[yocto] [PATCH] bb.build.addtask: add simple check for circular dependency

[Richard Purdie]

On Fri, 2019-01-18 at 15:16 +0100, Ulf Samuelsson wrote:
> > 18 jan. 2019 kl. 12:29 skrev Richard Purdie <
> > richard.purdie at linuxfoundation.org>:
> > 
> > > On Fri, 2019-01-18 at 05:30 +0100, Ulf Samuelsson wrote:
> > > So if KNOWN_TASKS is defined in a configuration file in oe-core,
> > > it
> > > would be OK?
> > > It needs to be extended to check for KNOWN_TASKS == None of
> > > course.
> > 
> > No, this is too fragile. We then have to maintain two different
> > lists
> > of tasks. If we did that we may as well just remove the generic
> > tasks
> > mechanism and hardcode the tasks list in the metadata.
> > 
> Why do we need two lists?

If we change one of these "generic" tasks, we then need to remember to
also update KNOWN_TASKS. The same information is being encoded in two
places.

Maintaining the same information in two different places means one of
those places inevitably ends up out of date.

> We need to know in what order the generic tasks are executed, that is
> all.
> 
> Then we need to see if an addtask is violating that order.
> If the ”after” or ”before” is not a generic task, the check cannot
> catch that.
> 
> If the user decides to not use the generic tasks, and create new ones
> with the same name, as the generic tasks, but rearranges the order,
> there will be a problem, but I do not see any other problems.
> 
> Please enlighten me!

This has the problem that the code will find some subset of the bugs
but not all of them. We'll then get users reporting that the tests
failed and asking for the checks to be improved.

So no, we are not doing this, sorry.

Cheers,

Richard