Avoid .abi3t extension suffixes on Python 3.13t and 3.14t

newsfragments/5363.bugfix.rst

@@ -0,0 +1,4 @@
+Fixed unimportable extensions on free-threaded Python 3.13 and 3.14 when
+``Extension.py_limited_api`` is enabled. These builds now use their
+version-specific extension suffix instead of using the unsupported ``.abi3t``
+suffix.

setuptools/command/build_ext.py

@@ -87,6 +87,10 @@ def get_abi3_suffix():
     if get_config_var('DYNLOADFILE') == 'dynload_hpux.o':
         return None
 
+    # The 3.13t and 3.14t loaders cannot import .abi3t files.
+    if suffix.startswith(('.cpython-313t', '.cpython-314t')):
+        return None
+
     abi = '.abi3t' if get_config_var('Py_GIL_DISABLED') else '.abi3'
     platform = get_config_var('SOABI_PLATFORM')
     _, ext = os.path.splitext(suffix)

setuptools/tests/test_bdist_wheel.py

@@ -7,6 +7,7 @@
 import shutil
 import stat
 import struct
+import subprocess
 import sys
 import sysconfig
 from contextlib import nullcontext, suppress
@@ -18,6 +19,7 @@
 from packaging import tags
 
 import setuptools
+from setuptools.archive_util import unpack_zipfile
 from setuptools.command.bdist_wheel import bdist_wheel, get_abi_tag, stable_abi_tag
 from setuptools.command.build_ext import get_abi3_suffix
 from setuptools.dist import Distribution
@@ -529,17 +531,24 @@ def test_limited_api(monkeypatch, tmp_path, tmp_path_factory):
 @pytest.mark.filterwarnings(
     "once:Config variable '.*' is unset.*, Python ABI tag may be incorrect"
 )
-def test_version_specific_abi(monkeypatch, tmp_path, tmp_path_factory):
-    """Extensions not using the limited API get a version-specific ABI tag."""
+@pytest.mark.parametrize('limited_api', [False, True])
+def test_version_specific_abi(monkeypatch, tmp_path, tmp_path_factory, limited_api):
+    """Version-specific wheels must import with or without py_limited_api."""
     source_dir = tmp_path_factory.mktemp("extension_dist")
-    (source_dir / "setup.py").write_text(VERSION_SPECIFIC_SETUPPY, encoding="utf-8")
+    setup_py = EXTENSION_SETUPPY if limited_api else VERSION_SPECIFIC_SETUPPY
+    (source_dir / "setup.py").write_text(setup_py, encoding="utf-8")
     (source_dir / "extension.c").write_text(EXTENSION_BODY, encoding="utf-8")
     build_dir = tmp_path.joinpath("build")
     dist_dir = tmp_path.joinpath("dist")
     monkeypatch.chdir(source_dir)
     bdist_wheel_cmd(bdist_dir=str(build_dir), dist_dir=str(dist_dir)).run()
     wheel_path = next(dist_dir.glob("*.whl"))
     assert f"-{get_abi_tag()}-" in wheel_path.name
+    installed = tmp_path / 'installed'
+    unpack_zipfile(wheel_path, installed)
+    subprocess.run(
+        [sys.executable, '-c', 'import extension'], cwd=installed, check=True
+    )
 
 
 @pytest.mark.skipif(

setuptools/tests/test_build_ext.py

@@ -53,6 +53,8 @@
         ({'Py_GIL_DISABLED': 1, 'VERSION': None}, '.abi3t.so'),
         ({'Py_GIL_DISABLED': 1, 'VERSION': '3.14'}, '.abi3t.so'),
         ({'Py_GIL_DISABLED': 1, 'VERSION': '3.13'}, '.abi3t.so'),
+        ({'EXT_SUFFIX': '.cpython-313t-darwin.so', 'Py_GIL_DISABLED': 1}, None),
+        ({'EXT_SUFFIX': '.cpython-314t-darwin.so', 'Py_GIL_DISABLED': 1}, None),
         ({'EXT_SUFFIX': '.cp315-win_amd64.pyd'}, '.pyd'),
         ({'EXT_SUFFIX': '.cp315-win_arm64.pyd'}, '.pyd'),
         ({'EXT_SUFFIX': '.cp310-win32.pyd'}, '.pyd'),
@@ -169,11 +171,10 @@ def test_ext_suffix_override(self):
         # Mock value needed to pass tests
         ext._links_to_dynamic = False
 
-        if not IS_PYPY:
+        if not IS_PYPY and get_abi3_suffix():
             expect = cmd.get_ext_filename('for_abi3')
         else:
-            # PyPy builds do not use ABI3 tag, so they will
-            # also get the overridden suffix.
+            # Builds without an ABI3 tag also get the overridden suffix.
             expect = 'for_abi3.test-suffix'
 
         try: