From 0581a83aa2dd16d441c4108dd78f3dff5a21c3a6 Mon Sep 17 00:00:00 2001
From: Kenneth Moreland <kmorel@sandia.gov>
Date: Thu, 16 Jun 2016 10:36:20 -0600
Subject: [PATCH] Directly call python when executing expander.py

On Unix-based systems, you can directly execute a script and the system
will automatically run it through its associated interpreter. However,
on Windows this does not work. You just get an error about the script,
which is just a text file, being an invalid executable.

This was an issue when running pyexpander. Now, Python is called
directly for pyexpander.
---
 CMake/FindPyexpander.cmake      |  5 +++++
 CMake/VTKmCheckPyexpander.cmake | 17 +++++++++++------
 CMake/VTKmMacros.cmake          |  3 ++-
 CMakeLists.txt                  |  4 ++++
 4 files changed, 22 insertions(+), 7 deletions(-)
 mode change 100644 => 100755 CMake/FindPyexpander.cmake
 mode change 100644 => 100755 CMake/VTKmCheckPyexpander.cmake
 mode change 100644 => 100755 CMake/VTKmMacros.cmake
 mode change 100644 => 100755 CMakeLists.txt

diff --git a/CMake/FindPyexpander.cmake b/CMake/FindPyexpander.cmake
old mode 100644
new mode 100755
index f949b454c..e3fe496aa
--- a/CMake/FindPyexpander.cmake
+++ b/CMake/FindPyexpander.cmake
@@ -28,6 +28,11 @@
 # PYEXPANDER_FOUND   - True if pyexpander is found
 # PYEXPANDER_COMMAND - The pyexpander executable
 #
+# Note that on some platforms (such as Windows), you cannot execute a python
+# script directly. Thus, it could be safer to execute the Python interpreter
+# with PYEXPANDER_COMMAND as an argument. See FindPythonInterp.cmake for help
+# in finding the Python interpreter.
+#
 
 find_program(PYEXPANDER_COMMAND expander.py)
 
diff --git a/CMake/VTKmCheckPyexpander.cmake b/CMake/VTKmCheckPyexpander.cmake
old mode 100644
new mode 100755
index 820d7d182..90e5f4a13
--- a/CMake/VTKmCheckPyexpander.cmake
+++ b/CMake/VTKmCheckPyexpander.cmake
@@ -23,9 +23,14 @@
 # version stored in the source code. If the versions are different, an
 # error message is printed with further instructions.
 #
-# To use this script, the CMake variables PYEXPANDER_COMMAND, SOURCE_FILE,
-# and GENERATED_FILE must be defined as the two files to compare. A ".in"
-# is appended to SOURCE_FILE to get the pyexpander input.
+# To use this script, the CMake variables PYTHON_EXECUTABLE PYEXPANDER_COMMAND,
+# SOURCE_FILE, and GENERATED_FILE must be defined as the two files to compare.
+# A ".in" is appended to SOURCE_FILE to get the pyexpander input.
+
+if(NOT PYTHON_EXECUTABLE)
+  message(SEND_ERROR "Variable PYTHON_EXECUTABLE must be set.")
+  return()
+endif()
 
 if(NOT PYEXPANDER_COMMAND)
   message(SEND_ERROR "Variable PYEXPANDER_COMMAND must be set.")
@@ -43,14 +48,14 @@ if(NOT GENERATED_FILE)
 endif()
 
 execute_process(
-  COMMAND ${PYEXPANDER_COMMAND} ${SOURCE_FILE}.in
+  COMMAND ${PYTHON_EXECUTABLE} ${PYEXPANDER_COMMAND} ${SOURCE_FILE}.in
   RESULT_VARIABLE pyexpander_result
   OUTPUT_VARIABLE pyexpander_output
   )
 
-if(${pyexpander_result})
+if(pyexpander_result)
   # If pyexpander returned non-zero, it failed.
-  message(SEND_ERROR "Running pyexpander failed.")
+  message(SEND_ERROR "Running pyexpander failed (${pyexpander_result}).")
   return()
 endif()
 
diff --git a/CMake/VTKmMacros.cmake b/CMake/VTKmMacros.cmake
old mode 100644
new mode 100755
index 960f01964..bfc7895fa
--- a/CMake/VTKmMacros.cmake
+++ b/CMake/VTKmMacros.cmake
@@ -198,10 +198,11 @@ endfunction(vtkm_declare_worklets)
 
 function(vtkm_pyexpander_generated_file generated_file_name)
   # If pyexpander is available, add targets to build and check
-  if(PYEXPANDER_FOUND)
+  if(PYEXPANDER_FOUND AND PYTHONINTERP_FOUND)
     add_custom_command(
       OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${generated_file_name}.checked
       COMMAND ${CMAKE_COMMAND}
+        -DPYTHON_EXECUTABLE=${PYTHON_EXECUTABLE}
         -DPYEXPANDER_COMMAND=${PYEXPANDER_COMMAND}
         -DSOURCE_FILE=${CMAKE_CURRENT_SOURCE_DIR}/${generated_file_name}
         -DGENERATED_FILE=${CMAKE_CURRENT_BINARY_DIR}/${generated_file_name}
diff --git a/CMakeLists.txt b/CMakeLists.txt
old mode 100644
new mode 100755
index b682596bd..dcde002ef
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -207,6 +207,10 @@ if(UNIX AND VTKm_ENABLE_OPENGL_INTEROP)
   find_package(Threads REQUIRED)
 endif()
 
+#-----------------------------------------------------------------------------
+# Find the Python interpreter, which we will use during the build process
+find_package(PythonInterp)
+
 #-----------------------------------------------------------------------------
 # Find Pyexpander in case somebody wants to update the auto generated
 # faux variadic template code