string prefixes: don't normalise capital R-strings (#1271)

Resolves #1244

Co-authored-by: Łukasz Langa <lukasz@langa.pl>

diff --git a/black.py b/black.py
index 69d24c54133320e3cd7b6c8e0a17cc3c23f17981..b7cacf7767855ec903578b5be7499d526f1d542f 100644 (file)
--- a/black.py
+++ b/black.py
@@ -2842,7 +2842,7 @@ def normalize_string_prefix(leaf: Leaf, remove_u_prefix: bool = False) -> None:
     match = re.match(r"^([furbFURB]*)(.*)$", leaf.value, re.DOTALL)
     assert match is not None, f"failed to match string {leaf.value!r}"
     orig_prefix = match.group(1)
-    new_prefix = orig_prefix.lower()
+    new_prefix = orig_prefix.replace("F", "f").replace("B", "b").replace("U", "u")
     if remove_u_prefix:
         new_prefix = new_prefix.replace("u", "")
     leaf.value = f"{new_prefix}{match.group(2)}"

diff --git a/tests/data/string_prefixes.py b/tests/data/string_prefixes.py
index fbad5e0704ffb249dc759a16beb5a3efb0b62e43..0ca3686a2b6c0fee3004c0e78c066b24b1b0c5a1 100644 (file)
--- a/tests/data/string_prefixes.py
+++ b/tests/data/string_prefixes.py
@@ -3,12 +3,16 @@
 name = R"Łukasz"
 F"hello {name}"
 B"hello"
+r"hello"
+fR"hello"
 
 # output
 
 
 #!/usr/bin/env python3.6
 
-name = r"Łukasz"
+name = R"Łukasz"
 f"hello {name}"
 b"hello"
+r"hello"
+fR"hello"