Fix type checking - per device type annotations

src/escpos/printer/cups.py

@@ -11,7 +11,7 @@
 import functools
 import logging
 import tempfile
-from typing import Optional, Type
+from typing import Literal, Optional, Type, Union
 
 from ..escpos import Escpos
 from ..exceptions import DeviceNotFoundError
@@ -74,6 +74,8 @@ class CupsPrinter(Escpos):
 
     """
 
+    _device: Union[Literal[False], Literal[None], cups.Connection] = False
+
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.

src/escpos/printer/file.py

@@ -9,6 +9,7 @@
 """
 
 import logging
+from typing import IO, Literal, Optional, Union
 
 from ..escpos import Escpos
 from ..exceptions import DeviceNotFoundError
@@ -33,6 +34,8 @@ class File(Escpos):
 
     """
 
+    _device: Union[Literal[False], Literal[None], IO[bytes]] = False
+
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -67,7 +70,7 @@ class File(Escpos):
 
         try:
             # Open device
-            self.device = open(self.devfile, "wb")
+            self.device: Optional[IO[bytes]] = open(self.devfile, "wb")
         except OSError as e:
             # Raise exception or log error and cancel
             self.device = None
@@ -82,7 +85,8 @@ class File(Escpos):
 
     def flush(self) -> None:
         """Flush printing content."""
-        self.device.flush()
+        if self.device:
+            self.device.flush()
 
     def _raw(self, msg):
         """Print any command sent in raw format.
@@ -101,5 +105,5 @@ class File(Escpos):
         logging.info("Closing File connection to printer %s", self.devfile)
         if not self.auto_flush:
             self.flush()
-        self.device.close()
+        self._device.close()
         self._device = False

src/escpos/printer/lp.py

@@ -12,6 +12,7 @@ import functools
 import logging
 import subprocess
 import sys
+from typing import Literal, Optional, Union
 
 from ..escpos import Escpos
 from ..exceptions import DeviceNotFoundError
@@ -53,6 +54,8 @@ class LP(Escpos):
 
     """
 
+    _device: Union[Literal[False], Literal[None], subprocess.Popen] = False
+
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -132,7 +135,7 @@ class LP(Escpos):
             self.printer_name = self.printer_name or self._get_system_default_printer()
             assert self.printer_name in self.printers, "Incorrect printer name"
             # Open device
-            self.device = subprocess.Popen(
+            self.device: Optional[subprocess.Popen] = subprocess.Popen(
                 ["lp", "-d", self.printer_name, "-t", self.job_name, "-o", "raw"],
                 stdin=subprocess.PIPE,
                 stdout=subprocess.DEVNULL,
@@ -159,11 +162,14 @@ class LP(Escpos):
         self._is_closing = True
         if not self.auto_flush:
             self.flush()
-        self.device.terminate()
+        self._device.terminate()
         self._device = False
 
     def flush(self) -> None:
         """End line and wait for new commands."""
+        if not self.device or not self.device.stdin:
+            return
+
         if self._flushed:
             return
 

src/escpos/printer/network.py

@@ -10,7 +10,7 @@
 
 import logging
 import socket
-from typing import Union
+from typing import Literal, Optional, Union
 
 from ..escpos import Escpos
 from ..exceptions import DeviceNotFoundError
@@ -48,6 +48,8 @@ class Network(Escpos):
 
     """
 
+    _device: Union[Literal[False], Literal[None], socket.socket] = False
+
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -91,7 +93,9 @@ class Network(Escpos):
 
         try:
             # Open device
-            self.device = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+            self.device: Optional[socket.socket] = socket.socket(
+                socket.AF_INET, socket.SOCK_STREAM
+            )
             self.device.settimeout(self.timeout)
             self.device.connect((self.host, self.port))
         except OSError as e:
@@ -124,8 +128,8 @@ class Network(Escpos):
             return
         logging.info("Closing Network connection to printer %s", self.host)
         try:
-            self.device.shutdown(socket.SHUT_RDWR)
+            self._device.shutdown(socket.SHUT_RDWR)
         except socket.error:
             pass
-        self.device.close()
+        self._device.close()
         self._device = False

src/escpos/printer/serial.py

@@ -11,7 +11,7 @@
 
 import functools
 import logging
-from typing import Optional, Union
+from typing import Literal, Optional, Union
 
 from ..escpos import Escpos
 from ..exceptions import DeviceNotFoundError
@@ -64,6 +64,8 @@ class Serial(Escpos):
 
     """
 
+    _device: Union[Literal[False], Literal[None], serial.Serial] = False
+
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -170,7 +172,7 @@ class Serial(Escpos):
         if not self._device:
             return
         logging.info("Closing Serial connection to printer %s", self.devfile)
-        if self.device.is_open:
-            self.device.flush()
-            self.device.close()
+        if self._device and self._device.is_open:
+            self._device.flush()
+            self._device.close()
         self._device = False

src/escpos/printer/usb.py

@@ -9,7 +9,7 @@
 """
 import functools
 import logging
-from typing import Dict, Optional, Type, Union
+from typing import Dict, Literal, Optional, Type, Union
 
 from ..escpos import Escpos
 from ..exceptions import DeviceNotFoundError, USBNotFoundError
@@ -63,6 +63,8 @@ class Usb(Escpos):
 
     """
 
+    _device: Union[Literal[False], Literal[None], Type[usb.core.Device]] = False
+
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -197,5 +199,5 @@ class Usb(Escpos):
         logging.info(
             "Closing Usb connection to printer %s", tuple(self.usb_args.values())
         )
-        usb.util.dispose_resources(self.device)
+        usb.util.dispose_resources(self._device)
         self._device = False

src/escpos/printer/win32raw.py

@@ -10,6 +10,7 @@
 
 import functools
 import logging
+from typing import Literal, Optional, Union
 
 from ..escpos import Escpos
 from ..exceptions import DeviceNotFoundError
@@ -18,6 +19,7 @@ from ..exceptions import DeviceNotFoundError
 _DEP_WIN32PRINT = False
 
 try:
+    import _win32typing
     import pywintypes
     import win32print
 
@@ -63,6 +65,8 @@ class Win32Raw(Escpos):
 
     """
 
+    _device: Union[Literal[False], Literal[None], _win32typing.PyPrinterHANDLE] = False
+
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -111,7 +115,9 @@ class Win32Raw(Escpos):
             self.printer_name = self.printer_name or win32print.GetDefaultPrinter()
             assert self.printer_name in self.printers, "Incorrect printer name"
             # Open device
-            self.device = win32print.OpenPrinter(self.printer_name)
+            self.device: Optional[
+                _win32typing.PyPrinterHANDLE
+            ] = win32print.OpenPrinter(self.printer_name)
             if self.device:
                 self.current_job = win32print.StartDocPrinter(
                     hprinter=self.device, level=1, _tuple=(job_name, None, "RAW")
@@ -136,9 +142,9 @@ class Win32Raw(Escpos):
         if not self._device:
             return
         logging.info("Closing Win32Raw connection to printer %s", self.printer_name)
-        win32print.EndPagePrinter(self.device)
-        win32print.EndDocPrinter(self.device)
-        win32print.ClosePrinter(self.device)
+        win32print.EndPagePrinter(self._device)
+        win32print.EndDocPrinter(self._device)
+        win32print.ClosePrinter(self._device)
         self._device = False
 
     @dependency_win32print