@@ -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):
"""
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 <jsnow@redhat.com> --- python/qemu/lib/qmp.py | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)