Revert "DRTVWR-587: Simplify Python.cmake by omitting find_package(Python3)."

1 files changed, 39 insertions, 8 deletions

diff --git a/indra/cmake/Python.cmake b/indra/cmake/Python.cmake
index 316f49ba59..2167fb7864 100644
--- a/indra/cmake/Python.cmake
+++ b/indra/cmake/Python.cmake
@@ -7,20 +7,51 @@ if (DEFINED ENV{PYTHON})
   set(python "$ENV{PYTHON}")
   set(PYTHONINTERP_FOUND ON)
 elseif (WINDOWS)
-  if (DEFINED ENV{VIRTUAL_ENV})
-    set(Python3_FIND_VIRTUALENV "ONLY")
-  endif()
+  # On Windows, explicitly avoid Cygwin Python.
+
+  # if the user has their own version of Python installed, prefer that
+  foreach(hive HKEY_CURRENT_USER HKEY_LOCAL_MACHINE)
+    # prefer more recent Python versions to older ones, if multiple versions
+    # are installed
+    foreach(pyver 3.11 3.10 3.9 3.8 3.7)
+      list(APPEND regpaths "[${hive}\\SOFTWARE\\Python\\PythonCore\\${pyver}\\InstallPath]")
+    endforeach()
+  endforeach()
+
+  # TODO: This logic has the disadvantage that if you have multiple versions
+  # of Python installed, the selected path won't necessarily be the newest -
+  # e.g. this GLOB will prefer Python310 to Python311. But since pymaybe is
+  # checked AFTER the registry entries, this will only surface as a problem if
+  # no installed Python appears in the registry.
+  file(GLOB pymaybe
+    "$ENV{PROGRAMFILES}/Python*"
+##  "$ENV{PROGRAMFILES(X86)}/Python*"
+    # The Windows environment variable is in fact as shown above, but CMake
+    # disallows querying an environment variable containing parentheses -
+    # thanks, Windows. Fudge by just appending " (x86)" to $PROGRAMFILES and
+    # hoping for the best.
+    "$ENV{PROGRAMFILES} (x86)/Python*"
+    "c:/Python*")
+
+  find_program(python
+    NAMES python3.exe python.exe
+    NO_DEFAULT_PATH # added so that cmake does not find cygwin python
+    PATHS
+    ${regpaths}
+    ${pymaybe}
+    )
   find_package(Python3 COMPONENTS Interpreter)
-  set(python ${Python3_EXECUTABLE})
 else()
   find_program(python python3)
+
+  if (python)
+    set(PYTHONINTERP_FOUND ON)
+  endif (python)
 endif (DEFINED ENV{PYTHON})
 
-if (python)
-  set(PYTHONINTERP_FOUND ON)
-else()
+if (NOT python)
   message(FATAL_ERROR "No Python interpreter found")
-endif (python)
+endif (NOT python)
 
 set(PYTHON_EXECUTABLE "${python}" CACHE FILEPATH "Python interpreter for builds")
 mark_as_advanced(PYTHON_EXECUTABLE)