chore: Refactor type hinting in BaseBackend and its subclasses

src/blinkstick/backends/base.py

@@ -2,8 +2,12 @@
 
 from abc import ABC, abstractmethod
 
+from typing import TypeVar, Generic
 
-class BaseBackend(ABC):
+T = TypeVar("T")
+
+
+class BaseBackend(ABC, Generic[T]):
 
     serial: str | None
 
@@ -16,12 +20,12 @@ def _refresh_device(self):
 
     @staticmethod
     @abstractmethod
-    def find_blinksticks(find_all: bool = True):
+    def find_blinksticks(find_all: bool = True) -> list[T] | None:
         raise NotImplementedError
 
     @staticmethod
     @abstractmethod
-    def find_by_serial(serial: str) -> BaseBackend | None:
+    def find_by_serial(serial: str) -> list[T] | None:
         raise NotImplementedError
 
     @abstractmethod

src/blinkstick/backends/unix_like.py

@@ -1,16 +1,17 @@
 from __future__ import annotations
 
-import usb.core
-import usb.util
+import usb.core  # type: ignore
+import usb.util  # type: ignore
 
 from blinkstick.constants import VENDOR_ID, PRODUCT_ID
 from blinkstick.backends.base import BaseBackend
 from blinkstick.exceptions import BlinkStickException
 
 
-class UnixLikeBackend(BaseBackend):
+class UnixLikeBackend(BaseBackend[usb.core.Device]):
 
     serial: str
+    device: usb.core.Device
 
     def __init__(self, device=None):
         self.device = device
@@ -38,13 +39,13 @@ def _refresh_device(self):
             return True
 
     @staticmethod
-    def find_blinksticks(find_all: bool = True):
+    def find_blinksticks(find_all: bool = True) -> list[usb.core.Device] | None:
         return usb.core.find(
             find_all=find_all, idVendor=VENDOR_ID, idProduct=PRODUCT_ID
         )
 
     @staticmethod
-    def find_by_serial(serial: str) -> list | None:
+    def find_by_serial(serial: str) -> list[usb.core.Device] | None:
         for d in UnixLikeBackend.find_blinksticks():
             try:
                 if usb.util.get_string(d, 3, 1033) == serial:
@@ -53,6 +54,8 @@ def find_by_serial(serial: str) -> list | None:
             except Exception as e:
                 print("{0}".format(e))
 
+        return None
+
     def control_transfer(
         self,
         bmRequestType: int,

src/blinkstick/backends/win32.py

@@ -3,14 +3,18 @@
 import sys
 from ctypes import *
 
-from pywinusb import hid
+from pywinusb import hid  # type: ignore
 
 from blinkstick.constants import VENDOR_ID, PRODUCT_ID
 from blinkstick.backends.base import BaseBackend
 from blinkstick.exceptions import BlinkStickException
 
 
-class Win32Backend(BaseBackend):
+class Win32Backend(BaseBackend[hid.HidDevice]):
+    serial: str
+    device: hid.HidDevice
+    reports: list[hid.core.HidReport]
+
     def __init__(self, device=None):
         super().__init__()
         self.device = device
@@ -20,14 +24,16 @@ def __init__(self, device=None):
             self.serial = self.get_serial()
 
     @staticmethod
-    def find_by_serial(serial: str) -> list | None:
+    def find_by_serial(serial: str) -> list[hid.HidDevice] | None:
         devices = [
             d for d in Win32Backend.find_blinksticks() if d.serial_number == serial
         ]
 
         if len(devices) > 0:
             return devices
 
+        return None
+
     def _refresh_device(self):
         # TODO This is weird semantics. fix up return values to be more sensible
         if not self.serial:
@@ -39,7 +45,7 @@ def _refresh_device(self):
             return True
 
     @staticmethod
-    def find_blinksticks(find_all: bool = True):
+    def find_blinksticks(find_all: bool = True) -> list[hid.HidDevice] | None:
         devices = hid.HidDeviceFilter(
             vendor_id=VENDOR_ID, product_id=PRODUCT_ID
         ).get_devices()

src/blinkstick/blinkstick.py

@@ -1412,8 +1412,10 @@ def find_all() -> list[BlinkStick]:
     @rtype: BlinkStick[]
     @return: a list of BlinkStick objects or None if no devices found
     """
-    result = []
-    for d in USBBackend.find_blinksticks():
+    result: list[BlinkStick] = []
+    if (found_devices := USBBackend.find_blinksticks()) is None:
+        return result
+    for d in found_devices:
         result.extend([BlinkStick(device=d)])
 
     return result