[libvirt] [Qemu-devel] [PULL 25/26] block: Remove deprecated -drive option serial

[Markus Armbruster]

Thomas Huth <thuth at redhat.com> writes:

> On 10.07.2018 17:24, Peter Krempa wrote:
>> On Tue, Jul 10, 2018 at 17:01:22 +0200, Cornelia Huck wrote:
>>> On Tue, 10 Jul 2018 16:39:31 +0200
>>> Peter Krempa <pkrempa at redhat.com> wrote:
>>>> On Tue, Jul 10, 2018 at 16:22:08 +0200, Cornelia Huck wrote:
>>>>> On Tue, 10 Jul 2018 07:59:15 +0200
>>>>> Markus Armbruster <armbru at redhat.com> wrote:
>> 
>> [...]
>> 
>>>>> "ERROR: 'old_option' is deprecated and will be removed; use 'modern_option' instead"
>>>>>
>>>>> and do an exit(1).
>>>>>
>>>>> Would that be workable?  
>>>>
>>>> For delivering the warnings via monitor you'll need a store that will
>>>> collect all the warnings and prepare them for delivery. You've got
>>>> basically two options:
>>>>
>>>> 1) monitor command to poll for deprecated options
>>>> 2) event with deprecated options
>>>>
>>>> Both require storing them since libvirt connects to the monitor only
>>>> after the command line is processed.
>>>>
>>>> Warnings printed to stderr are nearly useless because until something
>>>> breaks nobody bothers to read the log files.
>>>
>>> So, from that I gather that a hard failure would be the easiest for
>>> libvirt to detect (and everything else would become complicated really
>>> quickly), right?
>> 
>> People start complaining only when stuff breaks. If anything is optional
>> people will usually not enable it. That makes any non-mandatory option
>> not work in most cases.
>
> So would it help if we "invert" the logic, i.e. deprecated_report()
> would do exit(1) by default? Then, if the (human) users still want to
> continue with the deprecated option, they have to add a
> "--ignore-deprecation" command line switch to make QEMU start
> successfully...

You owe the God of Backward Compatibility one rubber chicken for
thinking this heretic thought!