FindPython: enhance multiple major versions lookup

Modules/FindPython.cmake

@@ -144,18 +144,19 @@ else()
   set (Python_FIND_QUIETLY TRUE)
   set (Python_FIND_REQUIRED FALSE)
 
-  foreach (_Python_REQUIRED_VERSION_MAJOR IN ITEMS 3 2)
+  set (_Python_REQUIRED_VERSIONS 3 2)
+  set (_Python_REQUIRED_VERSION_LAST 2)
+
+  foreach (_Python_REQUIRED_VERSION_MAJOR IN LISTS _Python_REQUIRED_VERSIONS)
     set (Python_FIND_VERSION ${_Python_REQUIRED_VERSION_MAJOR})
     include (${CMAKE_CURRENT_LIST_DIR}/FindPython/Support.cmake)
-    if (Python_FOUND)
+    if (Python_FOUND OR
+        _Python_REQUIRED_VERSION_MAJOR EQUAL _Python_REQUIRED_VERSION_LAST)
       break()
     endif()
     # clean-up some CACHE variables to ensure look-up restart from scratch
-    foreach (_Python_ITEM IN ITEMS EXECUTABLE COMPILER
-                                   LIBRARY_RELEASE RUNTIME_LIBRARY_RELEASE
-                                   LIBRARY_DEBUG RUNTIME_LIBRARY_DEBUG
-                                   INCLUDE_DIR)
-      unset (Python_${_Python_ITEM} CACHE)
+    foreach (_Python_ITEM IN LISTS _Python_CACHED_VARS)
+      unset (${_Python_ITEM} CACHE)
     endforeach()
   endforeach()
 

Modules/FindPython/Support.cmake

@@ -162,12 +162,14 @@ unset (${_PYTHON_PREFIX}_VERSION_MINOR)
 unset (${_PYTHON_PREFIX}_VERSION_PATCH)
 
 unset (_${_PYTHON_PREFIX}_REQUIRED_VARS)
+unset (_${_PYTHON_PREFIX}_CACHED_VARS)
 
 
 # first step, search for the interpreter
 if ("Interpreter" IN_LIST ${_PYTHON_PREFIX}_FIND_COMPONENTS)
   if (${_PYTHON_PREFIX}_FIND_REQUIRED_Interpreter)
     list (APPEND _${_PYTHON_PREFIX}_REQUIRED_VARS ${_PYTHON_PREFIX}_EXECUTABLE)
+    list (APPEND _${_PYTHON_PREFIX}_CACHED_VARS ${_PYTHON_PREFIX}_EXECUTABLE)
   endif()
 
   set (_${_PYTHON_PREFIX}_HINTS "${${_PYTHON_PREFIX}_ROOT_DIR}" ENV ${_PYTHON_PREFIX}_ROOT_DIR)
@@ -305,6 +307,7 @@ endif()
 if ("Compiler" IN_LIST ${_PYTHON_PREFIX}_FIND_COMPONENTS)
   if (${_PYTHON_PREFIX}_FIND_REQUIRED_Compiler)
     list (APPEND _${_PYTHON_PREFIX}_REQUIRED_VARS ${_PYTHON_PREFIX}_COMPILER)
+    list (APPEND _${_PYTHON_PREFIX}_CACHED_VARS ${_PYTHON_PREFIX}_COMPILER)
   endif()
 
   # IronPython specific artifacts
@@ -393,6 +396,12 @@ if ("Development" IN_LIST ${_PYTHON_PREFIX}_FIND_COMPONENTS
   if (${_PYTHON_PREFIX}_FIND_REQUIRED_Development)
     list (APPEND _${_PYTHON_PREFIX}_REQUIRED_VARS ${_PYTHON_PREFIX}_LIBRARY
                                                   ${_PYTHON_PREFIX}_INCLUDE_DIR)
+    list (APPEND _${_PYTHON_PREFIX}_CACHED_VARS ${_PYTHON_PREFIX}_LIBRARY
+                                                ${_PYTHON_PREFIX}_LIBRARY_RELEASE
+                                                ${_PYTHON_PREFIX}_RUNTIME_LIBRARY_RELEASE
+                                                ${_PYTHON_PREFIX}_LIBRARY_DEBUG
+                                                ${_PYTHON_PREFIX}_RUNTIME_LIBRARY_DEBUG
+                                                ${_PYTHON_PREFIX}_INCLUDE_DIR)
   endif()
 
   # Support preference of static libs by adjusting CMAKE_FIND_LIBRARY_SUFFIXES