Re: [Qemu-devel] [PATCH 47/56] qjson: Have qobject_from_json() & friends reject empty and blank

[Eric Blake]

On 08/08/2018 07:03 AM, Markus Armbruster wrote:
> The last case where qobject_from_json() & friends return null without
> setting an error is empty or blank input.  Callers:
>
> * block.c's parse_json_protocol() reports "Could not parse the JSON
>    options".  It's marked as a work-around, because it also covered
>    actual bugs, but they got fixed in the previous few commits.

How would you trigger this? I guess that would be by using the 
pseud-json block specification spelled "json:" rather than the usual 
"json:{...}".

> * qobject_input_visitor_new_str() reports "JSON parse error".  Also
>    marked as work-around.  The recent fixes have made this unreachable,
>    because it currently gets called only for input starting with '{'.

Indeed, no triggers to this.

> * check-qjson.c's empty_input() and blank_input() demonstrate the
>    behavior.
>
> * The other callers are not affected since they only pass input with
>    exactly one JSON value or, in the case of negative tests, one error.

As long as sending back-to-back newlines to QMP does not treat the empty 
line as an error, you should be okay. (If sending two newlines in a row 
now results in a {"error":...} response from the server for the blank 
line, then you've regressed).

> Fail with "Expecting a JSON value" instead of returning null, and
> simplify callers.
>
> Signed-off-by: Markus Armbruster <address@hidden>
> ---

Yay for getting rid of the inconsistent error reporting!

Reviewed-by: Eric Blake <address@hidden>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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