On Fri, 25 Sep 2015 12:43:55 +0200 Victor Berger <victor.ber...@polytechnique.org> wrote:
> On 2015-09-25 12:25, Nils Chr. Brause wrote : > > Hi, > > > > On Fri, Sep 25, 2015 at 10:52 AM, Victor Berger > > <victor.ber...@polytechnique.org> wrote: > >> The questions about how breaking evolutions will be handled need to be > >> specified as well: how should an old scanner behave when it encounters > >> a > >> more recent protocol file, containing fields or attributes it does not > >> recognize ? Ignore them ? Fail and declare being "not compatible with > >> this > >> protocol format, please upgrade" ? > > > > The last one makes the most sense to me. Someone who develops a > > language binding should always keep her/his scanner up to date with the > > most recent XML file format. > > Agreed... This fails if someone is stuck with an old version of libwayland and the scanner, e.g. due to policy or proprietary software reasons, and wants to use a recent third party XML. They are not good reasons... But since I believe that wayland-scanner already ignores unknown attributes, there is no problem. We cannot retroactively change old scanners anyway. > > [...] > > Also, from the discussion last year it emerged that the scanner should > > also be > > modified to at least check for the validity of the new attribues. > > You can find the work that I had done so far here: > > https://github.com/NilsBrause/Wayland/commits/xml > > ... but from the discussion I had with pq on IRC, it does not seem like > having the C-scanner start rejecting "old" protocol files is a welcomes > outcome, from they point of view. Yes. Let's not break existing users, be that old XML files or old scanners. > However, maybe checking the file, and emitting warnings if it is in an > old format could be an option ? > > The other bindings could explicitly refuse old formats, I don't think > it's a deal breaker either. Did you just swap the scenario here? How can you even detect old XML files? The proposals so far do not include anything for that, and I don't think it should even be an issue. Adding an XML language version might be possible, but is it necessary? Thanks, pq
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