[3.10] bpo-45183: don't raise an exception when calling zipimport.zipimporter.find_spec() when the zip file is missing and the internal cache has been reset (GH-28435) (#28438)

This can occur when the zip file gets deleted, you call zipimport.zipimporter.invalidate_cache(), and then try to use zipimport.zipimporter.find_spec() (i.e. you left the zip file path on sys.path).
(cherry picked from commit 209b7035f7)

Co-authored-by: Brett Cannon <brett@python.org>

Lib/test/test_zipimport.py

@@ -547,8 +547,9 @@ def testInvalidateCaches(self):
         # Check that the cached data is removed if the file is deleted
         os.remove(TEMP_ZIP)
         zi.invalidate_caches()
-        self.assertIsNone(zi._files)
+        self.assertFalse(zi._files)
         self.assertIsNone(zipimport._zip_directory_cache.get(zi.archive))
+        self.assertIsNone(zi.find_spec("name_does_not_matter"))
 
     def testZipImporterMethodsInSubDirectory(self):
         packdir = TESTPACK + os.sep

Lib/zipimport.py

@@ -334,7 +334,7 @@ def invalidate_caches(self):
             _zip_directory_cache[self.archive] = self._files
         except ZipImportError:
             _zip_directory_cache.pop(self.archive, None)
-            self._files = None
+            self._files = {}
 
 
     def __repr__(self):

Misc/NEWS.d/next/Library/2021-09-17-15-58-53.bpo-45183.Vv_vch.rst

@@ -0,0 +1,3 @@
+Have zipimport.zipimporter.find_spec() not raise an exception when the underlying zip
+file has been deleted and the internal cache has been reset via
+invalidate_cache().

Python/importlib_zipimport.h

@@ -548,7 +548,7 @@ const unsigned char _Py_M__zipimport[] = {
     0,106,1,131,1,124,0,95,2,124,0,106,2,116,3,124,
     0,106,1,60,0,87,0,100,1,83,0,4,0,116,4,121,
     35,1,0,1,0,1,0,116,3,160,5,124,0,106,1,100,
-    1,161,2,1,0,100,1,124,0,95,2,89,0,100,1,83,
+    1,161,2,1,0,105,0,124,0,95,2,89,0,100,1,83,
     0,119,0,41,2,122,41,82,101,108,111,97,100,32,116,104,
     101,32,102,105,108,101,32,100,97,116,97,32,111,102,32,116,
     104,101,32,97,114,99,104,105,118,101,32,112,97,116,104,46,