Issue #6551: test_zipimport could import and then destroy some modules of

the encodings package, which would make other tests fail further down
the road because the internally cached encoders and decoders would point
to empty global variables.

4 files changed, 26 insertions, 7 deletions

diff --git a/Lib/test/support.py b/Lib/test/support.py
index 0c69aac6de..7b0241aacc 100644
--- a/Lib/test/support.py
+++ b/Lib/test/support.py
@@ -951,6 +951,23 @@ def run_doctest(module, verbosity=None):
               (module.__name__, t))
     return f, t
 
+
+#=======================================================================
+# Support for saving and restoring the imported modules.
+
+def modules_setup():
+    return sys.modules.copy(),
+
+def modules_cleanup(oldmodules):
+    # Encoders/decoders are registered permanently within the internal
+    # codec cache. If we destroy the corresponding modules their
+    # globals will be set to None which will trip up the cached functions.
+    encodings = [(k, v) for k, v in sys.modules.items()
+                 if k.startswith('encodings.')]
+    sys.modules.clear()
+    sys.modules.update(encodings)
+    sys.modules.update(oldmodules)
+
 #=======================================================================
 # Threading support to prevent reporting refleaks when running regrtest.py -R
 
diff --git a/Lib/test/test_importhooks.py b/Lib/test/test_importhooks.py
index bf2870dbec..1da30b7c77 100644
--- a/Lib/test/test_importhooks.py
+++ b/Lib/test/test_importhooks.py
@@ -143,15 +143,14 @@ class ImportHooksBaseTestCase(unittest.TestCase):
         self.meta_path = sys.meta_path[:]
         self.path_hooks = sys.path_hooks[:]
         sys.path_importer_cache.clear()
-        self.modules_before = sys.modules.copy()
+        self.modules_before = support.modules_setup()
 
     def tearDown(self):
         sys.path[:] = self.path
         sys.meta_path[:] = self.meta_path
         sys.path_hooks[:] = self.path_hooks
         sys.path_importer_cache.clear()
-        sys.modules.clear()
-        sys.modules.update(self.modules_before)
+        support.modules_cleanup(*self.modules_before)
 
 
 class ImportHooksTestCase(ImportHooksBaseTestCase):
diff --git a/Lib/test/test_pkg.py b/Lib/test/test_pkg.py
index 0c568bb3b5..2e293f4fbe 100644
--- a/Lib/test/test_pkg.py
+++ b/Lib/test/test_pkg.py
@@ -48,13 +48,11 @@ class TestPkg(unittest.TestCase):
         self.root = None
         self.pkgname = None
         self.syspath = list(sys.path)
-        self.sysmodules = sys.modules.copy()
+        self.modules_before = support.modules_setup()
 
     def tearDown(self):
         sys.path[:] = self.syspath
-        sys.modules.clear()
-        sys.modules.update(self.sysmodules)
-        del self.sysmodules
+        support.modules_cleanup(*self.modules_before)
         cleanout(self.root)
 
         # delete all modules concerning the tested hiearchy
diff --git a/Misc/NEWS b/Misc/NEWS
index 2d30d504d6..a7b570c461 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -373,6 +373,11 @@ Documentation
 Tests
 -----
 
+- Issue #6551: test_zipimport could import and then destroy some modules of
+  the encodings package, which would make other tests fail further down
+  the road because the internally cached encoders and decoders would point
+  to empty global variables.
+
 - Issue #7295: Do not use a hardcoded file name in test_tarfile.
 
 - Issue #7270: Add some dedicated unit tests for multi-thread synchronization