@chuckatkins Please review.

It would be preferable if we could support both Python 2 and Python 3. Especially since older versions of these packages seem to only support Python 2?

@adamjstewart this is part of paraview's transition path to dropping python2 support entirely. Kitware is essentially asserting that python2 is being deprecated in paraview and vtk and as part of that, the spack package will only be supporting python3 moving forward.

@chuckatkins what I'm trying to say is that if the current version of these packages only support Python 3, that's fine. But what about all the older versions? I think it should look something like:

depends_on('python')
depends_on('python@3:', when='@5.6:')
depends_on('python@:2', when='@:5.5')

@adamjstewart That's fair. @danlipsa it should probably be something like this then:

extends('python', when='+python')
depends_on('python@3:', when='@5.6: +python', type=('build', 'link', 'run'))
depends_on('[email protected]:2.8', when='@:5.5.2 +python', type=('build', 'link', 'run'))

The extends will make the paraview python modules available with python instead of just pvpython while the depends_on will manage the versioning.

@chuckatkins Sounds good.

@chuckatkins @adamjstewart Please review.
Chuck, this has the problems I showed you before:
spack spec paraview+python
gives
paraview requires python version 3:, but spec asked for 2.7.16
spack spec [email protected]+python
works.
Even if the first command also choses 5.6.0 as paraview version.

@chuckatkins Should we merge this? At least [email protected] and paraview@develop work. Right now in the develop branch no version works because they all use python2.

Why switch to the vendored libtiff

@chuckatkins I rebase on develop and that error went away - so I removed the internal libtiff.

@danlipsa @chuckatkins, I know you're not asking me but I would be opposed to merging this PR, as it stands, on the basis that it alienates all PV versions less than 5.6.0 when the spec includes +python. Even if the concretizer is broken, I think there is a compromise I propose that will permit the build of downrev versions (I care about v5.5.2 because v5.6.0 contains a bug that is exposed by our production ASC code). If you would be willing to change your package.py line 52:

depends_on('[email protected]:2.8', when='@:5.5+python', type=('build', 'link', 'run'))

into these two lines:

depends_on('python', when='@5.3:5.5+python', type=('build', 'link', 'run'))
depends_on('[email protected]:2.8', when='@:5.2+python', type=('build', 'link', 'run'))

it would permit versions between 5.3 and 5.5 inclusive to be built with any python version (v3 will be required if +osmesa is in the spec). It is well-known that PV does not support python3 before 5.3 so, IMHO, this is the natural break. I am perfectly fine with requiring python3 for versions of [email protected] onward. I beg you, please don't deprecate older versions of PV by pushing this PR through unmodified.

@DarylGrunau I believe #11553 will fix some of these issues so that @5.6: +python+osmesa will build with current meson-based mesa and python 3 and @:5.5 +python+osmesa will build will python 2 and the previous autotools version of mesa. This is currently on hold until that gets resolved.

@chuckatkins Not sure what's wrong with travis - this works on my machine. Any ideas?
I could successfully build paraview 5.6 (with python3) and paraview 5.5.2 (with python2)
@DarylGrunau Can you try this?

@chuckatkins Should we merge this?

Thanks for all the work on this!

@chuckatkins I pushed the workaround. Is this ready?

@danlipsa paraview+python works but paraview+python+osmesa still fails (even though the resulting spec is the same 🙁). I tried creating a separate variant for python and python3 and that seems to work in all cases: chuckatkins@619c8f2

Needs to add:

if '+python' in spec or '+python3' in spec:

In both packages configure args then I think we should should be good to go finally.

Good catch. I'll do that.

@danlipsa looks like travis wasn't reporting. See https://travis-ci.org/spack/spack/jobs/543763846 to fix the flake 8 error. Then I'll merge this once it passes.

@chuckatkins What about now?

Rather than open an issue for this, I just realized that '-DVTK_USE_SYSTEM_MPI4PY:BOOL=%s' % variant_bool('+python+mpi'), needs the python3 variant to be able to work as well. For example, I can't install with python3 because the builtin Paraview 5.6.0 MPI4PY is broken.

So close... So close...

@jrood-nrel Thanks for the report. I'll push a fix shortly.

See #11707 for a fix.