Trailing comma prevents multiline -> single line

[jbnjohnathan]

Describe the bug A clear and concise description of what the bug is.
When a python file contains a line split over several lines, which should be one line black does not compress it into one line if there is a trailing comma.

To Reproduce Steps to reproduce the behavior:

This code:

responseObject = jsonify(
    {
        "status": "success"
    }
)

Will be formatted to:

responseObject = jsonify({"status": "success"})

This is expected behaviour.

But if there is a trailing comma like this:

responseObject = jsonify(
    {
        "status": "success",
    }
)

The code will not be changed.

Expected behavior A clear and concise description of what you expected to happen.
I expect black to move the multiline statement to one line if the line will not be too long, regardless of the trailing comma.

Environment (please complete the following information):

• Version: 20.8b1
• OS and Python version: [e.g. Ubuntu/Python 3.6.9]

Does this bug also happen on master? To answer this, you have two options:
Yes it happens on master, tested with https://black.now.sh/?version=master

Additional context Add any other context about the problem here.

[MarcoGorelli]

Is this the same as #1742 ?

[jbnjohnathan]

Is this the same as #1742 ?

Ah yes indeed! Then this one can be closed as a duplicate