gh-131492, gh-131461: handle exceptions in GzipFile constructor while owning resources (#131462)

Co-authored-by: Victor Stinner <vstinner@python.org>

Lib/gzip.py

@@ -202,6 +202,8 @@ class GzipFile(_compression.BaseStream):
             raise ValueError("Invalid mode: {!r}".format(mode))
         if mode and 'b' not in mode:
             mode += 'b'
+
+        try:
             if fileobj is None:
                 fileobj = self.myfileobj = builtins.open(filename, mode or 'rb')
             if filename is None:
@@ -247,6 +249,11 @@ class GzipFile(_compression.BaseStream):
 
             if self.mode == WRITE:
                 self._write_gzip_header(compresslevel)
+        except:
+            # Avoid a ResourceWarning if the write fails,
+            # eg read-only file or KeyboardInterrupt
+            self._close()
+            raise
 
     @property
     def mtime(self):
@@ -387,9 +394,12 @@ class GzipFile(_compression.BaseStream):
             elif self.mode == READ:
                 self._buffer.close()
         finally:
+            self._close()
+
+    def _close(self):
         self.fileobj = None
         myfileobj = self.myfileobj
-            if myfileobj:
+        if myfileobj is not None:
             self.myfileobj = None
             myfileobj.close()
 

Lib/test/test_tarfile.py

@@ -19,6 +19,7 @@ from test import archiver_tests
 from test import support
 from test.support import os_helper
 from test.support import script_helper
+from test.support import warnings_helper
 
 # Check for our compression modules.
 try:
@@ -1638,8 +1639,11 @@ class WriteTest(WriteTestBase, unittest.TestCase):
                         raise exctype
 
             f = BadFile()
-            with self.assertRaises(exctype):
-                tar = tarfile.open(tmpname, self.mode, fileobj=f,
+            with (
+                warnings_helper.check_no_resource_warning(self),
+                self.assertRaises(exctype),
+            ):
+                tarfile.open(tmpname, self.mode, fileobj=f,
                              format=tarfile.PAX_FORMAT,
                              pax_headers={'non': 'empty'})
             self.assertFalse(f.closed)

Misc/NEWS.d/next/Library/2025-03-19-14-36-54.gh-issue-131461.uDUmdY.rst

@@ -0,0 +1 @@
+Fix :exc:`ResourceWarning` when constructing a :class:`gzip.GzipFile` in write mode with a broken file object.

Misc/NEWS.d/next/Library/2025-03-20-08-32-49.gh-issue-131492.saC2cA.rst

@@ -0,0 +1 @@
+Fix a resource leak when constructing a :class:`gzip.GzipFile` with a filename fails, for example when passing an invalid ``compresslevel``.