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[PATCH RFC 18/32] python//qmp.py: add casts to JSON deserialization
From: |
John Snow |
Subject: |
[PATCH RFC 18/32] python//qmp.py: add casts to JSON deserialization |
Date: |
Thu, 14 May 2020 01:53:49 -0400 |
mypy and python type hints are not powerful enough to properly describe
JSON messages in Python 3.6. The best we can do, generally, is describe
them as Dict[str, Any].
Add casts to coerce this type for static analysis; but do NOT enforce
this type at runtime in any way.
Note: Python 3.8 adds a TypedDict construct which allows for the
description of more arbitrary Dictionary shapes. There is a third-party
module, "Pydantic", which is compatible with 3.6 that can be used
instead of the JSON library that parses JSON messages to fully-typed
Python objects, and may be preferable in some cases.
(That is well beyond the scope of this commit or series.)
Signed-off-by: John Snow <address@hidden>
---
python/qemu/lib/qmp.py | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/python/qemu/lib/qmp.py b/python/qemu/lib/qmp.py
index 0036204218..e460234f2e 100644
--- a/python/qemu/lib/qmp.py
+++ b/python/qemu/lib/qmp.py
@@ -13,6 +13,7 @@
import logging
from typing import (
Any,
+ cast,
Dict,
Optional,
TextIO,
@@ -129,7 +130,10 @@ def __json_read(self, only_event=False):
data = self.__sockfile.readline()
if not data:
return None
- resp = json.loads(data)
+ # By definition, any JSON received from QMP is a QMPMessage,
+ # and we are asserting only at static analysis time that it
+ # has a particular shape.
+ resp = cast(QMPMessage, json.loads(data))
if 'event' in resp:
self.logger.debug("<<< %s", resp)
self.__events.append(resp)
@@ -261,7 +265,7 @@ def command(self, cmd, **kwds):
ret = self.cmd(cmd, kwds)
if 'error' in ret:
raise QMPResponseError(ret)
- return ret['return']
+ return cast(QMPReturnValue, ret['return'])
def pull_event(self, wait=False):
"""
--
2.21.1
- [PATCH RFC 11/32] python/qemu/lib: remove Python2 style super() calls, (continued)
- [PATCH RFC 11/32] python/qemu/lib: remove Python2 style super() calls, John Snow, 2020/05/14
- [PATCH RFC 14/32] python//qmp.py: use True/False for non/blocking modes, John Snow, 2020/05/14
- [PATCH RFC 16/32] python//qmp.py: re-absorb MonitorResponseError, John Snow, 2020/05/14
- [PATCH RFC 15/32] python//qmp.py: Define common types, John Snow, 2020/05/14
- [PATCH RFC 17/32] python//qmp.py: Do not return None from cmd_obj, John Snow, 2020/05/14
- [PATCH RFC 18/32] python//qmp.py: add casts to JSON deserialization,
John Snow <=
- [PATCH RFC 20/32] python//qmp.py: assert sockfile is not None, John Snow, 2020/05/14
- [PATCH RFC 21/32] python//machine.py: remove logging configuration, John Snow, 2020/05/14
- [PATCH RFC 22/32] python//machine.py: Fix monitor address typing, John Snow, 2020/05/14
- [PATCH RFC 23/32] python//machine.py: reorder __init__, John Snow, 2020/05/14