No more allow mode 'w'/'x'

- File is not truncated in mode 'w'/'x', which results non-shrinked file.
- This cannot be simply resolved by adding truncation for mode 'w'/'x', which may be used on an unseekable file buffer and truncation is not allowed.

Author: danny0838

Doc/library/zipfile.rst

@@ -523,7 +523,7 @@ ZipFile Objects
    Removes a member from the archive.  *zinfo_or_arcname* is either the full
    path of the member, or a :class:`ZipInfo` instance.
 
-   The archive must be opened with mode ``'w'``, ``'x'`` or ``'a'``.
+   The archive must be opened with mode ``'a'``.
 
    Calling :meth:`remove` on a closed ZipFile will raise a :exc:`ValueError`.
 

Lib/test/test_zipfile/test_core.py

@@ -1503,6 +1503,23 @@ def test_verify(self):
                     zh.remove(file)
                 mock_fn.assert_not_called()
 
+        # mode 'w': error and do nothing
+        with zipfile.ZipFile(TESTFN, 'w', self.compression) as zh:
+            zh.writestr(file, data)
+            with mock.patch('zipfile.ZipFile._remove_members') as mock_fn:
+                with self.assertRaises(ValueError):
+                    zh.remove(file)
+                mock_fn.assert_not_called()
+
+        # mode 'x': error and do nothing
+        os.remove(TESTFN)
+        with zipfile.ZipFile(TESTFN, 'x', self.compression) as zh:
+            zh.writestr(file, data)
+            with mock.patch('zipfile.ZipFile._remove_members') as mock_fn:
+                with self.assertRaises(ValueError):
+                    zh.remove(file)
+                mock_fn.assert_not_called()
+
         # mode 'a': the most general use case
         with zipfile.ZipFile(TESTFN, 'w', self.compression) as zh:
             zh.writestr(file, data)
@@ -1531,21 +1548,6 @@ def test_verify(self):
                     zh.remove(zinfo)
                 mock_fn.assert_not_called()
 
-        # mode 'w': like 'a'; allows removing a just written member
-        with zipfile.ZipFile(TESTFN, 'w', self.compression) as zh:
-            zh.writestr(file, data)
-            with mock.patch('zipfile.ZipFile._remove_members') as mock_fn:
-                zh.remove(file)
-                mock_fn.assert_called_once_with({zh.getinfo(file)})
-
-        # mode 'x': like 'w'
-        os.remove(TESTFN)
-        with zipfile.ZipFile(TESTFN, 'x', self.compression) as zh:
-            zh.writestr(file, data)
-            with mock.patch('zipfile.ZipFile._remove_members') as mock_fn:
-                zh.remove(file)
-                mock_fn.assert_called_once_with({zh.getinfo(file)})
-
     def test_zip64(self):
         """Test if members use zip64."""
         file = 'datafile.txt'

Lib/zipfile/__init__.py

@@ -1867,10 +1867,13 @@ def extractall(self, path=None, members=None, pwd=None):
             self._extract_member(zipinfo, path, pwd)
 
     def remove(self, zinfo_or_arcname):
-        """Remove a member from the archive."""
+        """Remove a member from the archive.
 
-        if self.mode not in ('w', 'x', 'a'):
-            raise ValueError("remove() requires mode 'w', 'x', or 'a'")
+        The archive must be open with mode 'a', since mode 'w'/'x' may be used
+        on an unseekable file buffer, which disallows truncation."""
+
+        if self.mode != 'a':
+            raise ValueError("remove() requires mode 'a'")
         if not self.fp:
             raise ValueError(
                 "Attempt to write to ZIP archive that was already closed")