Issue #16800: tempfile.gettempdir() no longer left temporary files when

the disk is full.  Original patch by Amir Szekely.

Lib/tempfile.py

@@ -175,11 +175,14 @@ def _get_default_tempdir():
             filename = _os.path.join(dir, name)
             try:
                 fd = _os.open(filename, _bin_openflags, 0o600)
-                fp = _io.open(fd, 'wb')
-                fp.write(b'blat')
-                fp.close()
-                _os.unlink(filename)
-                del fp, fd
+                try:
+                    try:
+                        fp = _io.open(fd, 'wb', buffering=0, closefd=False)
+                        fp.write(b'blat')
+                    finally:
+                        _os.close(fd)
+                finally:
+                    _os.unlink(filename)
                 return dir
             except (OSError, IOError) as e:
                 if e.args[0] != _errno.EEXIST:

Lib/test/test_tempfile.py

@@ -1,5 +1,7 @@
 # tempfile.py unit tests.
 import tempfile
+import errno
+import io
 import os
 import signal
 import sys
@@ -211,8 +213,48 @@ class test__candidate_tempdir_list(TC):
 
 test_classes.append(test__candidate_tempdir_list)
 
+# We test _get_default_tempdir some more by testing gettempdir.
 
-# We test _get_default_tempdir by testing gettempdir.
+class TestGetDefaultTempdir(TC):
+    """Test _get_default_tempdir()."""
+
+    def test_no_files_left_behind(self):
+        # use a private empty directory
+        with tempfile.TemporaryDirectory() as our_temp_directory:
+            # force _get_default_tempdir() to consider our empty directory
+            def our_candidate_list():
+                return [our_temp_directory]
+
+            with support.swap_attr(tempfile, "_candidate_tempdir_list",
+                                   our_candidate_list):
+                # verify our directory is empty after _get_default_tempdir()
+                tempfile._get_default_tempdir()
+                self.assertEqual(os.listdir(our_temp_directory), [])
+
+                def raise_OSError(*args, **kwargs):
+                    raise OSError(-1)
+
+                with support.swap_attr(io, "open", raise_OSError):
+                    # test again with failing io.open()
+                    with self.assertRaises(IOError) as cm:
+                        tempfile._get_default_tempdir()
+                    self.assertEqual(cm.exception.args[0], errno.ENOENT)
+                    self.assertEqual(os.listdir(our_temp_directory), [])
+
+                open = io.open
+                def bad_writer(*args, **kwargs):
+                    fp = open(*args, **kwargs)
+                    fp.write = raise_OSError
+                    return fp
+
+                with support.swap_attr(io, "open", bad_writer):
+                    # test again with failing write()
+                    with self.assertRaises(IOError) as cm:
+                        tempfile._get_default_tempdir()
+                    self.assertEqual(cm.exception.errno, errno.ENOENT)
+                    self.assertEqual(os.listdir(our_temp_directory), [])
+
+test_classes.append(TestGetDefaultTempdir)
 
 
 class test__get_candidate_names(TC):