From da96c55a017fbc750b49550c6e7a523dcdab0dbe Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Fri, 22 Dec 2017 11:08:41 +0100
Subject: [PATCH 23/42] qemu.py: make VM() a context manager

RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: <20171222110900.24813-2-stefanha@redhat.com>
Patchwork-id: 78483
O-Subject: [RHV7.5 qemu-kvm-rhev PATCH 01/20] qemu.py: make VM() a context manager
Bugzilla: 1519721
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

There are a number of ways to ensure that the QEMU process is shut down
when the test ends, including atexit.register(), try: finally:, or
unittest.teardown() methods.  All of these require extra code and the
programmer must remember to add vm.shutdown().

A nice solution is context managers:

  with VM(binary) as vm:
      ...
  # vm is guaranteed to be shut down here

Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Message-id: 20170824072202.26818-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit d792bc3811f22a22a46c7d9a725fd29029f54095)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 scripts/qemu.py | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/scripts/qemu.py b/scripts/qemu.py
index 880e3e8..4d8ee10 100644
--- a/scripts/qemu.py
+++ b/scripts/qemu.py
@@ -21,7 +21,14 @@ import qmp.qmp
 
 
 class QEMUMachine(object):
-    '''A QEMU VM'''
+    '''A QEMU VM
+
+    Use this object as a context manager to ensure the QEMU process terminates::
+
+        with VM(binary) as vm:
+            ...
+        # vm is guaranteed to be shut down here
+    '''
 
     def __init__(self, binary, args=[], wrapper=[], name=None, test_dir="/var/tmp",
                  monitor_address=None, socket_scm_helper=None, debug=False):
@@ -40,6 +47,13 @@ class QEMUMachine(object):
         self._socket_scm_helper = socket_scm_helper
         self._debug = debug
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.shutdown()
+        return False
+
     # This can be used to add an unused monitor instance.
     def add_monitor_telnet(self, ip, port):
         args = 'tcp:%s:%d,server,nowait,telnet' % (ip, port)
-- 
1.8.3.1