gh-104018: disallow "z" format specifier in %-format of byte strings (GH-104033)

PEP-0682 specified that %-formatting would not support the "z" specifier,
but it was unintentionally allowed for bytes. This PR makes use of the "z"
flag an error for %-formatting in a bytestring.

Issue: #104018

---------

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>

diff --git a/Lib/test/test_format.py b/Lib/test/test_format.py
index 69b0d5f1c5a5157c510cee9548154cfbb450e494..6fa49dbc0b730ca8380f0c804e0faa22534ea566 100644 (file)
--- a/Lib/test/test_format.py
+++ b/Lib/test/test_format.py
@@ -619,6 +619,8 @@ class FormatTest(unittest.TestCase):
         error_msg = re.escape("unsupported format character 'z'")
         with self.assertRaisesRegex(ValueError, error_msg):
             "%z.1f" % 0  # not allowed in old style string interpolation
+        with self.assertRaisesRegex(ValueError, error_msg):
+            b"%z.1f" % 0
 
 
 if __name__ == "__main__":

diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-05-01-12-03-52.gh-issue-104018.PFxGS4.rst b/Misc/NEWS.d/next/Core and Builtins/2023-05-01-12-03-52.gh-issue-104018.PFxGS4.rst
new file mode 100644 (file)
index 0000000..f3cadae
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2023-05-01-12-03-52.gh-issue-104018.PFxGS4.rst
@@ -0,0 +1 @@
+Disallow the "z" format specifier in %-format of bytes objects.

diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index 27b2ad4f2cb38f215709a172d52333404cfa9e25..e7e85cc19cda75e9b464c6acee0b295c6bbd251a 100644 (file)
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -705,7 +705,6 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
                 case ' ': flags |= F_BLANK; continue;
                 case '#': flags |= F_ALT; continue;
                 case '0': flags |= F_ZERO; continue;
-                case 'z': flags |= F_NO_NEG_0; continue;
                 }
                 break;
             }