KeepIndentInBranch not respected when returning short function application

[nojaf]

Issue created from fantomas-online

Code

let private parseModel (modelSrc: string) : Result<MyReturnType, string list> =
  if not (File.Exists(modelSrc)) then
    Error [ sprintf "Provided modelSrc \"%s\" does not exist" modelSrc ]
  else
    let graph = new QueryableGraph()
    graph.LoadFromFile(modelSrc, TurtleParser())

    let xsdPath =
      Path.Combine(Directory.GetCurrentDirectory(), "Some.xsd")

    let ontologyPath =
      Path.Combine(Directory.GetCurrentDirectory(), "Some.ttl")

    let ontoGraph = new OntologyGraph()
    FileLoader.Load(ontoGraph, ontologyPath)

    let validationErrors =
      GraphValidation.validate xsdPath ontoGraph "http://company.com/meh" graph

    if List.isEmpty validationErrors then
      Ok graph
    else
      Error validationErrors

Result

let private parseModel (modelSrc: string) : Result<MyReturnType, string list> =
    if not (File.Exists(modelSrc)) then
        Error [ sprintf "Provided modelSrc \"%s\" does not exist" modelSrc ]
    else
        let graph = new QueryableGraph()
        graph.LoadFromFile(modelSrc, TurtleParser())

        let xsdPath =
            Path.Combine(Directory.GetCurrentDirectory(), "Some.xsd")

        let ontologyPath =
            Path.Combine(Directory.GetCurrentDirectory(), "Some.ttl")

        let ontoGraph = new OntologyGraph()
        FileLoader.Load(ontoGraph, ontologyPath)

        let validationErrors =
            GraphValidation.validate xsdPath ontoGraph "http://company.com/meh" graph

        if List.isEmpty validationErrors then
            Ok graph
        else
            Error validationErrors

Problem description

This is a good example where AST alone is probably not sufficient enough to make the right call whether this should keep the indent.
@Smaug123 I'm correct that is should not indent the else branch right?

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 06/12/2021 10:31:17 - 8f71594

    { config with
                KeepIndentInBranch = true }

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

[Smaug123]

I agree, this should probably unindent. What's the problem that means the AST doesn't determine what to do here?

[nojaf]

Oh I mean when you have something like this:

Error [ sprintf "Provided modelSrc \"%s\" does not exist" modelSrc ]

the matching AST looks like

App
                (NonAtomic, false, Ident Error,
                 ArrayOrListOfSeqExpr
                   (false,
                    CompExpr
                      (true, { contents = true },
                       App
                         (NonAtomic, false,
                          App
                            (NonAtomic, false, Ident sprintf,
                             Const
                               (String
                                  ("Provided modelSrc "%s" does not exist",
                                   tmp.fsx (2,20--2,61) IsSynthetic=false),
                                tmp.fsx (2,20--2,61) IsSynthetic=false),
                             tmp.fsx (2,12--2,61) IsSynthetic=false),
                          Ident modelSrc, tmp.fsx (2,12--2,70) IsSynthetic=false),
                       tmp.fsx (2,12--2,70) IsSynthetic=false),
                    tmp.fsx (2,10--2,72) IsSynthetic=false),
                 tmp.fsx (2,4--2,72) IsSynthetic=false)

so a nested SynExpr.App shape and this is difficult to recognize as a short statement.
In this case, it is a oneliner, but it could also be longer like

Error 
    [ 
        sprintf "Provided modelSrc \"%s\" does not exist" modelSrc
        // some comment, same AST though
    ]

I'm guessing you would indent if the application was multiline.
Or not?

[nojaf]

I'm going to solve this purely based on AST.
I do think it makes sense as you are immediately returning a functional call as an expression.
So that does kinda counts as an early return to me.
We can discuss this further when new evidence pops up.