Update constructor formatting to match MS Style guide

[cmeeren]

Issue created from fantomas-online

Code

This is how it's formatted with AlternativeLongMemberDefinitions = true:

type SomeVeryLongTypeNameWithConstructor
    (
        aVeryLongType: AVeryLongTypeThatYouNeedToUse,
        aSecondVeryLongType: AVeryLongTypeThatYouNeedToUse,
        aThirdVeryLongType: AVeryLongTypeThatYouNeedToUse
    )
    =
    class
    end

Result

This is how it's formatted with AlternativeLongMemberDefinitions = false (the current default):

type SomeVeryLongTypeNameWithConstructor(aVeryLongType: AVeryLongTypeThatYouNeedToUse,
                                         aSecondVeryLongType: AVeryLongTypeThatYouNeedToUse,
                                         aThirdVeryLongType: AVeryLongTypeThatYouNeedToUse) =
    class
    end

Problem description

This is a violation of the "avoid name-sensitive alignment" clause of the F# code formatting guidelines.

Se also the F# code formatting guidelines, section Place parameters on a new line for long definitions. It demonstrates how this concrete case should be formatted:

type TC
    (
        aVeryLongCtorParam: AVeryLongTypeThatYouNeedToUse,
        aSecondVeryLongCtorParam: AVeryLongTypeThatYouNeedToUse,
        aThirdVeryLongCtorParam: AVeryLongTypeThatYouNeedToUse
    ) =
    // ... the body of the class follows

Based on this, I suggest that AlternativeLongMemberDefinitions should be true by default.

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 at 01/09/2021 08:58:25 - ca42f0d

Default Fantomas configuration

[nojaf]

The setting should not be changed or impacted in any way here.
The default style for constructors should be updated to match the MS style guide.
The rule of thumb is that is that the default Fantomas settings should adhere to the MS guide.

AlternativeLongMemberDefinitions tailors specifically to the GR guide.
The only remaining difference between the guides (at the time of writing) is the location of the = sign.
MS puts it after the ), while GR places it on a new line.

The existing way Fantomas formats it does not adhere to either style and that is the bug to me.

[cmeeren]

The setting should not be changed or impacted in any way here.
The default style for constructors should be updated to match the MS style guide.

Makes sense 👍

MS puts it after the ), while GR places it on a new line.

Actually, the official guide is inconsistent about this particular point (at least in the case of there being a return type annotation): dotnet/docs#22296

The existing way Fantomas formats it does not adhere to either style and that is the bug to me.

I agree.

[nojaf]

Thanks for starting the conversation at dotnet/docs.