From 557b54aa60e9abbb93e5737512d9963e640f2d1f Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Mon, 26 Apr 2021 10:42:16 -0700
Subject: [PATCH] Fix crash on docstrings ending with "\ " (#2142)
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Co-authored-by: Łukasz Langa <lukasz@langa.pl>
---
 CHANGES.md              |  2 ++
 src/black/__init__.py   |  8 +++++++-
 tests/data/docstring.py | 31 +++++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/CHANGES.md b/CHANGES.md
index 9fe6b7e..814956c 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -4,6 +4,8 @@
 
 #### _Black_
 
+- Fix crash on docstrings ending with "\ ". (#2142)
+
 - Reflect the `--skip-magic-trailing-comma` and `--experimental-string-processing` flags
   in the name of the cache file. Without this fix, changes in these flags would not take
   effect if the cache had already been populated. (#2131)
diff --git a/src/black/__init__.py b/src/black/__init__.py
index 99afc7d..051de5d 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -2186,7 +2186,13 @@ class LineGenerator(Visitor[Line]):
                 if docstring[0] == quote_char:
                     docstring = " " + docstring
                 if docstring[-1] == quote_char:
-                    docstring = docstring + " "
+                    docstring += " "
+                if docstring[-1] == "\\":
+                    backslash_count = len(docstring) - len(docstring.rstrip("\\"))
+                    if backslash_count % 2:
+                        # Odd number of tailing backslashes, add some padding to
+                        # avoid escaping the closing string quote.
+                        docstring += " "
             else:
                 # Add some padding if the docstring is empty.
                 docstring = " "
diff --git a/tests/data/docstring.py b/tests/data/docstring.py
index 9e1c244..ee6d0c0 100644
--- a/tests/data/docstring.py
+++ b/tests/data/docstring.py
@@ -158,6 +158,22 @@ def docstring_with_inline_tabs_and_tab_indentation():
 	"""
 	pass
 
+
+def backslash_space():
+    """\ """
+
+
+def multiline_backslash_1():
+  '''
+  hey\there\
+  \ '''
+
+
+def multiline_backslash_2():
+  '''
+  hey there \ '''
+
+
 # output
 
 class MyClass:
@@ -316,3 +332,18 @@ def docstring_with_inline_tabs_and_tab_indentation():
     line ends with some tabs
     """
     pass
+
+
+def backslash_space():
+    """\ """
+
+
+def multiline_backslash_1():
+    """
+  hey\there\
+  \ """
+
+
+def multiline_backslash_2():
+    """
+    hey there \ """
-- 
2.39.5