bpo-40280: Detect missing threading on WASM platforms (GH-32352)

Co-authored-by: Brett Cannon <[email protected]>

Author: tiran

Lib/distutils/tests/test_build_ext.py

@@ -17,6 +17,7 @@
 from test import support
 from test.support import os_helper
 from test.support.script_helper import assert_python_ok
+from test.support import threading_helper
 
 # http://bugs.python.org/issue4373
 # Don't load the xx module more than once.
@@ -165,6 +166,7 @@ def test_user_site(self):
         self.assertIn(lib, cmd.rpath)
         self.assertIn(incl, cmd.include_dirs)
 
+    @threading_helper.requires_working_threading()
     def test_optional_extension(self):
 
         # this extension will fail, but let's ignore this failure

Lib/test/libregrtest/main.py

@@ -20,6 +20,7 @@
 from test.libregrtest.utils import removepy, count, format_duration, printlist
 from test import support
 from test.support import os_helper
+from test.support import threading_helper
 
 
 # bpo-38203: Maximum delay in seconds to exit Python (call Py_Finalize()).
@@ -676,7 +677,8 @@ def main(self, tests=None, **kwargs):
         except SystemExit as exc:
             # bpo-38203: Python can hang at exit in Py_Finalize(), especially
             # on threading._shutdown() call: put a timeout
-            faulthandler.dump_traceback_later(EXIT_TIMEOUT, exit=True)
+            if threading_helper.can_start_thread:
+                faulthandler.dump_traceback_later(EXIT_TIMEOUT, exit=True)
 
             sys.exit(exc.code)
 

Lib/test/pickletester.py

@@ -1380,6 +1380,7 @@ def test_truncated_data(self):
             self.check_unpickling_error(self.truncated_errors, p)
 
     @threading_helper.reap_threads
+    @threading_helper.requires_working_threading()
     def test_unpickle_module_race(self):
         # https://bugs.python.org/issue34572
         locker_module = dedent("""

Lib/test/support/threading_helper.py

@@ -4,6 +4,7 @@
 import sys
 import threading
 import time
+import unittest
 
 from test import support
 
@@ -210,7 +211,7 @@ def __exit__(self, *exc_info):
 
 
 def _can_start_thread() -> bool:
-    """Detect if Python can start new threads.
+    """Detect whether Python can start new threads.
 
     Some WebAssembly platforms do not provide a working pthread
     implementation. Thread support is stubbed and any attempt
@@ -234,3 +235,15 @@ def _can_start_thread() -> bool:
         return True
 
 can_start_thread = _can_start_thread()
+
+def requires_working_threading(*, module=False):
+    """Skip tests or modules that require working threading.
+
+    Can be used as a function/class decorator or to skip an entire module.
+    """
+    msg = "requires threading support"
+    if module:
+        if not can_start_thread:
+            raise unittest.SkipTest(msg)
+    else:
+        return unittest.skipUnless(can_start_thread, msg)

Lib/test/test_bz2.py

@@ -496,6 +496,7 @@ def testContextProtocol(self):
         else:
             self.fail("1/0 didn't raise an exception")
 
+    @threading_helper.requires_working_threading()
     def testThreading(self):
         # Issue #7205: Using a BZ2File from several threads shouldn't deadlock.
         data = b"1" * 2**20

Lib/test/test_capi.py

@@ -710,6 +710,7 @@ def pendingcalls_wait(self, l, n, context = None):
         if False and support.verbose:
             print("(%i)"%(len(l),))
 
+    @threading_helper.requires_working_threading()
     def test_pendingcalls_threaded(self):
 
         #do every callback on a separate thread
@@ -840,6 +841,7 @@ def test_module_state_shared_in_global(self):
 class TestThreadState(unittest.TestCase):
 
     @threading_helper.reap_threads
+    @threading_helper.requires_working_threading()
     def test_thread_state(self):
         # some extra thread-state tests driven via _testcapi
         def target():

Lib/test/test_context.py

@@ -6,6 +6,7 @@
 import time
 import unittest
 import weakref
+from test.support import threading_helper
 
 try:
     from _testcapi import hamt
@@ -341,6 +342,7 @@ def ctx2_fun():
         ctx1.run(ctx1_fun)
 
     @isolated_context
+    @threading_helper.requires_working_threading()
     def test_context_threads_1(self):
         cvar = contextvars.ContextVar('cvar')
 

Lib/test/test_decimal.py

@@ -39,6 +39,7 @@
                           run_with_locale, cpython_only,
                           darwin_malloc_err_warning)
 from test.support.import_helper import import_fresh_module
+from test.support import threading_helper
 from test.support import warnings_helper
 import random
 import inspect
@@ -1591,6 +1592,8 @@ def thfunc2(cls):
     for sig in Overflow, Underflow, DivisionByZero, InvalidOperation:
         cls.assertFalse(thiscontext.flags[sig])
 
+
+@threading_helper.requires_working_threading()
 class ThreadingTest(unittest.TestCase):
     '''Unit tests for thread local contexts in Decimal.'''
 

Lib/test/test_email/test_email.py

@@ -3285,6 +3285,7 @@ def test_getaddresses_header_obj(self):
         addrs = utils.getaddresses([Header('Al Person <[email protected]>')])
         self.assertEqual(addrs[0][1], '[email protected]')
 
+    @threading_helper.requires_working_threading()
     def test_make_msgid_collisions(self):
         # Test make_msgid uniqueness, even with multiple threads
         class MsgidsThread(Thread):

Lib/test/test_enum.py

@@ -2949,6 +2949,7 @@ class Color(StrMixin, AllMixin, Flag):
         self.assertEqual(str(Color.BLUE), 'blue')
 
     @threading_helper.reap_threads
+    @threading_helper.requires_working_threading()
     def test_unique_composite(self):
         # override __eq__ to be identity only
         class TestFlag(Flag):
@@ -3481,6 +3482,7 @@ class Color(StrMixin, AllMixin, IntFlag):
         self.assertEqual(str(Color.BLUE), 'blue')
 
     @threading_helper.reap_threads
+    @threading_helper.requires_working_threading()
     def test_unique_composite(self):
         # override __eq__ to be identity only
         class TestFlag(IntFlag):