[cmake-developers] Work on the graphviz support - compatibility ?

[Alexander Neundorf]

On Monday 07 February 2011, Alexander Neundorf wrote:
> On Sunday 06 February 2011, Eric Noulard wrote:
> > 2011/2/5 Alexander Neundorf <neundorf at kde.org>:
> > > Hi,
> > >
> > > in general we keep cmake as backward compatible as possible, so no
> > > builds are broken.
> > >
> > > In a local branch I have a version of cmake with a small improvement to
> > > the graphviz support in cmake.
> > > It turns the variable GRAPHVIZ_IGNORE_TARGETS from a list of strings
> > > into a list of regular expressions. I.e. everything which was before in
> > > GRAPHVIZ_IGNORE_TARGETS and excluded from the dot-files, is now still
> > > excluded, but now there may be more targets excluded (e.g. for "kio"
> > > now not only "kio" is excluded, but also "kio_ftp" etc.)
> > > Also, with this change, the variable GRAPHVIZ_TARGET_IGNORE_REGEX is
> > > not supported anymore, so targets previously excluded from the
> > > dot-files via this (one) regex are now included.
> > >
> > > Both issues can be fixed by, for the first, putting "^...$" around the
> > > string, and for the second by just putting the regex now into
> > > GRAPHVIZ_IGNORE_TARGETS .
> > >
> > > Strictly speaking, this breaks compatibility regarding the graphviz
> > > support. But, do we care about this ?
> > > * it is and was completely undocumented (will write a wiki page soon)
> > > * the changes don't influence the build itself, so no build can be
> > > broken by this change
> > >
> > > What do you think ?
> >
> > I think that, I didn't even know the existence of this, so I wouldn't
> > care about breaking it :-]
> > Moreover I am basically ok that the breakage of an undocumented feature
> > is not a real breakage.
> >
> > Now may be you can:
> >     1) rename GRAPHVIZ_IGNORE_TARGETS to "CMAKE_GRAPHVIZ_IGNORE_TARGETS"
> >         which is more consistent with other var names.
> >
> >     2) check GRAPHVIZ_IGNORE_TARGETS and GRAPHVIZ_TARGET_IGNORE_REGEX
> >     and issue a WARNING if they are used.
> >
> > 2) may even be unecessary with the new "--warn-unused-vars" option.
> >
> > the baseline is if you break it, then break it ALL there won't be any
> > confusion.
>
> I could also make these variables cache variables.
> That's IMO easier to use and also better discoverable.
> With "GRAPHVIZ_IGNORE_TARGETS" they would be all in the "GRAPHVIZ" subtree,
> with "CMAKE_GRAPHVIZ_IGNORE_TARGETS" they would be all together with the
> other cmake variables in the "CMAKE" subtree.
>
> Being in a "GRAPHVIZ" subtree would make them easier to spot, so maybe I'd
> prefer this. But I don't have a strong opinion.
>
> Other comments ?

I guess this means that backward compatibility is no issue here.

Eric, what do you think about the naming and whether make them cache variables 
or not ?

Alex