rv/rvgen: use context managers for file operations

Replace manual file open and close operations with context managers
throughout the rvgen codebase. The previous implementation used
explicit open() and close() calls, which could lead to resource leaks
if exceptions occurred between opening and closing the file handles.

This change affects three file operations: reading DOT specification
files in the automata parser, reading template files in the generator
base class, and writing generated monitor files. All now use the with
statement to ensure proper resource cleanup even in error conditions.

Context managers provide automatic cleanup through the with statement,
which guarantees that file handles are closed when the with block
exits regardless of whether an exception occurred. This follows PEP
343 recommendations and is the standard Python idiom for resource
management. The change also reduces code verbosity while improving
safety and maintainability.

Signed-off-by: Wander Lairson Costa <wander@redhat.com>
Reviewed-by: Nam Cao <namcao@linutronix.de>
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Link: https://lore.kernel.org/r/20260223162407.147003-7-wander@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>

tools/verification/rvgen/rvgen/automata.py

@@ -91,13 +91,11 @@ class Automata:
         cursor = 0
         dot_lines = []
         try:
-            dot_file = open(self.__dot_path)
+            with open(self.__dot_path) as dot_file:
+                dot_lines = dot_file.read().splitlines()
         except OSError as exc:
             raise AutomataError(exc.strerror) from exc
 
-        dot_lines = dot_file.read().splitlines()
-        dot_file.close()
-
         # checking the first line:
         line = dot_lines[cursor].split()
 

tools/verification/rvgen/rvgen/generator.py

@@ -51,11 +51,8 @@ class RVGenerator:
         raise FileNotFoundError("Could not find the rv directory, do you have the kernel source installed?")
 
     def _read_file(self, path):
-        fd = open(path, 'r')
-
-        content = fd.read()
-
-        fd.close()
+        with open(path, 'r') as fd:
+            content = fd.read()
         return content
 
     def _read_template_file(self, file):
@@ -199,9 +196,8 @@ obj-$(CONFIG_RV_MON_{name_up}) += monitors/{name}/{name}.o
             return
 
     def __write_file(self, file_name, content):
-        file = open(file_name, 'w')
-        file.write(content)
-        file.close()
+        with open(file_name, 'w') as file:
+            file.write(content)
 
     def _create_file(self, file_name, content):
         path = f"{self.name}/{file_name}"