Why set splitted as all elements on new line?

[zaz600]

Black v18.9b0

Playground link

Options

--line-length=60
--pyi

Input

KEYS1 = {"aaaaa", "aaaaa", "aaaaa", "aaaaa", "aaaaa"}

KEYS2 = {"aaaaa", "aaaaa", "aaaaa", "aaaaa", "aaaaa", "aaaaa"}

Output

KEYS1 = {"aaaaa", "aaaaa", "aaaaa", "aaaaa", "aaaaa"}

KEYS2 = {
    "aaaaa",
    "aaaaa",
    "aaaaa",
    "aaaaa",
    "aaaaa",
    "aaaaa",
}

Expected

Something like this

KEYS1 = {"aaaaa", "aaaaa", "aaaaa", "aaaaa", "aaaaa"}

KEYS2 = {
    "aaaaa", "aaaaa", "aaaaa", "aaaaa", "aaaaa", 
    "aaaaa"
}

[zaz600]

Problem

Base code

KEYS1 = {"aaaaa", "aaaaa", "aaaaa", "aaaaa", "aaaaa"}

Alice make changes

KEYS1 = {"aaaaa", "aaaaa", "aaaaa", "aaaaa", "bbbbb"}

Alice format code with black:

KEYS1 = {"aaaaa", "aaaaa", "aaaaa", "aaaaa", "bbbbb"}

Bob make changes

KEYS1 = {"aaaaa", "aaaaa", "aaaaa", "aaaaa", "aaaaa", "ccccc"}

Bob format code with black:

KEYS1 = {
    "aaaaa",
    "aaaaa",
    "aaaaa",
    "aaaaa",
    "aaaaa",
    "ccccc",
}

We have ugly merge conflict of two changes

[peterjc]

Seems related to #601 ?

[nicktimko]

In your example, the list was made longer, so you could extend that to making the list arbitrarily long. In that case, the solutions would seem to be one of

• never break lists onto multiple lines
• always break lists (basically ignoring the line-length)
• look at the repository history and/or remember the past state of each variable (possibly also be sensitive to the number of committers?)

[reagle]

Sometimes I have similar structures, such as a list of a couple dozen words, or a hundred integers, and black forces them each to their own line, which is ghastly, as is the case in the third line:

ARTICLES = {'a', 'an', 'the'}
CONJUNCTIONS = {'and', 'but', 'nor', 'or'}
SHORT_PREPOSITIONS = {'among', 'as', 'at', 'by', 'for', 'from', 'in',
                      'of', 'on', 'out', 'per', 'to', 'upon', 'with', }

becomes:

ARTICLES = {"a", "an", "the"}
CONJUNCTIONS = {"and", "but", "nor", "or"}
SHORT_PREPOSITIONS = {
    "among",
    "as",
    "at",
    "by",
    "for",
    "from",
    "in",
    "of",
    "on",
    "out",
    "per",
    "to",
    "upon",
    "with",
}

Is this what it is supposed to do? Is there something I can do to prevent this?

[nicktimko]

@reagle I'd do one of the following:

1. If it's small-ish and you want to keep it with other code

# fmt: off
LONG_LIST_OF_STUFF = { ... }
# fmt: on

2. If it's large-ish, put those vars in their own source file and either:

   • prefix the file with # fmt: off
   • add the file to tool.black.exclude in pyproject.toml.

3. If it's gigantic, I'd store it in another format (text, JSON, etc.) and load it.

[reagle]

@nicktimko, thanks. I had searched the documentation for "disable" and "suspend" but hadn't come across # fmt: off.

[zsol]

As explained in the comments above, this is the intended behavior, and you can opt code out using # fmt: off and # fmt: on pairs.