gh-58451: Add optional delete_on_close parameter to NamedTemporaryFile (GH-97015)

Lib/test/test_tempfile.py

@@ -11,6 +11,7 @@ import contextlib
 import stat
 import types
 import weakref
+import gc
 from unittest import mock
 
 import unittest
@@ -1013,6 +1014,102 @@ class TestNamedTemporaryFile(BaseTestCase):
                 pass
         self.assertRaises(ValueError, use_closed)
 
+    def test_context_man_not_del_on_close_if_delete_on_close_false(self):
+        # Issue gh-58451: tempfile.NamedTemporaryFile is not particulary useful
+        # on Windows
+        # A NamedTemporaryFile is NOT deleted when closed if
+        # delete_on_close=False, but is deleted on context manager exit
+        dir = tempfile.mkdtemp()
+        try:
+            with tempfile.NamedTemporaryFile(dir=dir,
+                                             delete=True,
+                                             delete_on_close=False) as f:
+                f.write(b'blat')
+                f_name = f.name
+                f.close()
+                with self.subTest():
+                    # Testing that file is not deleted on close
+                    self.assertTrue(os.path.exists(f.name),
+                            f"NamedTemporaryFile {f.name!r} is incorrectly "
+                            f"deleted on closure when delete_on_close=False")
+
+            with self.subTest():
+                # Testing that file is deleted on context manager exit
+                self.assertFalse(os.path.exists(f.name),
+                                 f"NamedTemporaryFile {f.name!r} exists "
+                                 f"after context manager exit")
+
+        finally:
+            os.rmdir(dir)
+
+    def test_context_man_ok_to_delete_manually(self):
+        # In the case of delete=True, a NamedTemporaryFile can be manually
+        # deleted in a with-statement context without causing an error.
+        dir = tempfile.mkdtemp()
+        try:
+            with tempfile.NamedTemporaryFile(dir=dir,
+                                             delete=True,
+                                             delete_on_close=False) as f:
+                f.write(b'blat')
+                f.close()
+                os.unlink(f.name)
+
+        finally:
+            os.rmdir(dir)
+
+    def test_context_man_not_del_if_delete_false(self):
+        # A NamedTemporaryFile is not deleted if delete = False
+        dir = tempfile.mkdtemp()
+        f_name = ""
+        try:
+            # Test that delete_on_close=True has no effect if delete=False.
+            with tempfile.NamedTemporaryFile(dir=dir, delete=False,
+                                             delete_on_close=True) as f:
+                f.write(b'blat')
+                f_name = f.name
+            self.assertTrue(os.path.exists(f.name),
+                        f"NamedTemporaryFile {f.name!r} exists after close")
+        finally:
+            os.unlink(f_name)
+            os.rmdir(dir)
+
+    def test_del_by_finalizer(self):
+        # A NamedTemporaryFile is deleted when finalized in the case of
+        # delete=True, delete_on_close=False, and no with-statement is used.
+        def my_func(dir):
+            f = tempfile.NamedTemporaryFile(dir=dir, delete=True,
+                                            delete_on_close=False)
+            tmp_name = f.name
+            f.write(b'blat')
+            # Testing extreme case, where the file is not explicitly closed
+            # f.close()
+            return tmp_name
+        # Make sure that the garbage collector has finalized the file object.
+        gc.collect()
+        dir = tempfile.mkdtemp()
+        try:
+            tmp_name = my_func(dir)
+            self.assertFalse(os.path.exists(tmp_name),
+                        f"NamedTemporaryFile {tmp_name!r} "
+                        f"exists after finalizer ")
+        finally:
+            os.rmdir(dir)
+
+    def test_correct_finalizer_work_if_already_deleted(self):
+        # There should be no error in the case of delete=True,
+        # delete_on_close=False, no with-statement is used, and the file is
+        # deleted manually.
+        def my_func(dir)->str:
+            f = tempfile.NamedTemporaryFile(dir=dir, delete=True,
+                                            delete_on_close=False)
+            tmp_name = f.name
+            f.write(b'blat')
+            f.close()
+            os.unlink(tmp_name)
+            return tmp_name
+        # Make sure that the garbage collector has finalized the file object.
+        gc.collect()
+
     def test_bad_mode(self):
         dir = tempfile.mkdtemp()
         self.addCleanup(os_helper.rmtree, dir)
@@ -1081,7 +1178,8 @@ class TestSpooledTemporaryFile(BaseTestCase):
         missing_attrs = iobase_attrs - spooledtempfile_attrs
         self.assertFalse(
             missing_attrs,
-            'SpooledTemporaryFile missing attributes from IOBase/BufferedIOBase/TextIOBase'
+            'SpooledTemporaryFile missing attributes from '
+            'IOBase/BufferedIOBase/TextIOBase'
         )
 
     def test_del_on_close(self):