pythongh-129958: New syntax error in format spec applies to both f-strings and t-strings (python#135570)

Co-authored-by: Tomas R. <[email protected]>
Co-authored-by: Lysandros Nikolaou <[email protected]>

Author: 3 people

Lib/test/test_tstring.py

@@ -219,6 +219,7 @@ def test_syntax_errors(self):
             ("t'{lambda:1}'", "t-string: lambda expressions are not allowed "
                               "without parentheses"),
             ("t'{x:{;}}'", "t-string: expecting a valid expression after '{'"),
+            ("t'{1:d\n}'", "t-string: newlines are not allowed in format specifiers")
         ):
             with self.subTest(case), self.assertRaisesRegex(SyntaxError, err):
                 eval(case)

Misc/NEWS.d/next/Core_and_Builtins/2025-06-24-06-41-47.gh-issue-129958.EaJuS0.rst

@@ -0,0 +1,2 @@
+Differentiate between t-strings and f-strings in syntax error for newlines
+in format specifiers of single-quoted interpolated strings.

Parser/lexer/lexer.c

@@ -1421,7 +1421,8 @@ tok_get_fstring_mode(struct tok_state *tok, tokenizer_mode* current_tok, struct
                     return MAKE_TOKEN(
                         _PyTokenizer_syntaxerror(
                             tok,
-                            "f-string: newlines are not allowed in format specifiers for single quoted f-strings"
+                            "%c-string: newlines are not allowed in format specifiers for single quoted %c-strings",
+                            TOK_GET_STRING_PREFIX(tok), TOK_GET_STRING_PREFIX(tok)
                         )
                     );
                 }