[Development] Qt modules, API changes and Qt 6
Frederik.Gladhorn at qt.io
Tue Jan 29 10:32:00 CET 2019
Here are the options we discussed internally. I'm happy to elaborate more in
case something is unclear.
1 Do nothing / today / qt5.git
2 Heads: use the latest revision of each branch (the system we used to have in
3 Modules containing pinned dependency sha1s
Each module is completely self-contained, that means qt5 is not
required as such (but may still exist as a collection of all modules, for
convenience and releases). In each module we have a list of dependencies and
Updates for a release (and also otherwise) must happen regularly (e.g.
nightly), moving each module forward towards newer dependencies, this would be
implemented as bot which updates the above mentioned requirements file.
4 Monolithic repository for essentials
Merging at least qtbase and qtdeclarative and probably a whole lot
more into one repository. Likely excluding webengine and webkit.
5 A way to stage breaking changes across modules (updating for example qtbase,
qtdeclarative and qt5.git at the same time)
Presumably do some annotation of the commit message in Gerrit, or
figure out how to connect changes in Gerrit in another way.
I made a small table on the wiki:
1: is where we are today and in my opinion our processes get in our ways
2: we used to have this, it has the problem that some modules are always
failing tests due to their dependencies changing. That's an unfortunate
situation. We want to find out about breakages due to dependencies quickly but
don't want to block development.
3: All modules get the same treatment and it makes things more consistent. At
the same time we really need a bot then that moves modules forward with
respect to their dependencies. We would also want to have a visualization that
shows how much a module is behind e.g. qtbase (in days and number of commits).
We almost had this before in the form of sync.profile where pinning was an
This proposal does the pinning always and will result in a lot of commits that
simply say: bump dependency versions.
4: Requires finding out how to run the CI on this. It's in many ways
attractive, but we would always struggle with defining what's in and what not.
I see Qt also as ecosystem where modules join and sometimes get left behind.
We want to enable that more, so the mono repo approach seems tricky in that
respect. That doesn't prevent deciding on some repos being merged. Merging
between Qt 5 and 6 will then be harder though.
5: This is more of a cludge and could allow staging changes in qtbase and
qtdeclarative at the same time while also trying to update qt5.git. It's a bit
complex and needs people to be very aware of it and will block other changes
from being processed at the same time.
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