Don't introduce quotes to f-string sub-expressions on string boundaries (#871)

[etc/vim.git] / black.py

diff --git a/black.py b/black.py
index 7ede0b45f7908a11a453654a8d17145df60481f9..7629d9f4c2d23f09e45b16fdf83eb82f3bbf99a1 100644 (file)
--- a/black.py
+++ b/black.py
@@ -2728,7 +2728,15 @@ def normalize_string_quotes(leaf: Leaf) -> None:
         new_body = sub_twice(escaped_orig_quote, rf"\1\2{orig_quote}", new_body)
         new_body = sub_twice(unescaped_new_quote, rf"\1\\{new_quote}", new_body)
     if "f" in prefix.casefold():
-        matches = re.findall(r"[^{]\{(.*?)\}[^}]", new_body)
+        matches = re.findall(
+            r"""
+            (?:[^{]|^)\{  # 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-}
+            """,
+            new_body,
+            re.VERBOSE,
+        )
         for m in matches:
             if "\\" in str(m):
                 # Do not introduce backslashes in interpolated expressions