Merge pull request #693 from JonathonReinhart/670-serial-close

Override RawIOBase.close() and .closed

serial/serialutil.py

@@ -557,6 +557,16 @@ def readinto(self, b):
             b[:n] = array.array('b', data)
         return n
 
+    def close(self):
+        # Do not call RawIOBase.close() as that will try to flush().
+        pass
+
+    @property
+    def closed(self):
+        # Overrides RawIOBase.closed, as RawIOBase can only be closed once,
+        # but a Serial object can be opened/closed multiple times.
+        return not self.is_open
+
     #  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -
     # context manager
 

test/test_close.py

@@ -0,0 +1,58 @@
+#! /usr/bin/env python
+#
+# This file is part of pySerial - Cross platform serial port support for Python
+# (C) 2001-2015 Chris Liechti <cliechti@gmx.net>
+# (C) 2023 Google LLC
+#
+# SPDX-License-Identifier:    BSD-3-Clause
+import sys
+import unittest
+import serial
+
+# on which port should the tests be performed:
+PORT = 'loop://'
+
+class TestClose(unittest.TestCase):
+
+    def test_closed_true(self):
+        # closed is True if a Serial port is not open
+        s = serial.Serial()
+        self.assertFalse(s.is_open)
+        self.assertTrue(s.closed)
+
+    def test_closed_false(self):
+        # closed is False if a Serial port is open
+        s = serial.serial_for_url(PORT, timeout=1)
+        self.assertTrue(s.is_open)
+        self.assertFalse(s.closed)
+
+        s.close()
+        self.assertTrue(s.closed)
+
+    def test_close_not_called_by_finalize_if_closed(self):
+        close_calls = 0
+
+        class TestSerial(serial.Serial):
+            def close(self):
+                nonlocal close_calls
+                close_calls += 1
+
+        with TestSerial() as s:
+            pass
+            # close() should be called here
+
+        # Trigger RawIOBase finalization.
+        # Because we override .closed, close() should not be called
+        # if Serial says it is already closed.
+        del s
+
+        self.assertEqual(close_calls, 1)
+
+# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+if __name__ == '__main__':
+    if len(sys.argv) > 1:
+        PORT = sys.argv[1]
+    sys.stdout.write("Testing port: {!r}\n".format(PORT))
+    sys.argv[1:] = ['-v']
+    # When this module is executed from the command-line, it runs all its tests
+    unittest.main()