https://github.com/python/cpython/commit/23a3e892ee34484676ec3d4ba683ff747e74e778
commit: 23a3e892ee34484676ec3d4ba683ff747e74e778
branch: 3.13
author: Miss Islington (bot) <31488909+miss-isling...@users.noreply.github.com>
committer: pablogsal <pablog...@gmail.com>
date: 2025-08-03T16:58:49Z
summary:
[3.13] gh-137314: Fix incorrect treatment of format specs in raw fstrings
(GH-137328) (#137345)
gh-137314: Fix incorrect treatment of format specs in raw fstrings (GH-137328)
(cherry picked from commit 0153d82a5ab0c6ac16c046bdd4438ea11b58d59d)
Co-authored-by: Pablo Galindo Salgado <pablog...@gmail.com>
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2025-08-02-23-04-57.gh-issue-137314.wjEdzD.rst
M Lib/test/test_fstring.py
M Parser/action_helpers.c
M Parser/lexer/lexer.c
M Parser/lexer/state.h
diff --git a/Lib/test/test_fstring.py b/Lib/test/test_fstring.py
index c2ab603a8a775c..5e743d34d2a573 100644
--- a/Lib/test/test_fstring.py
+++ b/Lib/test/test_fstring.py
@@ -1821,6 +1821,34 @@ def test_newlines_in_format_specifiers(self):
for case in valid_cases:
compile(case, "<string>", "exec")
+ def test_raw_fstring_format_spec(self):
+ # Test raw f-string format spec behavior (Issue #137314).
+ #
+ # Raw f-strings should preserve literal backslashes in format
specifications,
+ # not interpret them as escape sequences.
+ class UnchangedFormat:
+ """Test helper that returns the format spec unchanged."""
+ def __format__(self, format):
+ return format
+
+ # Test basic escape sequences
+ self.assertEqual(f"{UnchangedFormat():\xFF}", 'ÿ')
+ self.assertEqual(rf"{UnchangedFormat():\xFF}", '\\xFF')
+
+ # Test nested expressions with raw/non-raw combinations
+ self.assertEqual(rf"{UnchangedFormat():{'\xFF'}}", 'ÿ')
+ self.assertEqual(f"{UnchangedFormat():{r'\xFF'}}", '\\xFF')
+ self.assertEqual(rf"{UnchangedFormat():{r'\xFF'}}", '\\xFF')
+
+ # Test continuation character in format specs
+ self.assertEqual(f"""{UnchangedFormat():{'a'\
+ 'b'}}""", 'ab')
+ self.assertEqual(rf"""{UnchangedFormat():{'a'\
+ 'b'}}""", 'ab')
+
+ # Test multiple format specs in same raw f-string
+ self.assertEqual(rf"{UnchangedFormat():\xFF} {UnchangedFormat():\n}",
'\\xFF \\n')
+
if __name__ == '__main__':
unittest.main()
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2025-08-02-23-04-57.gh-issue-137314.wjEdzD.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2025-08-02-23-04-57.gh-issue-137314.wjEdzD.rst
new file mode 100644
index 00000000000000..09d0c3e68fc1ed
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2025-08-02-23-04-57.gh-issue-137314.wjEdzD.rst
@@ -0,0 +1,5 @@
+Fixed a regression where raw f-strings incorrectly interpreted
+escape sequences in format specifications. Raw f-strings now properly preserve
+literal backslashes in format specs, matching the behavior from Python 3.11.
+For example, ``rf"{obj:\xFF}"`` now correctly produces ``'\\xFF'`` instead of
+``'ÿ'``. Patch by Pablo Galindo.
