Il ven 30 gen 2026, 14:00 Markus Armbruster <[email protected]> ha scritto:
> > Another benefit is that QEMU can report the first parsing error
> > immediately, without waiting for delimiters to be balanced.
>
> Sounds promising! Let's see...
>
> Before the series:
>
> $ socat "READLINE,prompt=QMP> "
> UNIX-CONNECT:$HOME/work/images/test-qmp
> {"QMP": {"version": {"qemu": {"micro": 50, "minor": 2, "major": 10},
> "package": "v10.2.0-567-gfb6b66de43-dirty"}, "capabilities": ["oob"]}}
> QMP> [{"a"]
>
> Parse error not diagnosed right away, but ...
>
> QMP> }
> {"error": {"class": "GenericError", "desc": "JSON parse error, missing
> : in object pair"}}
>
> .... only when the streamer decides the expression is complete.
>
> After the series:
>
> QMP> [{"a"]
> {"error": {"class": "GenericError", "desc": "JSON parse error at line
> 1, column 6, expecting ':'"}}
>
> Cool! However, if I do it again, things fall apart:
>
> QMP> [{"a"
> QMP> }
> QMP> }
> QMP> }
> QMP> ]
> QMP> ]
> {"error": {"class": "GenericError", "desc": "JSON parse error at line
> 7, column 1, expecting value"}}
>
> Parse error recovery not quite right?
>
Well, if you read the above very carefully :) the error is *reported*
immediately, but recovery still waits for delimiters to be balanced.
In testing, when I got an error I just typed a long enough variant on
"]}]}]}" and that is enough to recover—just like in the old parser. Still
the difference in error reporting matters, because it gives feedback that
is immediately useful, rather than possibly delayed forever.
The policy is easy to change, either in v2 or in subsequent work, because
recovery is layered on top of json-parser and its code is nothing more than
"if you believe it's a good time to recover, reset the parser".
Paolo
> On top of the benefits intrinsic in the push architecture, it so happens
> > that it's really easy to add a location to JSON parsing errors now, so
> > do that as well.
> >
> > Paolo
>
>
