New Framework Review: KDAV

[Volker Krause]

The remaining issues that didn't change ABI anymore (movable value types, hide 
private methods/slots inside the private classes, etc) have long since been 
addressed.

I think there's two possible time slots to actually execute the move to 
frameworks now:
* ASAP, for the June release.
* For the July release, just in time for the 20.08 dependency freeze.

Opinions?

Thanks,
Volker

On Saturday, 4 April 2020 17:32:19 CEST Volker Krause wrote:
> Thanks for the review! We are cutting it close again with the 20.04
> deadline, but fortunately most of these findings aren't ABI-breaking :)
> 
> The result was discussed in more detail at the (virtual) PIM sprint, summary
> below for the record.
> 
> On Saturday, 4 April 2020 16:20:21 CEST Kevin Ottens wrote:
> > Hello,
> > 
> > On Saturday, 9 November 2019 12:33:54 CEST Volker Krause wrote:
> > > during Akademy there was a request to promote KDAV from KDE PIM to
> > > Frameworks for use by Plasma Mobile. KDAV is a framework that implements
> > > the CalDav/ CardDav/GroupDav protocol on top of KIO's WebDav support. It
> > > would be classified as a functional tier 3 framework.
> > > 
> > > So far we have fixed a number of obvious ABI-compatibility issues,
> > > removed
> > > QtXml[Patterns] usage from the public interface and relicensed GPL parts
> > > (apart from a bit of test code) to LGPL. The next step would be a more
> > > thorough review to identify changes necessary before becoming a
> > > Framework.
> > > 
> > > To avoid the last minute invasive changes we ended up doing for
> > > KCalendarCore, I'd propose the following timeline:
> > > 
> > > - identify and implement all necessary changes to the API and ABI until
> > > the
> > > 20.04 Application release (that includes the still necessary move to the
> > > KF5 library namespace).
> > 
> > I'm likely late to the party, but here is what I found by looking at KDAV
> > 
> > master today (first day of the KDE PIM sprint):
> >  * There's a few private methods or Q_SLOTS that I'd hide completely by
> > 
> > moving them to the d-pointer, for the slots we're using type safe connects
> > so they don't even need to be marked as slots at all;
> 
> Cosmetic with no ABI impact, we can do that post 20.04 still.
> 
> >  * Is it worth making DavCollection moveable? It's only copyable right
> >  now;
> 
> Probably yes, that's new API with no ABI break, so we can do that post 20.04
> as well.
> 
> >  * We might want to do something about "ctag" in DavCollection it's a bit
> > 
> > obscure as a name (and the API doc doesn't help), also it seems to not be
> > an official standard (while being widely supported) and there's the
> > sync-token mechanism which has a RFC (RFC6578);
> 
> I have no idea what ctag is (I am only doing the technical work needed to
> turn this into a framework, I didn't write this library).
> 
> >  * Why isn't DavCollectionModifyJob using DavCollection somehow? (might
> >  just
> > 
> > be my ignorance but I find it surprising that it is solely based on a
> > property mechanism);
> 
> I think this is to be able to control which properties get changed, rather
> than sending the full set of them.
> 
> >  * DavCollections(Multi)FetchJob has a mysterious "protocol" parameter on
> > 
> > its collectionDiscovered signal, is it really necessary? if it has to
> > stay,
> > shouldn't be at least documented? or at least a safer type than int?
> 
> Fixed in https://phabricator.kde.org/D28564 and https://phabricator.kde.org/
> D28566
> 
> > * DavCollectionsMultiFetchJob is inconsistent as it's not using
> > Q_DECLARE_PRIVATE;
> 
> That's due to using KJob as a base directly.
> 
> Subsequent discussion suggested this should be a KCompositeJob, David is
> taking care of this.
> 
> >  * KDAV::Error would benefit from more apidox;
> 
> Yes, not blocked by the 20.04 freeze though.
> 
> >  * Is it worth making DavItem moveable? It's only copyable right now;
> 
> See above, same as DavCollection.
> 
> >  * Same comment about etag for DavItem than the ctag one for DavCollection
> 
> See above, same as ctag.
> 
> >  * I'd be tempted to move all the protected methods of DavJobBase on its
> >  d-
> > 
> > pointer, the job subclasses would have access to them anyway, it'd make
> > sense to put them protected in the header only if we expect subclasses
> > outside of the lib (and I doubt this is actually supported);
> 
> ABI impact mitigated by https://phabricator.kde.org/D28562 so we can clean
> this up after 20.04.
> 
> >  * It needs to decide between Qt smart pointers or STL ones I think, found
> >  a
> > 
> > bit of both so far (I'd lean toward STL ones but maybe that's just me);
> 
> Also fixed by https://phabricator.kde.org/D28562.
> 
> > * Make DavUrl moveable?
> 
> See above, same as DavCollection and DavItem.
> 
> >  * EtagCache probably shouldn't have anything protected, also, why is it a
> > 
> > QObject at all?
> 
> This is why:
> https://lxr.kde.org/source/kde/pim/kdepim-runtime/resources/dav/
> resource/akonadietagcache.cpp
> 
> >  * Are we sure we want to return a QLatin1String in ProtocolInfo? this
> > 
> > strike me as an odd choice.
> 
> Fixed in https://phabricator.kde.org/D28563.
> 
> > Overall apidox would likely need a big pass of cleanups as well.
> > 
> > I think that's it from me.
> 
> I hope we managed to address everything on short notice that would require
> ABI breaks after the 20.04 release (and thus cause a delay of the
> frameworks move Volker