[PATCH 31/42] scripts/qmp-shell: Use context manager instead of atexit

[John Snow]

We can invoke the shell history writing when we leave the QMPShell scope
instead of relying on atexit. Doing so may be preferable to avoid global
state being registered from within a class instead of from the
application logic directly.

Use QMP's context manager to hook this history saving at close time,
which gets invoked when we leave the context block.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 scripts/qmp/qmp-shell | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/scripts/qmp/qmp-shell b/scripts/qmp/qmp-shell
index f14fe211cc..ec028d662e 100755
--- a/scripts/qmp/qmp-shell
+++ b/scripts/qmp/qmp-shell
@@ -66,7 +66,6 @@
 # sent to QEMU, which is useful for debugging and documentation generation.
 import argparse
 import ast
-import atexit
 import json
 import os
 import re
@@ -142,6 +141,11 @@ class QMPShell(qmp.QEMUMonitorProtocol):
         self.pretty = pretty
         self.verbose = verbose
 
+    def close(self) -> None:
+        # Hook into context manager of parent to save shell history.
+        self._save_history()
+        super().close()
+
     def _fill_completion(self) -> None:
         cmds = self.cmd('query-commands')
         if 'error' in cmds:
@@ -164,9 +168,8 @@ class QMPShell(qmp.QEMUMonitorProtocol):
             pass
         except IOError as err:
             print(f"Failed to read history '{self._histfile}': {err!s}")
-        atexit.register(self.__save_history)
 
-    def __save_history(self) -> None:
+    def _save_history(self) -> None:
         try:
             readline.write_history_file(self._histfile)
         except IOError as err:
@@ -448,25 +451,25 @@ def main() -> None:
         parser.error("QMP socket or TCP address must be specified")
 
     shell_class = HMPShell if args.hmp else QMPShell
+
     try:
         address = shell_class.parse_address(args.qmp_server)
     except qmp.QMPBadPortError:
         parser.error(f"Bad port number: {args.qmp_server}")
         return  # pycharm doesn't know error() is noreturn
 
-    qemu = shell_class(address, args.pretty, args.verbose)
+    with shell_class(address, args.pretty, args.verbose) as qemu:
+        try:
+            qemu.connect(negotiate=not args.skip_negotiation)
+        except qmp.QMPConnectError:
+            die("Didn't get QMP greeting message")
+        except qmp.QMPCapabilitiesError:
+            die("Couldn't negotiate capabilities")
+        except OSError as err:
+            die(f"Couldn't connect to {args.qmp_server}: {err!s}")
 
-    try:
-        qemu.connect(negotiate=not args.skip_negotiation)
-    except qmp.QMPConnectError:
-        die("Didn't get QMP greeting message")
-    except qmp.QMPCapabilitiesError:
-        die("Couldn't negotiate capabilities")
-    except OSError as err:
-        die(f"Couldn't connect to {args.qmp_server}: {err!s}")
-
-    for _ in qemu.repl():
-        pass
+        for _ in qemu.repl():
+            pass
 
 
 if __name__ == '__main__':
-- 
2.31.1