Add support for PyPy

This skips building the C extension and only uses the pure Python
version when built on PyPy. This is probably the right thing to do on
PyPy anyway, since PyPy needs to use a compatibility layer for the C
extension, and that slows things down considerably.

Running the benchmark suite, the C extension is consistently 10x slower
than the pure Python implementation on PyPy.

setup.py

@@ -1,13 +1,18 @@
 import os
+import platform
 
 import setuptools
 from setuptools import Extension
 
-c_extension = Extension(
-    "backports.zoneinfo._czoneinfo", sources=["lib/zoneinfo_module.c"],
-)
+if platform.python_implementation() != "PyPy":
+    c_extension = Extension(
+        "backports.zoneinfo._czoneinfo", sources=["lib/zoneinfo_module.c"],
+    )
+
+    setuptools.setup(ext_modules=[c_extension])
+else:
+    setuptools.setup()
 
-setuptools.setup(ext_modules=[c_extension])
 
 if "GCNO_TARGET_DIR" in os.environ:
     import glob

tests/_support.py

@@ -1,5 +1,6 @@
 import contextlib
 import functools
+import platform
 import sys
 import threading
 import unittest
@@ -9,6 +10,8 @@
 TZPATH_LOCK = threading.Lock()
 TZPATH_TEST_LOCK = threading.Lock()
 
+IS_PYPY = platform.python_implementation() == "PyPy"
+
 
 def call_once(f):
     """Decorator that ensures a function is only ever called once."""
@@ -33,6 +36,13 @@ def get_modules():
     one time — in other words, when using this function you will only ever
     get one copy of each module rather than a fresh import each time.
     """
+    # PyPy doesn't have a C extension, so for the moment we'll just give it
+    # two copies of the normal module
+    if IS_PYPY:
+        from backports import zoneinfo
+
+        return zoneinfo, zoneinfo
+
     # The standard import_fresh_module approach seems to be somewhat buggy
     # when it comes to C imports, so in the short term, we will do a little
     # module surgery to test this.
@@ -45,7 +55,6 @@ def get_modules():
 
     py_module.ZoneInfo = py_zoneinfo.ZoneInfo
     c_module.ZoneInfo = c_zoneinfo.ZoneInfo
-
     return py_module, c_module
 
 

tests/test_zoneinfo.py

@@ -15,7 +15,7 @@
 from datetime import date, datetime, time, timedelta, timezone
 
 from . import _support as test_support
-from ._support import OS_ENV_LOCK, TZPATH_TEST_LOCK, ZoneInfoTestBase
+from ._support import IS_PYPY, OS_ENV_LOCK, TZPATH_TEST_LOCK, ZoneInfoTestBase
 
 try:
     from functools import cached_property
@@ -36,6 +36,7 @@
 except importlib_metadata.PackageNotFoundError:
     HAS_TZDATA_PKG = False
 
+
 ZONEINFO_DATA = None
 ZONEINFO_DATA_V1 = None
 TEMP_DIR = None
@@ -1771,6 +1772,7 @@ class CTestModule(TestModule):
     module = c_zoneinfo
 
 
+@unittest.skipIf(IS_PYPY, "C Extension not built on PyPy")
 class ExtensionBuiltTest(unittest.TestCase):
     """Smoke test to ensure that the C and Python extensions are both tested.