Exception - detect of multiple defines when define surrounds a DU member

[theimowski]

Issue created from fantomas-online

Code

type A =
  | B of int
  | C

#if DEBUG
  with
    member this.GetB =
      match this with
      | B x -> x
      | _ -> failwith "shouldn't happen"
#endif

Error

System.Exception: Fantomas is trying to format the input multiple times due to the detect of multiple defines.
There is a problem with merging all the code back togheter. Please raise an issue at https://github.com/fsprojects/fantomas/issues.
   at Microsoft.FSharp.Core.PrintfModule.PrintFormatToStringThenFail@1433.Invoke(String message) in D:\workspace\_work\1\s\src\fsharp\FSharp.Core\printf.fs:line 1433
   at Fantomas.String.merge(String a, String b) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/Utils.fs:line 62
   at Microsoft.FSharp.Collections.ListModule.Fold[T,TState](FSharpFunc`2 folder, TState state, FSharpList`1 list) in D:\workspace\_work\1\s\src\fsharp\FSharp.Core\list.fs:line 222
   at Microsoft.FSharp.Collections.ListModule.Reduce[T](FSharpFunc`2 reduction, FSharpList`1 list) in D:\workspace\_work\1\s\src\fsharp\FSharp.Core\list.fs:line 234
   at Fantomas.CodeFormatterImpl.format@408-1.Invoke(Tuple`3[] _arg1) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/CodeFormatterImpl.fs:line 417
   at Microsoft.FSharp.Control.AsyncPrimitives.CallThenInvokeNoHijackCheck[a,b](AsyncActivation`1 ctxt, FSharpFunc`2 userCode, b result1) in D:\workspace\_work\1\s\src\fsharp\FSharp.Core\async.fs:line 404
   at Microsoft.FSharp.Control.Trampoline.Execute(FSharpFunc`2 firstAction) in D:\workspace\_work\1\s\src\fsharp\FSharp.Core\async.fs:line 104

Problem description

Removing the preprocessor directive fixes the isse

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 03/03/2021 07:40:00 - e92fa7a

    { config with
                IndentSize = 2 }

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

[nojaf]

Thanks for your recent reports Tomasz. I've looked at all of them and none are really trivial to solve I'm afraid.
Perhaps over time, I see more opportunities to fix the others as well.

[theimowski]

They are quite edge cases, multiple preprocessor directives probably don't help.
On a side note, I've found these type of conditionals making code harder to maintain and strive to refactor towards getting rid of them wherever possible.