Class type with long variable names results in invalid formatted F# code

[Bobface]

Issue created from fantomas-online

The formatted result for the code below is invalid F# code: The variables in the result are missing a comma , at the end of their corresponding lines.

@nojaf I would like to work on a PR which implements the commas at the end of the lines. Let me know if you agree with this fix.

Edit: It seems like there is already a test in TypeDeclarationTests which checks for this behaviour:

[<Test>]
let ``long constructors should have parameters on separate lines`` () =
    formatSourceString false """type C (aVeryLongType : AVeryLongTypeThatYouNeedToUse, aSecondVeryLongType : AVeryLongTypeThatYouNeedToUse, aThirdVeryLongType : AVeryLongTypeThatYouNeedToUse) =
    member this.X = 42
"""  ({ config with SpaceBeforeClassConstructor = true })
    |> prepend newline
    |> should equal """
type C (
    aVeryLongType: AVeryLongTypeThatYouNeedToUse
    aSecondVeryLongType: AVeryLongTypeThatYouNeedToUse
    aThirdVeryLongType: AVeryLongTypeThatYouNeedToUse)
    =
    member this.X = 42
"""

However it also checks for the wrong result.

Code

type SomeType(looooooooooooooooooooooooong1: string, looooooooooooooooooooooooong2: string, looooooooooooooooooooooooong3: string -> string) =
    member this.SomeMethod () =
        "..."

Error

Fantomas was able to format the code but the result appears to be invalid F# code.
Please open an issue.

Formatted result:

type SomeType(
    looooooooooooooooooooooooong1: string
    looooooooooooooooooooooooong2: string
    looooooooooooooooooooooooong3: string -> string)
    =
    member this.SomeMethod() = "..."

Options

Fantomas Next - 4.0.0-alpha-001-1/1/1990

Name	Value
IndentSpaceNum	4
PageWidth	120
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

[knocte]

I think this is a regression introduced by this commit: ef2e6f3

[knocte]

The culprit of the regression is that the unit test is actually wrong, it's missing commas. This is something I noticed myself in G-Research coding guidelines and I fixed with a PR here:

G-Research/fsharp-formatting-conventions#1

[nojaf]

Hey @Bobface and @knocte, good catch. I just copied that example from the G-Research style guide and missed the comma's.

We need them in this case, so @Bobface it would be great if you could work on a fix.
I'm guessing the fix will be changing sepNln here.
Not sure though, can't look into great detail now.

[Bobface]

@nojaf Yep that one worked for the member tuples but not for the constructor tuples. Am currently looking into where the constructors tuples are implemented.

[nojaf]

Probably around https://github.com/fsprojects/fantomas/blob/master/src/Fantomas/CodePrinter.fs#L2527