diff --git a/Parser/action_helpers.c b/Parser/action_helpers.c
index 99dd0976c6137d..6f841ef2e4f9c3 100644
--- a/Parser/action_helpers.c
+++ b/Parser/action_helpers.c
@@ -1,6 +1,7 @@
#include <Python.h>
#include "pegen.h"
+#include "lexer/state.h"
#include "string_parser.h"
#include "pycore_runtime.h" // _PyRuntime
#include "pycore_pystate.h" // _PyInterpreterState_GET()
@@ -1369,7 +1370,15 @@ expr_ty _PyPegen_decoded_constant_from_token(Parser* p,
Token* tok) {
if (PyBytes_AsStringAndSize(tok->bytes, &bstr, &bsize) == -1) {
return NULL;
}
- PyObject* str = _PyPegen_decode_string(p, 0, bstr, bsize, tok);
+
+ // Check if we're inside a raw f-string for format spec decoding
+ int is_raw = 0;
+ if (INSIDE_FSTRING(p->tok)) {
+ tokenizer_mode *mode = TOK_GET_MODE(p->tok);
+ is_raw = mode->f_string_raw;
+ }
+
+ PyObject* str = _PyPegen_decode_string(p, is_raw, bstr, bsize, tok);
if (str == NULL) {
return NULL;
}
diff --git a/Parser/lexer/lexer.c b/Parser/lexer/lexer.c
index d29b0bbd25d2ab..384239bd414c38 100644
--- a/Parser/lexer/lexer.c
+++ b/Parser/lexer/lexer.c
@@ -22,22 +22,6 @@
|| c == '_'\
|| (c >= 128))
-#ifdef Py_DEBUG
-static inline tokenizer_mode* TOK_GET_MODE(struct tok_state* tok) {
- assert(tok->tok_mode_stack_index >= 0);
- assert(tok->tok_mode_stack_index < MAXFSTRINGLEVEL);
- return &(tok->tok_mode_stack[tok->tok_mode_stack_index]);
-}
-static inline tokenizer_mode* TOK_NEXT_MODE(struct tok_state* tok) {
- assert(tok->tok_mode_stack_index >= 0);
- assert(tok->tok_mode_stack_index + 1 < MAXFSTRINGLEVEL);
- return &(tok->tok_mode_stack[++tok->tok_mode_stack_index]);
-}
-#else
-#define TOK_GET_MODE(tok) (&(tok->tok_mode_stack[tok->tok_mode_stack_index]))
-#define TOK_NEXT_MODE(tok)
(&(tok->tok_mode_stack[++tok->tok_mode_stack_index]))
-#endif
-
#define MAKE_TOKEN(token_type) _PyLexer_token_setup(tok, token, token_type,
p_start, p_end)
#define MAKE_TYPE_COMMENT_TOKEN(token_type, col_offset, end_col_offset) (\
_PyLexer_type_comment_token_setup(tok, token, token_type,
col_offset, end_col_offset, p_start, p_end))
diff --git a/Parser/lexer/state.h b/Parser/lexer/state.h
index 9ed3babfdbfbf1..d8791d89dd02db 100644
--- a/Parser/lexer/state.h
+++ b/Parser/lexer/state.h
@@ -1,6 +1,7 @@
#ifndef _PY_LEXER_H_
#define _PY_LEXER_H_
+#include "Python.h"
#include "object.h"
#define MAXINDENT 100 /* Max indentation level */
@@ -138,5 +139,20 @@ void _PyTokenizer_Free(struct tok_state *);
void _PyToken_Free(struct token *);
void _PyToken_Init(struct token *);
+#ifdef Py_DEBUG
+static inline tokenizer_mode* TOK_GET_MODE(struct tok_state* tok) {
+ assert(tok->tok_mode_stack_index >= 0);
+ assert(tok->tok_mode_stack_index < MAXFSTRINGLEVEL);
+ return &(tok->tok_mode_stack[tok->tok_mode_stack_index]);
+}
+static inline tokenizer_mode* TOK_NEXT_MODE(struct tok_state* tok) {
+ assert(tok->tok_mode_stack_index >= 0);
+ assert(tok->tok_mode_stack_index + 1 < MAXFSTRINGLEVEL);
+ return &(tok->tok_mode_stack[++tok->tok_mode_stack_index]);
+}
+#else
+#define TOK_GET_MODE(tok) (&(tok->tok_mode_stack[tok->tok_mode_stack_index]))
+#define TOK_NEXT_MODE(tok)
(&(tok->tok_mode_stack[++tok->tok_mode_stack_index]))
+#endif
#endif
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