From 7f3678885fc7ab6f9fb1749f6d2a8ed3468841f3 Mon Sep 17 00:00:00 2001
From: Zsolt Dollenstein <zsol.zsol@gmail.com>
Date: Thu, 7 Jun 2018 20:41:34 +0200
Subject: [PATCH] fix handling of empty triple quoted strings (#314)

---
 README.md                   | 1 +
 black.py                    | 2 +-
 tests/data/string_quotes.py | 2 ++
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 411c9bf..580607f 100644
--- a/README.md
+++ b/README.md
@@ -813,6 +813,7 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
 
 * fixed improper unmodified file caching when `-S` was used
 
+* fixed formatting of empty triple quoted strings (#313)
 
 ### 18.6b1
 
diff --git a/black.py b/black.py
index dd7fe39..1d2f1a3 100644
--- a/black.py
+++ b/black.py
@@ -2546,7 +2546,7 @@ def normalize_string_quotes(leaf: Leaf) -> None:
             leaf.value = f"{prefix}{orig_quote}{body}{orig_quote}"
         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 new_quote == '"""' and new_body[-1] == '"':
+    if new_quote == '"""' and new_body[-1:] == '"':
         # edge case:
         new_body = new_body[:-1] + '\\"'
     orig_escape_count = body.count("\\")
diff --git a/tests/data/string_quotes.py b/tests/data/string_quotes.py
index 1ac6b06..807f866 100644
--- a/tests/data/string_quotes.py
+++ b/tests/data/string_quotes.py
@@ -1,3 +1,4 @@
+''''''
 '\''
 '"'
 "'"
@@ -45,6 +46,7 @@ re.compile(r'[\\"]')
 
 # output
 
+""""""
 "'"
 '"'
 "'"
-- 
2.39.2