Black removing extra spaces in docstrings. Breaking markdown formatting

[cazador481]

When a docstring is formatted using markdown, an extra space at the end means that the next line is not to be wrapped. (pydoc3 uses markdown). Unfortunately, black removes the extra space, which causes markdown renders to not do what they are supposed to.

Example code that gets miss rendered. Note: I am using a _ to denote a space at the end of the line.
Original

def boo():
    """Halloween.

    This is not supposed to be wrapped._ 
    New text
    """

After running black:

def boo():
    """Halloween.

    This is not supposed to be wrapped.
    New text
    """

Expected:

def boo():
    """Halloween.

    This is not supposed to be wrapped._
    New text
    """

Environment

• Black's version: 22.8.0
• OS and Python version: linux: 3.9.13

[felix-hilden]

Right, this is definitely intentional, tracing all the way back to #1053. I'd say it's desirable in most cases, but not sure about this one.

[pawamoy]

Unfortunately that's the only way to break a line in common Markdown (two trailing spaces), apart from using <br> 😕

Is Black assuming a specific markup for docstrings?

[pawamoy]

In fact CommonMark says that we can use a backslash instead of trailing spaces.

For those using Python-Markdown / MkDocs, it has been asked before: Python-Markdown/markdown#1157.
Suggested solution: use the pymdownx.escapeall extension, with the hardbreak option enabled:

markdown_extensions:
- pymdownx.escapeall:
    hardbreak: yes