From: =?utf-8?q?Timo_R=C3=B6hling?= <roehling@debian.org>
Date: Mon, 13 Sep 2021 18:59:25 +0200
Subject: Prefer Debian default version of Python

---
 Modules/FindPython/Support.cmake | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Modules/FindPython/Support.cmake b/Modules/FindPython/Support.cmake
index 8e70e11..828e075 100644
--- a/Modules/FindPython/Support.cmake
+++ b/Modules/FindPython/Support.cmake
@@ -23,6 +23,20 @@ if (NOT DEFINED _${_PYTHON_PREFIX}_REQUIRED_VERSION_MAJOR)
 endif()
 if (_${_PYTHON_PREFIX}_REQUIRED_VERSION_MAJOR EQUAL "3")
   set(_${_PYTHON_PREFIX}_VERSIONS 3.10 3.9 3.8 3.7 3.6 3.5 3.4 3.3 3.2 3.1 3.0)
+  # Debian-specific: prefer current default version
+  execute_process(
+    COMMAND py3versions -vd
+    OUTPUT_VARIABLE _${_PYTHON_PREFIX}_DEFAULT_VERSION
+    RESULT_VARIABLE _${_PYTHON_PREFIX}_DEFAULT_RESULT
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+    ERROR_QUIET
+  )
+  if(NOT _${_PYTHON_PREFIX}_DEFAULT_RESULT)
+    list(REMOVE_ITEM _${_PYTHON_PREFIX}_VERSIONS ${_${_PYTHON_PREFIX}_DEFAULT_VERSION})
+    list(INSERT _${_PYTHON_PREFIX}_VERSIONS 0 ${_${_PYTHON_PREFIX}_DEFAULT_VERSION})
+  endif()
+  unset(_${_PYTHON_PREFIX}_DEFAULT_RESULT)
+  unset(_${_PYTHON_PREFIX}_DEFAULT_VERSION)
 elseif (_${_PYTHON_PREFIX}_REQUIRED_VERSION_MAJOR EQUAL "2")
   set(_${_PYTHON_PREFIX}_VERSIONS 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0)
 else()