gh-157146: Make the archive lookup safe during interpreter shutdown

sys.path_importer_cache is set to None early in finalization, before the
objects still referenced from sys attributes are released, so a __del__
can reach linecache while every module it imports is still available.
Return early in that case, and treat an ImportError from the lookup like
the other imports linecache makes lazily.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016oQeaTzLMBouqehAe3W2EU

Author: gpshead

Lib/linecache.py

@@ -158,7 +158,11 @@ def updatecache(filename, module_globals=None):
         if data is None:
             # The file may be inside an archive on the module search path,
             # such as a zip file.
-            data = _read_from_archive(fullname)
+            try:
+                data = _read_from_archive(fullname)
+            except ImportError:
+                # Can happen if the interpreter is shutting down.
+                return []
         if data is not None:
             entry = (
                 len(data),
@@ -215,14 +219,17 @@ def _read_from_archive(filename):
     """
     import os
     import sys
+    importers = sys.path_importer_cache
+    if importers is None:
+        # Cleared while the interpreter is shutting down.
+        return None
     path = filename
     while True:
         parent = os.path.dirname(path)
         if parent == path:
             return None
         path = parent
-        get_data = getattr(sys.path_importer_cache.get(path), 'get_data',
-                           None)
+        get_data = getattr(importers.get(path), 'get_data', None)
         if get_data is None:
             continue
         try:

Lib/test/test_linecache.py

@@ -360,6 +360,23 @@ def test_linecache_python_string(self):
         self.assertEqual(retcode, 0)
         self.assertEqual(stdout, b'')
         self.assertEqual(stderr, b'')
+    def test_lookup_during_interpreter_shutdown(self):
+        # sys.path_importer_cache is set to None early in interpreter
+        # shutdown, before objects still referenced from sys attributes are
+        # released, so a __del__ can end up here while the modules linecache
+        # imports are still available.
+        code = """if 1:
+            import linecache, sys
+            linecache.getlines('/nonexistent/warmup.py')  # import tokenize
+            class Holder:
+                def __del__(self):
+                    lines = linecache.getlines('/nonexistent/x.py')
+                    print('lines:', lines, file=sys.__stderr__)
+            sys.ps1 = Holder()
+            """
+        retcode, stdout, stderr = assert_python_ok('-c', code)
+        self.assertEqual(stderr.strip(), b'lines: []')
+
 
 class LineCacheInvalidationTests(unittest.TestCase):
     def setUp(self):