[libgpiod][PATCH 04/14] bindings: python: setup: use a context manager to manage files

[Vincent Fazio <vfazio@gmail.com>]

Previously, a number of places in setup.py did not use a context manager
to manage the lifetime of the underlying file descriptor for reading and
writing the `libgpiod-version.txt` file.

While the previous method works, it relies on the returned file object
being assigned to a temporary Python object that has its refcount
decremented immediately after statement execution. This then relies on
the file object's finalizer to close the underlying handle which can
emit ResourceWarnings:

  /bindings/python/setup.py:193: ResourceWarning: unclosed file <_io.TextIOWrapper name='libgpiod-version.txt' mode='w' encoding='UTF-8'>
    open("libgpiod-version.txt", "w").write(LIBGPIOD_VERSION)

Now, we specifically use a context manager to close the file descriptor
when done to explicitly manage its lifetime.

Signed-off-by: Vincent Fazio <vfazio@gmail.com>
---
 bindings/python/setup.py | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/bindings/python/setup.py b/bindings/python/setup.py
index 7c9a03f..4297615 100644
--- a/bindings/python/setup.py
+++ b/bindings/python/setup.py
@@ -87,10 +87,11 @@ def fetch_tarball(func: Callable[[T], None]) -> Callable[[T], None]:
         # If the version in "libgpiod-version.txt" already matches our
         # requested tarball, then skip the fetch altogether.
         try:
-            if open("libgpiod-version.txt").read() == LIBGPIOD_VERSION:
-                log.info("skipping tarball fetch")
-                func(cmd)
-                return
+            with open("libgpiod-version.txt") as f:
+                if f.read() == LIBGPIOD_VERSION:
+                    log.info("skipping tarball fetch")
+                    func(cmd)
+                    return
         except OSError:
             pass
 
@@ -185,7 +186,8 @@ def fetch_tarball(func: Callable[[T], None]) -> Callable[[T], None]:
                     cmd.distribution.metadata.license_files = [LICENSE_FILE]  # type: ignore[attr-defined]
 
         # Save the libgpiod version for sdist
-        open("libgpiod-version.txt", "w").write(LIBGPIOD_VERSION)
+        with open("libgpiod-version.txt", "w") as f:
+            f.write(LIBGPIOD_VERSION)
 
         # Run the command
         func(cmd)
@@ -217,7 +219,8 @@ class build_ext(orig_build_ext):
         # Try to get the gpiod version from the .txt file included in sdist
         libgpiod_version: str | None
         try:
-            libgpiod_version = open("libgpiod-version.txt").read()
+            with open("libgpiod-version.txt") as f:
+                libgpiod_version = f.read()
         except OSError:
             libgpiod_version = LIBGPIOD_VERSION
 
-- 
2.43.0