Trailing whitespace not preserved in docstring

[chebee7i]

Describe the bug Trailing whitespace in docstrings is not preserved.

To Reproduce Steps to reproduce the behavior:

$ cat -E demo.py
def func():$
    """$
    Line with trailing whitespace    $
$
    Another line with trailing whitespace    $
$
    Done.$
    """$
    pass$

$ black demo.py
error: cannot format demo.py: INTERNAL ERROR: Black produced code that is not equivalent to the source.  Please report a bug on https://github.com/psf/black/issues.  This diff might be helpful: /tmp/blk_geo3qids.log
Oh no! 💥 💔 💥
1 file failed to reformat.

$ cat /tmp/blk_geo3qids.log
--- src
+++ dst
@@ -16,11 +16,11 @@
       body=
         Expr(
           value=
             Constant(
               value=
-                'Line with trailing whitespace    \n\n Another line with trailing whitespace    \n\n Done.',  # str
+                'Line with trailing whitespace\n\n Another line with trailing whitespace\n\n Done.',  # str
             )  # /Constant
         )  # /Expr
         Pass(
         )  # /Pass
       decorator_list=

Expected behavior Trailing whitespace should be preserved or black should not complain.

Environment (please complete the following information):

• Version: 9171535 (HEAD of master as of today)
• OS and Python version: [e.g. Linux/Python 3.7.6]

Does this bug also happen on master?

It does happen on master. However, it does not happen at https://black.now.sh/?version=master. I'm not sure if that editor might be deleting the trailing whitespace?

[JelleZijlstra]

#1417 fixed a very similar crash, are you sure you are running on current master?

[chebee7i]

Pretty sure. Just reconfirmed again on the new HEAD of master.

$ cat -E demo.py
def func():$
    """$
    Line with trailing whitespace    $
$
    Another line with trailing whitespace    $
$
    Done.$
    """$
    pass$

$ python -c "import black; print(black.__version__)"
19.10b1.dev1+g3461338

$ git log -n 1 HEAD
commit 34613383abad9afa5cc1b3945e50bbfca13d036e (HEAD -> master, upstream/master, upstream/HEAD)
Author: Richard Si <63936253+ichard26@users.noreply.github.com>
Date:   Tue May 26 22:42:07 2020 -0400

    Make 'python -m black' work (#1460)

$ python -m black demo.py
error: cannot format demo.py: INTERNAL ERROR: Black produced code that is not equivalent to the source.  Please report a bug on https://github.com/psf/black/issues.  This diff might be helpful: /tmp/blk_c_1s9bnx.log
Oh no! 💥 💔 💥
1 file failed to reformat.

$ cat /tmp/blk_c_1s9bnx.log
--- src
+++ dst
@@ -16,11 +16,11 @@
       body=
         Expr(
           value=
             Constant(
               value=
-                'Line with trailing whitespace    \n\n Another line with trailing whitespace    \n\n Done.',  # str
+                'Line with trailing whitespace\n\n Another line with trailing whitespace\n\n Done.',  # str
             )  # /Constant
         )  # /Expr
         Pass(
         )  # /Pass
       decorator_list=

[chebee7i]

This is a regression from 19.3b0. Is it possible to get a quick fix out for this? I originally upgraded while trying to get around #875, but I had to revert due to the above issues. If more complicated to fix, no prob.

[Jackenmen]

You did not say this happens on 19.10b0 in issue description 🤔

[chebee7i]

Actually, this does not seem to be happening on 19.10b0. My apologies!

[ichard26]

This also doesn't happen on 20.08b1 and therefore I will close this issue now.

(black-rHKUX7ap) R:\Programming\black>black temp.py --diff --color
--- temp.py     2020-08-30 16:41:16.245384 +0000
+++ temp.py     2020-08-30 16:41:33.472229 +0000
@@ -1,9 +1,9 @@
 def func():
     """
-    Line with trailing whitespace
+    Line with trailing whitespace

-    Another line with trailing whitespace
+    Another line with trailing whitespace

     Done.
     """
     pass
would reformat temp.py
All done! ✨ 🍰 ✨
1 file would be reformatted.

Environment:

• Black version: Black 20.08b1
• Python version: CPython 3.8.1
• OS version: Windows 10 Home Edition Build 18363