pythongh-125008: Fix tokenize.untokenize roundtrip for \n{{ (pyth…

…onGH-125013) (cherry picked from commit db23b8b) Co-authored-by: Tomas R. <[email protected]>
miss-islington · Oct 6, 2024 · acc2968 · acc2968
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diff --git a/Lib/test/test_tokenize.py b/Lib/test/test_tokenize.py
@@ -1916,6 +1916,26 @@ def test_roundtrip(self):
         self.check_roundtrip(r"f'\\\\N{{'")
         self.check_roundtrip(r"f'\\\\\\N{{'")
         self.check_roundtrip(r"f'\\\\\\\\N{{'")
+
+        self.check_roundtrip(r"f'\n{{foo}}'")
+        self.check_roundtrip(r"f'\\n{{foo}}'")
+        self.check_roundtrip(r"f'\\\n{{foo}}'")
+        self.check_roundtrip(r"f'\\\\n{{foo}}'")
+
+        self.check_roundtrip(r"f'\t{{foo}}'")
+        self.check_roundtrip(r"f'\\t{{foo}}'")
+        self.check_roundtrip(r"f'\\\t{{foo}}'")
+        self.check_roundtrip(r"f'\\\\t{{foo}}'")
+
+        self.check_roundtrip(r"rf'\t{{foo}}'")
+        self.check_roundtrip(r"rf'\\t{{foo}}'")
+        self.check_roundtrip(r"rf'\\\t{{foo}}'")
+        self.check_roundtrip(r"rf'\\\\t{{foo}}'")
+
+        self.check_roundtrip(r"rf'\{{foo}}'")
+        self.check_roundtrip(r"f'\\{{foo}}'")
+        self.check_roundtrip(r"rf'\\\{{foo}}'")
+        self.check_roundtrip(r"f'\\\\{{foo}}'")
         cases = [
     """
 if 1:

diff --git a/Lib/tokenize.py b/Lib/tokenize.py
@@ -202,7 +202,7 @@ def escape_brackets(self, token):
                         characters[-2::-1]
                     )
                 )
-                if n_backslashes % 2 == 0:
+                if n_backslashes % 2 == 0 or characters[-1] != "N":
                     characters.append(character)
                 else:
                     consume_until_next_bracket = True

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2024-10-05-23-53-06.gh-issue-125008.ETANpd.rst b/Misc/NEWS.d/next/Core_and_Builtins/2024-10-05-23-53-06.gh-issue-125008.ETANpd.rst
@@ -0,0 +1,2 @@
+Fix :func:`tokenize.untokenize` producing invalid syntax for
+double braces preceded by certain escape characters.