(fn, group=group)
+    ) -> UnboundCommandCallback[Controller_T]:
+        setattr(fn, "__unbound_command__", UnboundCommand(fn, group=group))  # noqa: B010
+
+        return fn
 
     return wrapper

src/fastcs/methods/method.py

@@ -1,14 +1,16 @@
 from asyncio import iscoroutinefunction
 from collections.abc import Callable, Coroutine
 from inspect import Signature, getdoc, signature
-from typing import Generic, TypeVar
+from typing import TYPE_CHECKING, Generic, TypeVar
 
-from fastcs.controllers.base_controller import BaseController
 from fastcs.tracer import Tracer
 
+if TYPE_CHECKING:
+    from fastcs.controllers import BaseController  # noqa: F401
+
 MethodCallback = Callable[..., Coroutine[None, None, None]]
 """Generic protocol for all `Controller` Method callbacks"""
-Controller_T = TypeVar("Controller_T", bound=BaseController)
+Controller_T = TypeVar("Controller_T", bound="BaseController")  # noqa: F821
 """Generic `Controller` class that an unbound method must be called with as `self`"""
 
 

src/fastcs/methods/scan.py

@@ -1,10 +1,13 @@
 from collections.abc import Callable, Coroutine
 from types import MethodType
+from typing import TYPE_CHECKING
 
-from fastcs.controllers import BaseController
 from fastcs.logging import bind_logger
 from fastcs.methods.method import Controller_T, Method
 
+if TYPE_CHECKING:
+    from fastcs.controllers import BaseController  # noqa: F401
+
 logger = bind_logger(logger_name=__name__)
 
 UnboundScanCallback = Callable[[Controller_T], Coroutine[None, None, None]]
@@ -13,7 +16,7 @@
 """A Scan callback that is bound and can be called without `self`"""
 
 
-class Scan(Method[BaseController]):
+class Scan(Method["BaseController"]):
     """A `Controller` `Method` that will be called periodically in the background.
 
     This class contains a function that is bound to a specific `Controller` instance and
@@ -40,7 +43,7 @@ async def __call__(self):
         return await self._fn()
 
     @property
-    def fn(self):
+    def fn(self) -> ScanCallback:
         async def scan():
             try:
                 return await self._fn()
@@ -80,15 +83,10 @@ def _validate(self, fn: UnboundScanCallback[Controller_T]) -> None:
     def bind(self, controller: Controller_T) -> Scan:
         return Scan(MethodType(self.fn, controller), self._period)
 
-    def __call__(self):
-        raise NotImplementedError(
-            "Method must be bound to a controller instance to be callable"
-        )
-
 
 def scan(
     period: float,
-) -> Callable[[UnboundScanCallback[Controller_T]], UnboundScan[Controller_T]]:
+) -> Callable[[UnboundScanCallback[Controller_T]], UnboundScanCallback[Controller_T]]:
     """Decorator to register a `Controller` method as a `Scan`
 
     The `Scan` method will be called periodically in the background.
@@ -97,7 +95,11 @@ def scan(
     if period <= 0:
         raise ValueError("Scan method must have a positive scan period")
 
-    def wrapper(fn: UnboundScanCallback[Controller_T]) -> UnboundScan[Controller_T]:
-        return UnboundScan(fn, period)
+    def wrapper(
+        fn: UnboundScanCallback[Controller_T],
+    ) -> UnboundScanCallback[Controller_T]:
+        setattr(fn, "__unbound_scan__", UnboundScan(fn, period=period))  # noqa: B010
+
+        return fn
 
     return wrapper

src/fastcs/transports/controller_api.py

@@ -88,7 +88,7 @@ def _add_attribute_update_tasks(
 
 
 def _get_periodic_scan_coros(
-    scan_dict: dict[float, list[Scan]],
+    scan_dict: dict[float, list[ScanCallback]],
 ) -> list[ScanCallback]:
     periodic_scan_coros: list[ScanCallback] = []
     for period, methods in scan_dict.items():
@@ -97,11 +97,13 @@ def _get_periodic_scan_coros(
     return periodic_scan_coros
 
 
-def _create_periodic_scan_coro(period: float, scans: list[Scan]) -> ScanCallback:
+def _create_periodic_scan_coro(
+    period: float, scans: list[ScanCallback]
+) -> ScanCallback:
     async def _sleep():
         await asyncio.sleep(period)
 
-    methods = [_sleep] + scans  # Create periodic behavior
+    methods = [_sleep] + list(scans)  # Create periodic behavior
 
     async def scan_coro() -> None:
         while True:

tests/test_control_system.py

@@ -22,7 +22,7 @@ async def test_scan_tasks(controller):
 
     for _ in range(3):
         count = controller.count
-        await asyncio.sleep(controller.counter.period + 0.01)
+        await asyncio.sleep(0.1)
         assert controller.count > count
 
 

tests/test_methods.py

@@ -39,17 +39,13 @@ async def do_nothing(self):
         async def do_nothing_with_arg(self, arg):
             pass
 
-    unbound_command = UnboundCommand(TestController.do_nothing, group="Test")
-
-    with pytest.raises(NotImplementedError):
-        await unbound_command()
-
     with pytest.raises(TypeError):
         UnboundCommand(TestController.do_nothing_with_arg)  # type: ignore
 
     with pytest.raises(TypeError):
         Command(TestController().do_nothing_with_arg)  # type: ignore
 
+    unbound_command = UnboundCommand(TestController.do_nothing, group="Test")
     command = unbound_command.bind(TestController())
     # Test that group is passed when binding commands
     assert command.group == "Test"
@@ -66,19 +62,14 @@ async def update_nothing(self):
         async def update_nothing_with_arg(self, arg):
             pass
 
-    unbound_scan = UnboundScan(TestController.update_nothing, 1.0)
-
-    assert unbound_scan.period == 1.0
-
-    with pytest.raises(NotImplementedError):
-        await unbound_scan()
-
     with pytest.raises(TypeError):
         UnboundScan(TestController.update_nothing_with_arg, 1.0)  # type: ignore
 
     with pytest.raises(TypeError):
         Scan(TestController().update_nothing_with_arg, 1.0)  # type: ignore
 
+    unbound_scan = UnboundScan(TestController.update_nothing, 1.0)
+    assert unbound_scan.period == 1.0
     scan = unbound_scan.bind(TestController())
 
     assert scan.period == 1.0