Merge pull request pyserial#240 from AmberAussie/master

serial: SerialBase with is idempotent

Author: zsquareplusc

serial/serialutil.py

@@ -557,6 +557,8 @@ def readinto(self, b):
     # context manager
 
     def __enter__(self):
+        if not self.is_open:
+            self.open()
         return self
 
     def __exit__(self, *args, **kwargs):

test/test_context.py

@@ -0,0 +1,49 @@
+#! /usr/bin/env python
+#
+# This file is part of pySerial - Cross platform serial port support for Python
+# (C) 2017 Guillaume Galeazzi <[email protected]>
+#
+# SPDX-License-Identifier:    BSD-3-Clause
+"""\
+Some tests for the serial module.
+Part of pySerial (http://pyserial.sf.net)  (C)2001-2011 [email protected]
+
+Intended to be run on different platforms, to ensure portability of
+the code.
+
+Cover some of the aspects of context managment
+"""
+
+import unittest
+import serial
+
+# on which port should the tests be performed:
+PORT = 'loop://'
+
+
+class Test_Context(unittest.TestCase):
+    """Test context"""
+
+    def setUp(self):
+        # create a closed serial port
+        self.s = serial.serial_for_url(PORT)
+
+    def tearDown(self):
+        self.s.close()
+
+    def test_with_idempotent(self):
+        with self.s as stream:
+            stream.write(b'1234')
+
+        # do other stuff like calling an exe which use COM4
+
+        with self.s as stream:
+            stream.write(b'5678')
+
+
+if __name__ == '__main__':
+    import sys
+    sys.stdout.write(__doc__)
+    sys.argv[1:] = ['-v']
+    # When this module is executed from the command-line, it runs all its tests
+    unittest.main()