build limited api when SOAR_PYTHON_ABI3 is defined

Core/ClientSMLSWIG/Python/Python_sml_ClientInterface.i

@@ -12,7 +12,9 @@
 %include <windows.i>
 
 %begin %{
+#ifdef Soar_Python_ABI3
 #define Py_LIMITED_API 0x03050000
+#endif
 %}
 
 %{

Core/ClientSMLSWIG/Python/SConscript

@@ -59,6 +59,18 @@ install_source = env.Install(lib_install_dir, source)
 install_lib = env.Install(lib_install_dir, shlib)
 install_test = env.Install(lib_install_dir, env.File('TestPythonSML.py'))
 
+if "SOAR_PYTHON_ABI3" in env["ENV"]:
+    if env["SWIG_VERSION"] >= (4, 2, 0):
+        print("SOAR_PYTHON_ABI3 defined, building Python Limited API...")
+        # Signal to SConstruct that we're building the limited API
+        env["PYTHON_LIMITED_API"] = True
+        # Signal to the .i file that we're building the limited API
+        clone.Append(CPPDEFINES = { 'Soar_Python_ABI3': None })
+    else:
+        print("'Requested building Python SML bindings with Python's Limited API, "
+              "while SWIG does not support it, aborting.'", file=sys.stderr)
+        Exit(1)
+
 # We add soarlib to the python_sml explicitly, as some operating systems don't pick up on this dependency,
 # and crash the build.
 Import('soarlib')

Core/ClientSMLSWIG/Python/pyproject.toml

@@ -127,6 +127,7 @@ skip = [
 #
 # We pick python 3.9, since macOS ARM64 doesn't have 3.8, and so this is the earliest version on all platforms.
 build = "cp39*"
+environment = { SOAR_PYTHON_ABI3="1" }
 # This test command:
 #  - imports soar_sml
 #  - creates the kernel

Core/SConscript

@@ -16,21 +16,28 @@ def recursive_glob(treeroot, pattern):
 	return results
 # 	('SoarKernel/SoarKernel.cxx',       recursive_glob(kernel_env.Dir('SoarKernel/src').abspath(), '*.cpp')),    # Kernel
 
-def CheckSWIG(env):
+def SWIGVersion(env):
 	if not env.WhereIs('swig'):
-		return False
-
+		return None
 	p = sub.Popen('swig -version'.split(), stdout=sub.PIPE)
 	out = p.communicate()[0].decode().split()
 	p.wait()
 
-	version = tuple(int(x) for x in out[2].split('.'))
+	return tuple(int(x) for x in out[2].split('.'))
+
+
+def CheckSWIG(env):
+	version = SWIGVersion(env)
+	if version is None:
+		return False
+
 	if version >= (1, 3, 31):
 		return True
 
 	print('swig version 1.3.31 or higher is required')
 	return False
 
+
 kernel_env = env.Clone()
 
 # Windows DLLs need to get linked to dependencies, whereas Linux and Mac shared objects do not
@@ -110,6 +117,7 @@ env.Alias('headers', headers)
 if not CheckSWIG(env):
 	print('SWIG not found. Will not define sml_* build targets. Install swig to build wrappers for other languages.')
 else:
+	env["SWIG_VERSION"] = SWIGVersion(env)
 	for x in 'Python Java Tcl CSharp'.split():
 		SConscript(os.path.join('ClientSMLSWIG', x, 'SConscript'))
 

SConstruct

@@ -421,8 +421,9 @@ if enscons_active:
     # and so we let it determine the wheel tag by itself.
     env['ROOT_IS_PURELIB'] = False
 
-    # This enables tagging the wheel with the limited api, and also sets the target python version.
-    env["LIMITED_API_TARGET"] = (3, 5)
+    if env.get('PYTHON_LIMITED_API', False):
+        # This enables tagging the wheel with the limited api, and also sets the target python version.
+        env["LIMITED_API_TARGET"] = (3, 5)
 
     # Whl and WhlFile add multiple targets (sdist, dist_info, bdist_wheel, editable) to env
     # for enscons (python build backend for scons; required for building with cibuildwheel).