Re: [PATCH 1/1] sphinx/qapidoc: Tidy up pylint warning raise-missing-from

[Markus Armbruster <armbru@redhat.com>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On Fri, 3 Nov 2023 at 03:08, John Snow <jsnow@redhat.com> wrote:
>>
>> On Wed, Oct 25, 2023 at 6:10 AM Markus Armbruster <armbru@redhat.com> wrote:
>> >
>> > Pylint advises:
>> >
>> >     docs/sphinx/qapidoc.py:518:12: W0707: Consider explicitly re-raising using 'raise ExtensionError(str(err)) from err' (raise-missing-from)
>> >
>> > From its manual:
>> >
>> >     Python's exception chaining shows the traceback of the current
>> >     exception, but also of the original exception.  When you raise a
>> >     new exception after another exception was caught it's likely that
>> >     the second exception is a friendly re-wrapping of the first
>> >     exception.  In such cases `raise from` provides a better link
>> >     between the two tracebacks in the final error.
>> >
>> > Makes sense, so do it.
>> >
>> > Signed-off-by: Markus Armbruster <armbru@redhat.com>
>>
>> In this case it probably doesn't make a difference because Sphinx has
>> its own formatting for displaying the errors, but it's good hygiene.
>>
>> Reviewed-by: John Snow <jsnow@redhat.com>
>
> Has somebody checked that the error Sphinx shows to the user
> is still the friendly one? The only reason to raise
> this error is so that Sphinx will catch it and display
> the friendly string, so anything about tracebacks is a red
> herring -- if the traceback is shown to the user then we got
> something wrong.

The exception type doesn't change, only the backtrace stored within the
exception.  Can't see how its catching could be affected.

To be sure, stick a '} at the beginning of qapi-schema.json and run
sphinx-build.  Result:

    Extension error:
    /work/armbru/qemu/docs/../qapi/qapi-schema.json:1:1: expected '{', '[', string, or boolean

Satisfied?