Improve Python 2 only syntax detection (GH-2592)

[etc/vim.git] / src / black / strings.py

diff --git a/src/black/strings.py b/src/black/strings.py
index 80f588f5119c4432c4a43ce8414b014893b4be2b..d7b6c240e80215ef1c268634433074d82e4c5aeb 100644 (file)
--- a/src/black/strings.py
+++ b/src/black/strings.py
@@ -190,9 +190,9 @@ def normalize_string_quotes(s: str) -> str:
     if "f" in prefix.casefold():
         matches = re.findall(
             r"""
-            (?:[^{]|^)\{  # start of the string or a non-{ followed by a single {
+            (?:(?<!\{)|^)\{  # start of the string or a non-{ followed by a single {
                 ([^{].*?)  # contents of the brackets except if begins with {{
-            \}(?:[^}]|$)  # A } followed by end of the string or a non-}
+            \}(?:(?!\})|$)  # A } followed by end of the string or a non-}
             """,
             new_body,
             re.VERBOSE,