Fix the test for read-only tempdir. Reduce the number of attempts even more.

Author: serhiy-storchaka

Lib/tempfile.py

@@ -57,7 +57,10 @@
 if hasattr(_os, 'O_BINARY'):
     _bin_openflags |= _os.O_BINARY
 
-TMP_MAX = 100
+if hasattr(_os, 'TMP_MAX'):
+    TMP_MAX = _os.TMP_MAX
+else:
+    TMP_MAX = 10000
 
 # This variable _was_ unused for legacy reasons, see issue 10354.
 # But as of 3.5 we actually use it at runtime so changing it would
@@ -210,14 +213,10 @@ def _get_default_tempdir(dirlist=None):
             except FileExistsError:
                 pass
             except PermissionError:
-                # On Posix, this exception is raised when the user has no
-                # write access to the parent directory.
-                # On Windows, it is also raised when a directory with
-                # the chosen name already exists, or if the parent directory
-                # is not a directory.
-                # We cannot distinguish between "directory-exists-error" and
-                # "access-denied-error".
-                if _os.name == 'nt' and _os.path.isdir(dir):
+                # This exception is thrown when a directory with the chosen name
+                # already exists on windows.
+                if (_os.name == 'nt' and _os.path.isdir(dir) and
+                    _os.access(dir, _os.W_OK)):
                     continue
                 break   # no point trying more names in this directory
             except OSError:
@@ -259,14 +258,10 @@ def _mkstemp_inner(dir, pre, suf, flags, output_type):
         except FileExistsError:
             continue    # try again
         except PermissionError:
-            # On Posix, this exception is raised when the user has no
-            # write access to the parent directory.
-            # On Windows, it is also raised when a directory with
-            # the chosen name already exists, or if the parent directory
-            # is not a directory.
-            # We cannot distinguish between "directory-exists-error" and
-            # "access-denied-error".
-            if _os.name == 'nt' and _os.path.isdir(dir) and seq < TMP_MAX - 1:
+            # This exception is thrown when a directory with the chosen name
+            # already exists on windows.
+            if (_os.name == 'nt' and _os.path.isdir(dir) and
+                _os.access(dir, _os.W_OK)):
                 continue
             else:
                 raise
@@ -391,14 +386,10 @@ def mkdtemp(suffix=None, prefix=None, dir=None):
         except FileExistsError:
             continue    # try again
         except PermissionError:
-            # On Posix, this exception is raised when the user has no
-            # write access to the parent directory.
-            # On Windows, it is also raised when a directory with
-            # the chosen name already exists, or if the parent directory
-            # is not a directory.
-            # We cannot distinguish between "directory-exists-error" and
-            # "access-denied-error".
-            if _os.name == 'nt' and _os.path.isdir(dir) and seq < TMP_MAX - 1:
+            # This exception is thrown when a directory with the chosen name
+            # already exists on windows.
+            if (_os.name == 'nt' and _os.path.isdir(dir) and
+                _os.access(dir, _os.W_OK)):
                 continue
             else:
                 raise

Lib/test/test_tempfile.py

@@ -330,17 +330,36 @@ def _mock_candidate_names(*names):
 class TestBadTempdir:
     def test_read_only_directory(self):
         with _inside_empty_temp_dir():
-            oldmode = mode = os.stat(tempfile.tempdir).st_mode
-            mode &= ~(stat.S_IWUSR | stat.S_IWGRP | stat.S_IWOTH)
-            os.chmod(tempfile.tempdir, mode)
+            probe = os.path.join(tempfile.tempdir, 'probe')
+            if os.name == 'nt':
+                cmd = ['icacls', tempfile.tempdir, '/deny', 'Everyone:(W)']
+                stdout = None if support.verbose > 1 else subprocess.DEVNULL
+                subprocess.run(cmd, check=True, stdout=stdout)
+            else:
+                oldmode = mode = os.stat(tempfile.tempdir).st_mode
+                mode &= ~(stat.S_IWUSR | stat.S_IWGRP | stat.S_IWOTH)
+                mode = stat.S_IREAD
+                os.chmod(tempfile.tempdir, mode)
             try:
-                if os.access(tempfile.tempdir, os.W_OK):
+                # Check that the directory is read-only.
+                try:
+                    os.mkdir(probe)
+                except PermissionError:
+                    pass
+                else:
+                    os.rmdir(probe)
                     self.skipTest("can't set the directory read-only")
+                # gh-66305: Now it takes a split second, but previously
+                # it took about 10 days on Windows.
                 with self.assertRaises(PermissionError):
                     self.make_temp()
-                self.assertEqual(os.listdir(tempfile.tempdir), [])
             finally:
-                os.chmod(tempfile.tempdir, oldmode)
+                if os.name == 'nt':
+                    cmd = ['icacls', tempfile.tempdir, '/grant:r', 'Everyone:(M)']
+                    subprocess.run(cmd, check=True, stdout=stdout)
+                else:
+                    os.chmod(tempfile.tempdir, oldmode)
+            self.assertEqual(os.listdir(tempfile.tempdir), [])
 
     def test_nonexisting_directory(self):
         with _inside_empty_temp_dir():