Merge pull request #4754 from mwichmann/test/runtest-py

Minor test-releated tweak for Python selection

Author: bdbaddog

CHANGES.txt

@@ -162,6 +162,8 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
     - Improve the wording of Configure methods.
     - Add unit test cases for AppendUnique, PrependUnique - verify behavior
       if existing value already contained more than one of added value.
+    - Tweak runtest.py and test framework to more reliably get the requested
+      Python binary (for odd Windows setups + Python launcher)
 
 
 RELEASE 4.9.1 -  Thu, 27 Mar 2025 11:40:20 -0700

RELEASE.txt

@@ -83,6 +83,9 @@ FIXES
   as the default path for temporary files includes the username. Setting
   (existing) TEMPFILEDIR may also help in this case.
 
+- Tweak runtest.py and test framework to more reliably get the requested
+  Python binary (for odd Windows setups + Python launcher)
+
 IMPROVEMENTS
 ------------
 

runtest.py

@@ -1,7 +1,9 @@
-#!/usr/bin/env python
+#!/usr/bin/python
 #
-# Copyright The SCons Foundation
+# SPDX-License-Identifier: MIT
 #
+# Copyright The SCons Foundation
+
 """runtest - wrapper script for running SCons tests
 
 The SCons test suite consists of:

testing/framework/TestSCons.py

@@ -1724,15 +1724,23 @@ def get_platform_python_info(self, python_h_required: bool = False):
 
         Returns a path to a Python executable suitable for testing on
         this platform and its associated include path, library path and
-        library name.
+        library name. ``runtest.py`` sets an environment variable with the
+        desired Python path, so if we're started from there, use that.
+
+        This exists because of SWIG, which may need to build things against
+        the Python header and library.  The approach is a bit of a large
+        hammer: we run a script like we would a test, and capture the results,
+        rather than querying the running Python. This supports the test
+        runner's ``-P`` option to specify an alternate Python, otherwise
+        we wouldn't need to be this complex.
 
         If the Python executable or Python header (if required)
         is not found, the test is skipped.
 
         Returns:
             tuple: path to python, include path, library path, library name
         """
-        python = os.environ.get('python_executable', self.where_is('python'))
+        python = os.environ.get('python_executable', sys.executable)
         if not python:
             self.skip_test(
                 'Can not find installed "python", skipping test.\n', from_fw=True