From cf2282d6e848f1e1ad5e804c7e18abc0acc4c9c2 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Mon, 26 Apr 2021 07:54:14 -0700
Subject: [PATCH 1/3] Fix crash on docstrings ending with "\ "

Fixes #2136
---
 CHANGES.md              | 2 ++
 src/black/__init__.py   | 8 +++++++-
 tests/data/docstring.py | 8 ++++++++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/CHANGES.md b/CHANGES.md
index aa08396e491..769f01ea13e 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 00d3729c835..f9bd6a3414b 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -2179,7 +2179,13 @@ def visit_STRING(self, leaf: Leaf) -> Iterator[Line]:
                 indent = " " * 4 * self.current_line.depth
                 docstring = fix_docstring(docstring, indent)
             else:
-                docstring = docstring.strip()
+                new_docstring = docstring.strip()
+                # If the docstring ended with "\ ", stripping away the space
+                # will be a syntax error. Just put the trailing space back.
+                if new_docstring.endswith("\\"):
+                    docstring = docstring.lstrip()
+                else:
+                    docstring = new_docstring
 
             if docstring:
                 # Add some padding if the docstring starts / ends with a quote mark.
diff --git a/tests/data/docstring.py b/tests/data/docstring.py
index 9e1c2441e0e..fade592127a 100644
--- a/tests/data/docstring.py
+++ b/tests/data/docstring.py
@@ -158,6 +158,10 @@ def docstring_with_inline_tabs_and_tab_indentation():
 	"""
 	pass
 
+
+def backslash_space():
+    """\ """
+
 # output
 
 class MyClass:
@@ -316,3 +320,7 @@ def docstring_with_inline_tabs_and_tab_indentation():
     line ends with some tabs
     """
     pass
+
+
+def backslash_space():
+    """\ """

From 03889695d68df8323c8df372b3fbd52237dd2f50 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Mon, 26 Apr 2021 08:56:36 -0700
Subject: [PATCH 2/3] add a test case

---
 tests/data/docstring.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tests/data/docstring.py b/tests/data/docstring.py
index fade592127a..8bf5b9aedbd 100644
--- a/tests/data/docstring.py
+++ b/tests/data/docstring.py
@@ -162,6 +162,12 @@ def docstring_with_inline_tabs_and_tab_indentation():
 def backslash_space():
     """\ """
 
+
+def multiline_backslash():
+  '''
+  hey\there\
+  \ '''
+
 # output
 
 class MyClass:
@@ -324,3 +330,9 @@ def docstring_with_inline_tabs_and_tab_indentation():
 
 def backslash_space():
     """\ """
+
+
+def multiline_backslash():
+    """
+  hey\there\
+  \ """

From f5a5921a627491ad389c686b97afae4f08a52b7e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=81ukasz=20Langa?= <lukasz@langa.pl>
Date: Mon, 26 Apr 2021 19:13:41 +0200
Subject: [PATCH 3/3] Also handle multiline string docstrings

---
 src/black/__init__.py   | 16 ++++++++--------
 tests/data/docstring.py | 15 +++++++++++++--
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/src/black/__init__.py b/src/black/__init__.py
index f9bd6a3414b..7701a35e9d5 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -2179,20 +2179,20 @@ def visit_STRING(self, leaf: Leaf) -> Iterator[Line]:
                 indent = " " * 4 * self.current_line.depth
                 docstring = fix_docstring(docstring, indent)
             else:
-                new_docstring = docstring.strip()
-                # If the docstring ended with "\ ", stripping away the space
-                # will be a syntax error. Just put the trailing space back.
-                if new_docstring.endswith("\\"):
-                    docstring = docstring.lstrip()
-                else:
-                    docstring = new_docstring
+                docstring = docstring.strip()
 
             if docstring:
                 # Add some padding if the docstring starts / ends with a quote mark.
                 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 8bf5b9aedbd..ee6d0c051d7 100644
--- a/tests/data/docstring.py
+++ b/tests/data/docstring.py
@@ -163,11 +163,17 @@ def backslash_space():
     """\ """
 
 
-def multiline_backslash():
+def multiline_backslash_1():
   '''
   hey\there\
   \ '''
 
+
+def multiline_backslash_2():
+  '''
+  hey there \ '''
+
+
 # output
 
 class MyClass:
@@ -332,7 +338,12 @@ def backslash_space():
     """\ """
 
 
-def multiline_backslash():
+def multiline_backslash_1():
     """
   hey\there\
   \ """
+
+
+def multiline_backslash_2():
+    """
+    hey there \ """