Ok, so let's abandon this approach and reconsider our options (see also update to b.k.o bug report)

Update commit message to track corresponding kdesrc-build issue in Gitlab on invent.kde.org

Hmm, doing this produces a dependency cycle when you *don't* include qt5-build-include through your kdesrc-build.rc. E.g.: kdesrc-build --include-dependencies --no-metadata kio explodes with:

Fixed up commit message/bug tag.

Rework absPathToExecutable

Rebased git history to get proper tags in commit messages.

With the last change bug #404486 should be fully fixed.

• Consider and prefer using tools from qtdir/bin and kdedir/bin if available.

The only thing missing is to adjust Util & Application modules, specifically the sub _checkForEssentialBuildPrograms in Application to consider qtdir/kdedir as well as $PATH (absPathToExecutable).
Possibly using a copy of the absPathToExecutable which takes an additional second @paths positional argument (list).

• Include qtdir when adjusting build context environment (variables)

A way to detect the distro and running version

Some clean up work to remove QtDebug include from sudokuboard.h

Port pretty printing of board contents to qCDebug().

In that case, maybe you'd simply want to flip the default value of the setting "When printing, try to fit more than one puzzle on a page" instead?
That way ksudoku will print just the one puzzle, wasting paper, but it will print it right away.

I take it you mean you want a different UX for the printing feature. Something more like the following, perhaps?

This is mainly a first attempt to get the ball rolling. It kills off nearly all of the previously remaining dbo* statements with one fell swoop of Search & Replace.

Use KMessageBox::sorry() instead of KMessageBox::information() type message boxes.

In D5671#106253, @ltoscano wrote:

The real test could be probably a unit test :)

Provide feedback to the user when unable to start a puzzle of a particular (invalid) game variant.

Rebased.

This change has landed.

Removed the contains() check, which I believe to be entirely redundant.

I think it's safe to skip the contains() check entirely, and I'm tempted to remove it. Did I overlook something?

Working on a Differential for this right now.

Looks good to me!

In D5627#105882, @stikonas wrote:

I think the QString shouldn't be const. We want to modify it inside load.

In D5627#105879, @ltoscano wrote:

Do we really need the auto pointer? (just to check if that would bump some requirement, maybe just for one usage is not needed)

In D5627#105875, @ltoscano wrote:

I wonder if instead of all the if (), can't we just change the signatures to pass a real QString reference instead of a pointer?

In D5627#105796, @ltoscano wrote:

unless loadCustomShapeFromPath does something more

It does appear to be unused, OTOH its purpose appears to be to allow people to import new game variant types (shapes).
Logically that should have been wired up to a Get Hot New Stuff button/dialog for people to exchange custom puzzle variants.
Is that a feature we'd like to offer?

Looks good to me. Let's see what tosky thinks.

I've added a few more comments. Before landing this change please review the one on copyright in particular, as I'm not certain the way a few copyright statements were consolidated is sound (or rather that the implications are what was intended).

In D5627#105389, @ltoscano wrote:

Non-core sudokus are not loaded ("Unable to download file.") and then the program crash:

[KCrash Handler]
#6  0x000055b4c9440908 in QVector<int>::size() const ()
#7  0x000055b4c944f6a0 in ksudoku::Puzzle::hasSolution() const ()
#8  0x000055b4c945fafb in ksudoku::WelcomeScreen::generatePuzzle() ()
#9  0x000055b4c9460ebd in QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, void (ksudoku::WelcomeScreen::*)()>::call(void (ksudoku::WelcomeScreen::*)(), ksudoku::WelcomeScreen*, void**) ()
#10 0x000055b4c9460e4f in void QtPrivate::FunctionPointer<void (ksudoku::WelcomeScreen::*)()>::call<QtPrivate::List<>, void>(void (ksudoku::WelcomeScreen::*)(), ksudoku::WelcomeScreen*, void**) ()
#11 0x000055b4c9460d5b in QtPrivate::QSlotObject<void (ksudoku::WelcomeScreen::*)(), QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase*, QObject*, void**, bool*) ()

There may be other issues.

Looks basically sane, don't have enough knowledge of the real inner workings of ksudoku to offer much more feedback than this on the proposed changes.

Incorporate stikonas's suggestions.

Fix: crash on opening a custom game variant.

Thanks for the pointer. I'm still now sure why ksudoku would crash because at worst the puzzle should be in some 'invalid' state with bogus contents ... but then the QVector should still return a proper size() without crashing.
Alternatively, possibly more likely, the memory management of the containing Puzzle object itself was already messed up and the change in code merely tickles the bug.

Fixes to make it compile.

Rebased onto latest frameworks.