"Distribution tasks with corresponding series tasks may only be retargeted to a different package."

Asked by Christopher M. Peñalver on 2018-09-01

I'm attempting to twiddle:

Distirbution: Fedora

Distribution: Ubuntu

and get error message:
There is 1 error in the data you entered. Please fix it and try again.
Distribution tasks with corresponding series tasks may only be retargeted to a different package.

I've not had problems making this exact change in the past.

Hence, my questions:
1) Is this actually a permissions issue or a one-off issue with Launchpad Itself?
2) If permissions, what permission set, bit, etc. does one need to make this change?

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Solved by:
Colin Watson
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Best Colin Watson (cjwatson) said : #1

It is neither a permissions issue nor a one-off issue. This restriction has been in place since 2011. You probably only think you've made the exact same change in the past, because the way multiple tasks interact here is not very intuitive.

The problem is that series tasks on packages (like the Ubuntu/quantal xserver-xorg-video-ati task) are defined in a very strange way: they affect all tasks on the distribution in question. This means that, even though it doesn't seem as though it should be affected by that other task, changing the Fedora xorg task's distribution from Fedora to Ubuntu would require Launchpad to create an additional task for Ubuntu/quantal xorg, which would be a very strange thing to do when you just changed a task's target. Launchpad therefore refuses to make this transition.

Ideally, I'd rather that series tasks weren't defined in this way: I think it would be clearer if you only targeted tasks for a single source package to a series, rather than targeting all the tasks on a distribution at once, and then we wouldn't need to have this strange restriction on target transitions. But that would be a big and complex change.

As it stands, the simplest thing for you to do is just to mark the Fedora xorg task invalid (as you've done) and then use "Also affects distribution/package" to create a new bug task as appropriate.

Colin Watson, thanks for the *fast* and concise root cause! I'll watch out for this in the future, and your suggested solution works for me.