ParaView: Allow all ParaView versions to depend on Python 2 (#17484)

* Allow all ParaView versions to depend on Python 2

* Keep conflict for 5.9 and up with python 2

* Fix line too long

* Don't use backslash

* Try fixing indent

* Clean logic for python cmake flags

* Try fixing indent

var/spack/repos/builtin/packages/paraview/package.py

@@ -51,7 +51,8 @@ class Paraview(CMakePackage, CudaPackage):
             description='Use module kits')
 
     conflicts('+python', when='+python3')
-    conflicts('+python', when='@5.6:')
+    # Python 2 support dropped with 5.9.0
+    conflicts('+python', when='@5.9:')
     conflicts('+python3', when='@:5.5')
     conflicts('+shared', when='+cuda')
     # Legacy rendering dropped in 5.5
@@ -110,6 +111,11 @@ class Paraview(CMakePackage, CudaPackage):
     depends_on('zlib')
     depends_on('cmake@3.3:', type='build')
 
+    # Can't contretize with python2 and py-setuptools@45.0.0:
+    depends_on('py-setuptools@:44.99.99', when='+python')
+    # Can't contretize with python2 and py-pillow@7.0.0:
+    depends_on('py-pillow@:6', when='+python')
+
     patch('stl-reader-pv440.patch', when='@4.4.0')
 
     # Broken gcc-detection - improved in 5.1.0, redundant later
@@ -232,13 +238,20 @@ def nvariant_bool(feature):
                 '-DPARAVIEW_QT_VERSION=%s' % spec['qt'].version[0],
             ])
 
+        # CMake flags for python have changed with newer ParaView versions
+        # Make sure Spack uses the right cmake flags
         if '+python' in spec or '+python3' in spec:
+            py_use_opt = 'USE' if spec.satisfies('@5.8:') else 'ENABLE'
+            py_ver_opt = 'PARAVIEW' if spec.satisfies('@5.7:') else 'VTK'
+            py_ver_val = 3 if '+python3' in spec else 2
             cmake_args.extend([
-                '-DPARAVIEW_ENABLE_PYTHON:BOOL=ON',
+                '-DPARAVIEW_%s_PYTHON:BOOL=ON' % py_use_opt,
                 '-DPYTHON_EXECUTABLE:FILEPATH=%s' %
                 spec['python'].command.path,
-                '-DVTK_USE_SYSTEM_MPI4PY:BOOL=%s' % variant_bool('+mpi')
+                '-DVTK_USE_SYSTEM_MPI4PY:BOOL=%s' % variant_bool('+mpi'),
+                '-D%s_PYTHON_VERSION:STRING=%d' % (py_ver_opt, py_ver_val)
             ])
+
         else:
             cmake_args.append('-DPARAVIEW_ENABLE_PYTHON:BOOL=OFF')