Anonymous types in a DU inserts newlines

[ly29]

Issue created from fantomas-online

Code

type A =
    | A of int
    | B of {| B: int ; C : string; Karlar: byte ; Kalle: byte|}
    | C of string

Result

type A =
    | A of int
    | B of


            {| B: int
               C: string
               Karlar: byte
               Kalle: byte |}
    | C of string

Problem description

Please describe here the Fantomas problem you encountered.
Check out our Contribution Guidelines.

Extra information

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

Options

Fantomas main branch at 2022-11-10T07:58:47Z - 573d273

Default Fantomas configuration

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

[nojaf]

Hello, thank you for reporting this issue.

I believe the problem is introduced around:

fantomas/src/Fantomas.Core/CodePrinter.fs

Lines 3484 to 3485 in 18a97bd

	+> (opt sepColon so genIdent +> autoIndentAndNlnIfExpressionExceedsPageWidth t
	|> optSingle (genTriviaFor SynField_IdentifierAndType) innerRange)

autoIndentAndNlnIfExpressionExceedsPageWidth t should only be considered when there is an named identifier present.

Changing this behaviour to:

    +> (match so with
        | None -> t
        | Some name -> genIdent name +> sepColon +> autoIndentAndNlnIfExpressionExceedsPageWidth t
        |> optSingle (genTriviaFor SynField_IdentifierAndType) innerRange)

probably does the trick.
Are you interested in submitting a PR for this?

[ly29]

Probably tomorrow I can have a go

[ly29]

Also thank you for your quick feedback!

[ly29]

Yeah that does the trick, I will try submitting the PR tomorrow.

any guidance for where place the test and should there be more than one test for this fix?

[nojaf]

I think adding a single test to src/Fantomas.Core.Tests/UnionTests.fs would suffice in this case.
Please take all our guidelines into account.
Many thanks!