Fix instability due to trailing comma logic (#2572)

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

diff --git a/src/black/strings.py b/src/black/strings.py
index 262c2ba4313bee09839008f59bf49d4d26543dc6..9d0e2eb8430e538efcba96582dcfc9ee2d4bc468 100644 (file)
--- a/src/black/strings.py
+++ b/src/black/strings.py
@@ -149,6 +149,10 @@ def normalize_string_prefix(s: str) -> str:
         .replace("U", "")
         .replace("u", "")
     )
         .replace("U", "")
         .replace("u", "")
     )

+
+    # Python syntax guarantees max 2 prefixes and that one of them is "r"
+    if len(new_prefix) == 2 and "r" != new_prefix[0].lower():
+        new_prefix = new_prefix[::-1]

     return f"{new_prefix}{match.group(2)}"
 
 
     return f"{new_prefix}{match.group(2)}"