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

dylwil3 · tomasr8 · lysnikolaou · web-flow · commit fb9e292919d8 · 2025-06-26T15:02:50.000+02:00
Co-authored-by: Tomas R. &lt;tomas.roun8@gmail.com&gt;
Co-authored-by: Lysandros Nikolaou &lt;lisandrosnik@gmail.com&gt;
diff --git a/Lib/test/test_tstring.py b/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)
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-06-24-06-41-47.gh-issue-129958.EaJuS0.rst b/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.
diff --git a/Parser/lexer/lexer.c b/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)
                         )
                     );
                 }

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+Differentiate between t-strings and f-strings in syntax error for newlines`
	`2`	`+in format specifiers of single-quoted interpolated strings.`
Original file line number	Diff line number	Diff line change
`@@ -1421,7 +1421,8 @@ tok_get_fstring_mode(struct tok_state tok, tokenizer_mode current_tok, struct`
`1421`	`1421`	`return MAKE_TOKEN(`
`1422`	`1422`	`_PyTokenizer_syntaxerror(`
`1423`	`1423`	`tok,`
`1424`		`- "f-string: newlines are not allowed in format specifiers for single quoted f-strings"`
	`1424`	`+ "%c-string: newlines are not allowed in format specifiers for single quoted %c-strings",`
	`1425`	`+ TOK_GET_STRING_PREFIX(tok), TOK_GET_STRING_PREFIX(tok)`
`1425`	`1426`	`)`
`1426`	`1427`	`);`
`1427`	`1428`	`}`