gh-91760: More strict rules for numerical group references and group names in RE (GH-91792)

Only sequence of ASCII digits is now accepted as a numerical reference.
The group name in bytes patterns and replacement strings can now only
contain ASCII letters and digits and underscore.

2 files changed, 21 insertions, 8 deletions

diff --git a/Doc/library/re.rst b/Doc/library/re.rst
index 3cd9f25..39e7d23 100644
--- a/Doc/library/re.rst
+++ b/Doc/library/re.rst
@@ -395,7 +395,8 @@ The special characters are:
 ``(?P<name>...)``
    Similar to regular parentheses, but the substring matched by the group is
    accessible via the symbolic group name *name*.  Group names must be valid
-   Python identifiers, and each group name must be defined only once within a
+   Python identifiers, and in bytes patterns they must contain only characters
+   in the ASCII range.  Each group name must be defined only once within a
    regular expression.  A symbolic group is also a numbered group, just as if
    the group were not named.
 
@@ -417,8 +418,9 @@ The special characters are:
    |                                       | * ``\1``                         |
    +---------------------------------------+----------------------------------+
 
-   .. deprecated:: 3.11
-      Group names containing non-ASCII characters in bytes patterns.
+   .. versionchanged:: 3.12
+      In bytes patterns group names must contain only characters in
+      the ASCII range.
 
 .. index:: single: (?P=; in regular expressions
 
@@ -489,8 +491,8 @@ The special characters are:
    will match with ``'<user@host.com>'`` as well as ``'user@host.com'``, but
    not with ``'<user@host.com'`` nor ``'user@host.com>'``.
 
-   .. deprecated:: 3.11
-      Group *id* containing anything except ASCII digits.
+   .. versionchanged:: 3.12
+      Group *id* can only contain ASCII digits.
 
 
 The special sequences consist of ``'\'`` and a character from the list below.
@@ -1001,9 +1003,10 @@ form.
       Empty matches for the pattern are replaced when adjacent to a previous
       non-empty match.
 
-   .. deprecated:: 3.11
-      Group *id* containing anything except ASCII digits.
-      Group names containing non-ASCII characters in bytes replacement strings.
+   .. versionchanged:: 3.12
+      Group *id* can only contain ASCII digits.
+      In bytes replacement strings group names must contain only characters
+      in the ASCII range.
 
 
 .. function:: subn(pattern, repl, string, count=0, flags=0)
diff --git a/Doc/whatsnew/3.12.rst b/Doc/whatsnew/3.12.rst
index dacf041..b73c3db 100644
--- a/Doc/whatsnew/3.12.rst
+++ b/Doc/whatsnew/3.12.rst
@@ -114,3 +114,13 @@ Porting to Python 3.12
 
 This section lists previously described changes and other bugfixes
 that may require changes to your code.
+
+Changes in the Python API
+-------------------------
+
+* More strict rules are now applied for numerical group references and
+  group names in regular expressions.
+  Only sequence of ASCII digits is now accepted as a numerical reference.
+  The group name in bytes patterns and replacement strings can now only
+  contain ASCII letters and digits and underscore.
+  (Contributed by Serhiy Storchaka in :gh:`91760`.)