From 5eec9da8fe4386c4ae027dc4e9340e105ebb5391 Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Tue, 19 Jul 2022 13:28:43 -0400
Subject: [PATCH] make search for python libraries consistent with search for
 python interpreter

- apply same semantics of selecting the interpreter than the main cmake script
- make certain that we search for the interpreter first
- when searching for the library find the version matching the interpreter
- error out when library version and interpreter version does not match
---
 cmake/Modules/Packages/MDI.cmake    | 13 +++++++++++++
 cmake/Modules/Packages/PYTHON.cmake | 20 ++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/cmake/Modules/Packages/MDI.cmake b/cmake/Modules/Packages/MDI.cmake
index 1a14d5273a..d873c8f6d1 100644
--- a/cmake/Modules/Packages/MDI.cmake
+++ b/cmake/Modules/Packages/MDI.cmake
@@ -26,8 +26,21 @@ if(DOWNLOAD_MDI)
   # detect if we have python development support and thus can enable python plugins
   set(MDI_USE_PYTHON_PLUGINS OFF)
   if(CMAKE_VERSION VERSION_LESS 3.12)
+    if(NOT PYTHON_VERSION_STRING)
+      set(Python_ADDITIONAL_VERSIONS 3.12 3.11 3.10 3.9 3.8 3.7 3.6)
+      # search for interpreter first, so we have a consistent library
+      find_package(PythonInterp) # Deprecated since version 3.12
+      if(PYTHONINTERP_FOUND)
+        set(Python_EXECUTABLE ${PYTHON_EXECUTABLE})
+      endif()
+    endif()
+    # search for the library matching the selected interpreter
+    set(Python_ADDITIONAL_VERSIONS ${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR})
     find_package(PythonLibs QUIET) # Deprecated since version 3.12
     if(PYTHONLIBS_FOUND)
+      if(NOT (PYTHON_VERSION_STRING STREQUAL PYTHONLIBS_VERSION_STRING))
+        message(FATAL_ERROR "Python Library version ${PYTHONLIBS_VERSION_STRING} does not match Interpreter version ${PYTHON_VERSION_STRING}")
+      endif()
       set(MDI_USE_PYTHON_PLUGINS ON)
     endif()
   else()
diff --git a/cmake/Modules/Packages/PYTHON.cmake b/cmake/Modules/Packages/PYTHON.cmake
index c94db88073..4a2925fe31 100644
--- a/cmake/Modules/Packages/PYTHON.cmake
+++ b/cmake/Modules/Packages/PYTHON.cmake
@@ -1,8 +1,28 @@
 if(CMAKE_VERSION VERSION_LESS 3.12)
+  if(NOT PYTHON_VERSION_STRING)
+    set(Python_ADDITIONAL_VERSIONS 3.12 3.11 3.10 3.9 3.8 3.7 3.6)
+    # search for interpreter first, so we have a consistent library
+    find_package(PythonInterp) # Deprecated since version 3.12
+    if(PYTHONINTERP_FOUND)
+      set(Python_EXECUTABLE ${PYTHON_EXECUTABLE})
+    endif()
+  endif()
+  # search for the library matching the selected interpreter
+  set(Python_ADDITIONAL_VERSIONS ${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR})
   find_package(PythonLibs REQUIRED) # Deprecated since version 3.12
+  if(NOT (PYTHON_VERSION_STRING STREQUAL PYTHONLIBS_VERSION_STRING))
+    message(FATAL_ERROR "Python Library version ${PYTHONLIBS_VERSION_STRING} does not match Interpreter version ${PYTHON_VERSION_STRING}")
+  endif()
   target_include_directories(lammps PRIVATE ${PYTHON_INCLUDE_DIRS})
   target_link_libraries(lammps PRIVATE ${PYTHON_LIBRARIES})
 else()
+  if(NOT Python_INTERPRETER)
+    # backward compatibility
+    if(PYTHON_EXECUTABLE)
+      set(Python_EXECUTABLE ${PYTHON_EXECUTABLE})
+    endif()
+    find_package(Python COMPONENTS Interpreter)
+  endif()
   find_package(Python REQUIRED COMPONENTS Interpreter Development)
   target_link_libraries(lammps PRIVATE Python::Python)
 endif()