[libgpiod][PATCH 07/22] bindings: python: fix Chip union-attr type errors

[Vincent Fazio <vfazio@xxxxxxxxxxx>]

Since `Chip._chip` can be `None`, it's necessary to inform type checkers
of the state of the object to silence the union-attr errors.

Type checkers may not be able to infer that an object is not `None` from
an earlier call (such as `_check_closed`).

Instead of littering the code with "# type: ignore" comments, use casts
to inform type checkers that objects are not `None`.

Using `assert` is another option, however this duplicates the logic in
`_check_closed` so is redundant at best and, at worst, is not a safe
replacement as `assert` can be elided in optimized Python environments
and these checks need to be runtime enforced.

Signed-off-by: Vincent Fazio <vfazio@xxxxxxxxxxx>
---
 bindings/python/gpiod/chip.py | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/bindings/python/gpiod/chip.py b/bindings/python/gpiod/chip.py
index 4aa5677f94caf8c5d863aa6d75915a5b650de137..fe7bcfe082d6e9f6220093d3fc45ff232b5d0d17 100644
--- a/bindings/python/gpiod/chip.py
+++ b/bindings/python/gpiod/chip.py
@@ -7,7 +7,7 @@ from collections import Counter
 from datetime import timedelta
 from errno import ENOENT
 from types import TracebackType
-from typing import Optional, Union
+from typing import Optional, Union, cast
 
 from . import _ext
 from ._internal import poll_fd
@@ -97,6 +97,7 @@ class Chip:
         longer be used after this method is called.
         """
         self._check_closed()
+        self._chip = cast(_ext.Chip, self._chip)
         self._chip.close()
         self._chip = None
 
@@ -108,6 +109,7 @@ class Chip:
           New gpiod.ChipInfo object.
         """
         self._check_closed()
+        self._chip = cast(_ext.Chip, self._chip)
 
         if not self._info:
             self._info = self._chip.get_info()
@@ -132,6 +134,7 @@ class Chip:
           so - returns it.
         """
         self._check_closed()
+        self._chip = cast(_ext.Chip, self._chip)
 
         if not isinstance(id, int):
             try:
@@ -154,6 +157,7 @@ class Chip:
 
     def _get_line_info(self, line: Union[int, str], watch: bool) -> LineInfo:
         self._check_closed()
+        self._chip = cast(_ext.Chip, self._chip)
         return self._chip.get_line_info(self.line_offset_from_id(line), watch)
 
     def get_line_info(self, line: Union[int, str]) -> LineInfo:
@@ -192,6 +196,7 @@ class Chip:
             Offset or name of the line to stop watching.
         """
         self._check_closed()
+        self._chip = cast(_ext.Chip, self._chip)
         return self._chip.unwatch_line_info(self.line_offset_from_id(line))
 
     def wait_info_event(
@@ -226,6 +231,7 @@ class Chip:
           This function may block if there are no available events in the queue.
         """
         self._check_closed()
+        self._chip = cast(_ext.Chip, self._chip)
         return self._chip.read_info_event()
 
     def request_lines(
@@ -258,6 +264,7 @@ class Chip:
           New LineRequest object.
         """
         self._check_closed()
+        self._chip = cast(_ext.Chip, self._chip)
 
         line_cfg = _ext.LineConfig()
 
@@ -362,6 +369,7 @@ class Chip:
         Filesystem path used to open this chip.
         """
         self._check_closed()
+        self._chip = cast(_ext.Chip, self._chip)
         return self._chip.path
 
     @property
@@ -370,4 +378,5 @@ class Chip:
         File descriptor associated with this chip.
         """
         self._check_closed()
+        self._chip = cast(_ext.Chip, self._chip)
         return self._chip.fd

-- 
2.34.1