Possible wrong indentation for functions with parameters over multiple lines

[Bobface]

Issue created from fantomas-online

The parameters to the function might have invalid indentation after formatting. The problem is that the formatted result below adheres to the F#-Styleguide (see Place parameters on a new line for long member definitions) while the compiler prints indentation warnings when compiling:

warning FS0058: Possibly wrong indentation: This token is displaced compared to the context beginning at position (xx:xx). Increase the indentation for this token or use the standard formatting conventions.

(roughly translated)

The compiler wants the parameters to be aligned with the braces, for example:

type T(A: string, B: string, C: string) = ....

(* to *)

type T(A: string,
       B: string,
       C: string) =
....

The first parameter can either be in a new line or the same line as the opening brace. The equals sign can either be on the same line as the closing brace or on a new line. I personally see the example above as the cleanest way.

Code

type VersionMismatchDuringDeserializationException (message: string, innerException: Exception) =
    inherit DeserializationException(message, innerException)

Result

type VersionMismatchDuringDeserializationException(
    message: string,
    innerException: Exception)
    =
    inherit DeserializationException(message, innerException)

Options

Fantomas Master at 05/24/2020 18:24:52 - c23aa74

Name	Value
IndentSpaceNum	4
PageWidth	80
SemicolonAtEndOfLine	false
SpaceBeforeParameter	true
SpaceBeforeLowercaseInvocation	true
SpaceBeforeUppercaseInvocation	false
SpaceBeforeClassConstructor	false
SpaceBeforeMember	false
SpaceBeforeColon	false
SpaceAfterComma	true
SpaceBeforeSemicolon	false
SpaceAfterSemicolon	true
IndentOnTryWith	false
SpaceAroundDelimiter	true
MaxIfThenElseShortWidth	40
MaxInfixOperatorExpression	50
MaxRecordWidth	40
MaxArrayOrListWidth	40
MaxLetBindingWidth	40
MultilineBlockBracketsOnSameColumn	false
NewlineBetweenTypeDefinitionAndMembers	false
KeepIfThenInSameLine	false
StrictMode	false

[Bobface]

@nojaf Is it OK if I begin to fix this as proposed before we get a response from dotnet?

[knocte]

Get a response? The maximum they could do is propose a compiler change to make it not spit the warning (even if I bet that they will just change the style-guide), but that would take ages until fantomas users get the fix, so I think fantomas should adopt the warning-less approach for now.

[nojaf]

@Bobface please wait, I'm still checking with some other people.

[knocte]

@nojaf given that this problem was introduced in the latest alphas (regression), can we get clarity before 4.0 final is released? to give enough room to fix

[nojaf]

@knocte I discussed this with @jindraivanek and we came up with a proposal.
Still trying to get a hold of @Smaug123 to verify on GR side.

[nojaf]

Outcome to resolve these issues would be the following:

type VersionMismatchDuringDeserializationException
    (message: string,
     innerException: System.Exception)
    =
    inherit System.Exception(message, innerException)

type C() =
    member _.LongMethodWithLotsOfParameters
        (aVeryLongType: int,
         aSecondVeryLongType: int,
         aThirdVeryLongType: int)
        : int
        =
        aVeryLongType + aSecondVeryLongType + aThirdVeryLongType

I'm willing to tackle these myself, once time permits it.

[nojaf]

@knocte I got a rely on the MS style guide.
They envision things rather different than what I suggested.
So I think I'll go for the MS solution out of the box.
And the GR approach behind a setting (in a later PR).

[knocte]

That's good stuff, I actually like both MS and GR solutions, not sure which one I'll end up using.