RustPython · youknowone · Jun 2, 2026 · Jun 2, 2026 · Jun 2, 2026
diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py
@@ -1375,6 +1375,14 @@ def _find_and_load(name, import_):
         # NOTE: because of this, initializing must be set *before*
         # putting the new module in sys.modules.
         _lock_unlock_module(name)
+    else:
+        # Verify the module is still in sys.modules. Another thread may have
+        # removed it (due to import failure) between our sys.modules.get()
+        # above and the _initializing check. If removed, we retry the import
+        # to preserve normal semantics: the caller gets the exception from
+        # the actual import failure rather than a synthetic error.
+        if sys.modules.get(name) is not module:
+            return _find_and_load(name, import_)
 
     if module is None:
         message = f'import of {name} halted; None in sys.modules'

diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
@@ -946,7 +946,7 @@ def get_filename(self, fullname):
 
     def get_data(self, path):
         """Return the data from path as raw bytes."""
-        if isinstance(self, (SourceLoader, ExtensionFileLoader)):
+        if isinstance(self, (SourceLoader, SourcelessFileLoader, ExtensionFileLoader)):
             with _io.open_code(str(path)) as file:
                 return file.read()
         else:

diff --git a/Lib/test/test_importlib/frozen/test_loader.py b/Lib/test/test_importlib/frozen/test_loader.py
@@ -5,7 +5,6 @@
 from test.support import captured_stdout, import_helper, STDLIB_DIR
 import contextlib
 import os.path
-import sys
 import types
 import unittest
 import warnings
@@ -76,7 +75,7 @@ def test_module(self):
         self.assertHasAttr(module, '__spec__')
         self.assertEqual(module.__spec__.loader_state.origname, name)
 
-    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON")
+    @unittest.skipIf(__import__("sys").platform == "win32", "TODO: RUSTPYTHON")
     def test_package(self):
         name = '__phello__'
         module, output = self.exec_module(name)
@@ -147,7 +146,7 @@ def test_get_source(self):
             result = self.machinery.FrozenImporter.get_source('__hello__')
         self.assertIsNone(result)
 
-    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON")
+    @unittest.skipIf(__import__("sys").platform == "win32", "TODO: RUSTPYTHON")
     def test_is_package(self):
         # Should be able to tell what is a package.
         test_for = (('__hello__', False), ('__phello__', True),

diff --git a/Lib/test/test_importlib/resources/test_resource.py b/Lib/test/test_importlib/resources/test_resource.py
@@ -1,4 +1,3 @@
-import os
 import unittest
 
 from . import util

diff --git a/Lib/test/test_importlib/test_locks.py b/Lib/test/test_importlib/test_locks.py
@@ -155,8 +155,8 @@ def test_all_locks(self):
 
 # TODO: RUSTPYTHON; dead weakref module locks not cleaned up in frozen bootstrap
 Frozen_LifetimeTests.test_all_locks = unittest.skip("TODO: RUSTPYTHON")(
-    Frozen_LifetimeTests.test_all_locks)
-
+    Frozen_LifetimeTests.test_all_locks
+)
 
 def setUpModule():
     thread_info = threading_helper.threading_setup()

diff --git a/Lib/test/test_importlib/test_threaded_import.py b/Lib/test/test_importlib/test_threaded_import.py
@@ -263,6 +263,72 @@ def test_multiprocessing_pool_circular_import(self, size):
                           'partial', 'pool_in_threads.py')
         script_helper.assert_python_ok(fn)
 
+    @unittest.expectedFailure  # TODO: RUSTPYTHON
+    def test_import_failure_race_condition(self):
+        # Regression test for race condition where a thread could receive
+        # a partially-initialized module when another thread's import fails.
+        # The race occurs when:
+        # 1. Thread 1 starts importing, adds module to sys.modules
+        # 2. Thread 2 sees the module in sys.modules
+        # 3. Thread 1's import fails, removes module from sys.modules
+        # 4. Thread 2 should NOT return the stale module reference
+        os.mkdir(TESTFN)
+        self.addCleanup(shutil.rmtree, TESTFN)
+        sys.path.insert(0, TESTFN)
+        self.addCleanup(sys.path.remove, TESTFN)
+
+        # Create a module that partially initializes then fails
+        modname = 'failing_import_module'
+        with open(os.path.join(TESTFN, modname + '.py'), 'w') as f:
+            f.write('''
+import time
+PARTIAL_ATTR = 'initialized'
+time.sleep(0.05)  # Widen race window
+raise RuntimeError("Intentional import failure")
+''')
+        self.addCleanup(forget, modname)
+        importlib.invalidate_caches()
+
+        errors = []
+        results = []
+
+        def do_import(delay=0):
+            time.sleep(delay)
+            try:
+                mod = __import__(modname)
+                # If we got a module, verify it's in sys.modules
+                if modname not in sys.modules:
+                    errors.append(
+                        f"Got module {mod!r} but {modname!r} not in sys.modules"
+                    )
+                elif sys.modules[modname] is not mod:
+                    errors.append(
+                        f"Got different module than sys.modules[{modname!r}]"
+                    )
+                else:
+                    results.append(('success', mod))
+            except RuntimeError:
+                results.append(('RuntimeError',))
+            except Exception as e:
+                errors.append(f"Unexpected exception: {e}")
+
+        # Run multiple iterations to increase chance of hitting the race
+        for _ in range(10):
+            errors.clear()
+            results.clear()
+            if modname in sys.modules:
+                del sys.modules[modname]
+
+            t1 = threading.Thread(target=do_import, args=(0,))
+            t2 = threading.Thread(target=do_import, args=(0.01,))
+            t1.start()
+            t2.start()
+            t1.join()
+            t2.join()
+
+            # Neither thread should have errors about stale modules
+            self.assertEqual(errors, [], f"Race condition detected: {errors}")
+
 
 def setUpModule():
     thread_info = threading_helper.threading_setup()

diff --git a/Lib/test/test_importlib/util.py b/Lib/test/test_importlib/util.py
@@ -15,10 +15,10 @@
 import tempfile
 import types
 
-try:
-    _testsinglephase = import_helper.import_module("_testsinglephase")
+try: # TODO: RUSTPYTHON
+    import_helper.import_module("_testmultiphase")
 except unittest.SkipTest:
-    _testsinglephase = None  # TODO: RUSTPYTHON
+    _testmultiphase = None
 
 
 BUILTINS = types.SimpleNamespace()