Disable Black formatting of dict expression within mapping comprehensions

I'm currently researching Black as our default formatter, but, I'm having some edge cases that don't format well and I want to know if there's a way to get the result I want.

Black's documentation partially explores my problem, I have a dictionary expression spread horizontally, and I want to keep it that way since I'm expecting lines to be added, e.g.:

# Black would keep this as-is because of the trailing comma
TRANSLATIONS = {
    "en_us": "English (US)",
    "pl_pl": "polski",
}

But in my case the dictionary is inside a list comprehension:

res = [
    {
        'id': item.id,
        'name': item.name,
    }
    for item in items.select()
]

Which Black collapses, regardless of the trailing comma, like so:

res = [
    {"id": item.id, "name": item.name,}
    for item in items.select()
]

Is there a way of telling Black to retain the horizontal structure in these cases?

Solution

It seems that black addressed this issue.

At the time of writing this answer, using black version 20.8b1, the formatting is done as I was hoping for.

As long as there is a magic trailing comma on the last item in the dictionary expression, black will format the code within the list comprehension.

res = [
    {
        "id": item.id, "name": item.name,
    }
    for item in items.select()
]

Will format to:

res = [
    {
        "id": item.id,
        "name": item.name,
    }
    for item in items.select()
]