From d6184e5cff4d3bf3a210e398e1c2ac20c9e526e1 Mon Sep 17 00:00:00 2001
From: Adriaan de Groot <groot@kde.org>
Date: Mon, 22 Jul 2024 23:11:49 +0200
Subject: [PATCH] CMake: make finding-python-version a little more flexible

My development machine has Python 3.11 installed, with all the
development tools, and 3.12 with only the interpreter. I can't
get find_package(Python3) to find 3.11 unless specifying EXACT,
since it always ends up preferring 3.12 which doesn't have the
required components.
---
 CMakeLists.txt | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5f055352a..5825a8e53 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -37,6 +37,7 @@
 #                       - SCHEMA_TESTING (requires Python, see ci/configvalidator.py)
 #                       - TESTING (standard CMake option)
 #   DEBUG_<foo>     : special developer flags for debugging.
+#   PYTHONLIBS_VERSION : if set on the command-line, use a specific Python version
 #
 # Example usage:
 #
@@ -101,6 +102,14 @@ option(BUILD_CRASH_REPORTING "Enable crash reporting with KCrash." ON)
 #  - DEBUG_PARTITION_UNSAFE (see partition/CMakeLists.txt)
 #  - DEBUG_PARTITION_BAIL_OUT (see partition/CMakeLists.txt)
 
+# Special handling for Python versions:
+#  - If you set PYTHONLIBS_VERSION on the command-line, then
+#    that **exact** version will be searched for, and no other.
+#  - If you do not set PYTHONLIBS_VERSION on the command-line,
+#    any suitable version will be found -- but this can fail if
+#    you have multiple Python versions installed, only some of
+#    which include the development headers.
+
 ### USE_*
 #
 # By convention, when there are multiple modules that implement similar
@@ -208,7 +217,12 @@ else()
 endif()
 
 set(BOOSTPYTHON_VERSION 1.72.0)
-set(PYTHONLIBS_VERSION 3.6)
+if(DEFINED PYTHONLIBS_VERSION)
+    set(PYTHONLIBS_EXTRA "EXACT")
+else()
+    set(PYTHONLIBS_VERSION 3.6)
+    set(PYTHONLIBS_EXTRA "")
+endif()
 set(YAMLCPP_VERSION 0.5.1)
 
 ### CMAKE SETUP
@@ -412,7 +426,7 @@ if(NOT TARGET ${kfname}::Crash)
     set(BUILD_CRASH_REPORTING OFF)
 endif()
 
-find_package(Python ${PYTHONLIBS_VERSION} COMPONENTS Interpreter Development)
+find_package(Python ${PYTHONLIBS_VERSION} ${PYTHONLIBS_EXTRA} COMPONENTS Interpreter Development)
 set_package_properties(
     Python
     PROPERTIES