Idempotency problem when using lower MaxLineLength than default and fantomas needs to split lines

[knocte]

Issue created from fantomas-online

Formatted code

namespace FSX.Infrastructure

module Unix =

    let GrabTheFirstStringBeforeTheFirstColon (lines: seq<string>) =
        seq {
            for line in lines do
                yield (line.Split([| ":" |], StringSplitOptions.RemoveEmptyEntries)).[0]
        }

Reformatted code

namespace FSX.Infrastructure

module Unix =

    let GrabTheFirstStringBeforeTheFirstColon (lines: seq<string>) =
        seq {
            for line in lines do
                yield
                    ((line.Split(
                        [| ":" |],
                        StringSplitOptions.RemoveEmptyEntries
                    ))).[0]
        }

Expected result

namespace FSX.Infrastructure

module Unix =

    let GrabTheFirstStringBeforeTheFirstColon (lines: seq<string>) =
        seq {
            for line in lines do
                yield
                    (line.Split(
                        [| ":" |],
                        StringSplitOptions.RemoveEmptyEntries
                    )).[0]
        }

Problem description

Fantomas was not able to produce the same code after reformatting the result (note, the bug doesn't happen if MaxLineLength=120), adding unnecessary parentheses.

Extra information

• The formatted result breaks by code.
• The formatted result gives compiler warnings.
• I or my company would be willing to help fix this.

Options

Fantomas master branch at 2022-03-29T09:12:14Z - 8f2ab14

    { config with
                MaxLineLength = 80 }

_{Did you know that you can ignore files when formatting from fantomas-tool or the FAKE targets by using a .fantomasignore file?}

[nojaf]

The additional introduced parentheses are probably part of a last resort measure to produce valid code.
I agree this is a bug, I'm going to mark it stylistic but it can be fixed against the master branch.

[knocte]

I'm going to mark it stylistic

AFAIU, idempotency problems are never marked as stylistic. Please note that this is not just superflous addition of parentheses: if you run fantomas 3 times, 3 pairs of parentheses are added.