From bbb927a85ec6e132b76f1dea86763bfd8e2f4ca7 Mon Sep 17 00:00:00 2001
From: "Jason R. Coombs" <jaraco@jaraco.com>
Date: Wed, 6 Mar 2024 10:58:25 -0500
Subject: [PATCH] gh-116307: Create a new import helper 'isolated modules' and
 use that instead of 'Clean Import' to ensure that tests from
 importlib_resources don't leave modules in sys.modules.

---
 Lib/test/support/import_helper.py                    | 12 ++++++++++++
 Lib/test/test_importlib/resources/test_files.py      |  2 +-
 .../2024-03-06-11-00-36.gh-issue-116307.Uij0t_.rst   |  3 +++
 3 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Tests/2024-03-06-11-00-36.gh-issue-116307.Uij0t_.rst

diff --git a/Lib/test/support/import_helper.py b/Lib/test/support/import_helper.py
index 3d804f2b590108..29c6f535b40342 100644
--- a/Lib/test/support/import_helper.py
+++ b/Lib/test/support/import_helper.py
@@ -268,6 +268,18 @@ def modules_cleanup(oldmodules):
     sys.modules.update(oldmodules)
 
 
+@contextlib.contextmanager
+def isolated_modules():
+    """
+    Save modules on entry and cleanup on exit.
+    """
+    (saved,) = modules_setup()
+    try:
+        yield
+    finally:
+        modules_cleanup(saved)
+
+
 def mock_register_at_fork(func):
     # bpo-30599: Mock os.register_at_fork() when importing the random module,
     # since this function doesn't allow to unregister callbacks and would leak
diff --git a/Lib/test/test_importlib/resources/test_files.py b/Lib/test/test_importlib/resources/test_files.py
index 1450cfb310926a..26c8b04e44c3b9 100644
--- a/Lib/test/test_importlib/resources/test_files.py
+++ b/Lib/test/test_importlib/resources/test_files.py
@@ -70,7 +70,7 @@ def setUp(self):
         self.addCleanup(self.fixtures.close)
         self.site_dir = self.fixtures.enter_context(os_helper.temp_dir())
         self.fixtures.enter_context(import_helper.DirsOnSysPath(self.site_dir))
-        self.fixtures.enter_context(import_helper.CleanImport())
+        self.fixtures.enter_context(import_helper.isolated_modules())
 
 
 class ModulesFilesTests(SiteDir, unittest.TestCase):
diff --git a/Misc/NEWS.d/next/Tests/2024-03-06-11-00-36.gh-issue-116307.Uij0t_.rst b/Misc/NEWS.d/next/Tests/2024-03-06-11-00-36.gh-issue-116307.Uij0t_.rst
new file mode 100644
index 00000000000000..0bc4be94789f21
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2024-03-06-11-00-36.gh-issue-116307.Uij0t_.rst
@@ -0,0 +1,3 @@
+Added import helper ``isolated_modules`` as ``CleanImport`` does not remove
+modules imported during the context. Use it in importlib.resources tests to
+avoid leaving ``mod`` around to impede importlib.metadata tests.