[PATCH wayland v2] Remove protocol/wayland.dtd

[Pekka Paalanen]

On Mon, 19 Oct 2015 11:30:47 +1000
Peter Hutterer <peter.hutterer at who-t.net> wrote:

> On Fri, Oct 16, 2015 at 11:42:21AM +0300, Pekka Paalanen wrote:
> > On Fri, 16 Oct 2015 12:29:11 +1000
> > Peter Hutterer <peter.hutterer at who-t.net> wrote:
> > 
> > > On Fri, Oct 09, 2015 at 01:16:49PM +0200, Nils Chr. Brause wrote:
> > > > Hi,
> > > > 
> > > > Reviewed-by: Nils Christopher Brause <nilschrbrause at googlemail.com>
> > > > 
> > > > I ran distcheck and it worked. :)
> > > 
> > > a bit late, but I would like to register my disagreement with this patch :)
> > > 
> > > Having the DTD is a much simpler and less bug-prone description of what the
> > > protocol should look like. Having the scanner define the protocol means the
> > > protocol is whatever the current version of the scanner supports, which is
> > > not a good contract.
> > 
> > Hi Peter,
> > 
> > can't argue with that. It's just that the DTD was unused since
> > 6292fe2af6a45decb7fd39090e74dd87bc4e22b2, Feb 2014.
> > 
> > > I'd argue for reverting this and fixing any mismatch if there is one. And
> > > using the DTD to validate before the scanner even runs.
> > 
> > We talked in IRC about this, and came to the conclusion that maybe we
> > could have wayland-scanner invoke a validity checker against a DTD or
> > an XSD.
> 
> I played around with that. As a quick basic solution we can hook validation
> with libxml2 into the scanner and print a warning if the xml doesn't
> validate. That's less than 50 LOC and won't break things since it doesn't
> touch the actual parsing. and it won't break existing protocols that use
> "creative" tags, all it will do is warn, not fail. See the diff below (after
> reverting 06fb8bd37.
> 
> it's an ugly solution though, but without scanner tests probably the best
> thing we can do.

Yeah, I agree. I think I'd be ok going forward with this. The patch
looks like a good start if we can solve the DTD file loading.

Libxml2 dependency should probably be build-time optional so far.

> > If the original objection to a DTD was because it required manually
> > writing a lint phase in every project build system using the XML files,
> > then having wayland-scanner invoke the check automatically solves that.
> 
> the question that remains though is: the dtd must be an external file for
> extensions to be validated. Which means we need to either pass the dtd as
> argument to the scanner (requires makefile changes everywhere), or we
> hardcode the path into wayland-scanner (issues with running the scanner from
> within the source tree) or we add it as variable to pkgconfig (requires
> makefile changes again). any other solutions to fix this are welcome.
> even if all we do is call out to xmllint we still run into that issue.

Or, hopefully we can embed the DTD file into the scanner binary - is
there no way to let libxml2 read it as a plain string?

I used the following trick to embed some files in Wesgr:
https://github.com/ppaalanen/wesgr/commit/02a840cb7db7eeb80071a353f66865d729738ae5


Thanks,
pq
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