Getting a 'no Oak node is defined for this type' error when formatting a p/invoke signature with nullability annotations

[Numpsy]

I tried to use Fantomas online to report this, but got a github error about the URL being too long, so:

I tried to run Fantomas (both 7 and the 8 preview) on a new project at work and got the error

Failed to format file: .\src\Fortra.DCS.Metadata.FileSystem\XAttr.fs : no Oak node is defined for this type: App
  (LongIdent (SynLongIdent ([byte], [], [None])), None, [], [], None, false,
   (19,65--19,69))
At line 19, column 65 in tmp.fsx.

Which appears to be down to code like this

module private XAttrHandler =

    [<SupportedOSPlatform("macos")>]
    [<DllImport("/usr/lib/libSystem.dylib", EntryPoint = "getxattr", SetLastError = true)>]
    extern int64 private getxattrMacOs(string path, string name, byte[] | null value, uint64 size, uint32 position, int options)

If I try to format that in Fantomas online I get this error:

System.Exception: unexpected type: App
  (LongIdent (SynLongIdent ([byte], [], [None])), None, [], [], None, false,
   (5,65--5,69))
   at Fantomas.Core.ASTTransformer.mkType(CreationAide creationAide, SynType t) in /_//src/Fantomas.Core/ASTTransformer.fs:line 2419
   at Fantomas.Core.ASTTransformer.mkType(CreationAide creationAide, SynType t) in /_//src/Fantomas.Core/ASTTransformer.fs:line 2330
   at Fantomas.Core.ASTTransformer.mkType(CreationAide creationAide, SynType t) in /_//src/Fantomas.Core/ASTTransformer.fs:line 2418
   at Fantomas.Core.ASTTransformer.mkExternType@2007.Invoke(SynType t) in /_//src/Fantomas.Core/ASTTransformer.fs:line 2033
   at Fantomas.Core.ASTTransformer.mkExternPat@2036.Invoke(SynPat pat) in /_//src/Fantomas.Core/ASTTransformer.fs:line 2040
   at Microsoft.FSharp.Primitives.Basics.List.mapToFreshConsTail[a,b](FSharpList`1 cons, FSharpFunc`2 f, FSharpList`1 x) in D:\a\_work\1\s\src\fsharp\src\FSharp.Core\local.fs:line 240
   at Microsoft.FSharp.Primitives.Basics.List.map[T,TResult](FSharpFunc`2 mapping, FSharpList`1 x) in D:\a\_work\1\s\src\fsharp\src\FSharp.Core\local.fs:line 250
   at Microsoft.FSharp.Collections.ListModule.Map[T,TResult](FSharpFunc`2 mapping, FSharpList`1 list) in D:\a\_work\1\s\src\fsharp\src\FSharp.Core\list.fs:line 98
   at Fantomas.Core.ASTTransformer.mkExternBinding(CreationAide creationAide, SynBinding _arg8) in /_//src/Fantomas.Core/ASTTransformer.fs:line 2053
   at Fantomas.Core.ASTTransformer.mkModuleDecl(CreationAide creationAide, SynModuleDecl decl) in /_//src/Fantomas.Core/ASTTransformer.fs:line 2099
   at Fantomas.Core.ASTTransformer.mkModuleDecls@3278-5.Invoke(FSharpList`1 nodes) in /_//src/Fantomas.Core/ASTTransformer.fs:line 3278
   at Fantomas.Core.ASTTransformer.mkModuleDecl(CreationAide creationAide, SynModuleDecl decl) in /_//src/Fantomas.Core/ASTTransformer.fs:line 2113
   at Fantomas.Core.ASTTransformer.mkModuleDecls@3278-5.Invoke(FSharpList`1 nodes) in /_//src/Fantomas.Core/ASTTransformer.fs:line 3278
   at Fantomas.Core.ASTTransformer.mkModuleOrNamespace(CreationAide creationAide, SynModuleOrNamespace mn) in /_//src/Fantomas.Core/ASTTransformer.fs:line 3343
   at Fantomas.Core.ASTTransformer.mds@3353.Invoke(SynModuleOrNamespace mn)
   at Microsoft.FSharp.Primitives.Basics.List.map[T,TResult](FSharpFunc`2 mapping, FSharpList`1 x) in D:\a\_work\1\s\src\fsharp\src\FSharp.Core\local.fs:line 247
   at Microsoft.FSharp.Collections.ListModule.Map[T,TResult](FSharpFunc`2 mapping, FSharpList`1 list) in D:\a\_work\1\s\src\fsharp\src\FSharp.Core\list.fs:line 98
   at Fantomas.Core.ASTTransformer.mkImplFile(CreationAide creationAide, ParsedImplFileInput _arg15, Range m) in /_//src/Fantomas.Core/ASTTransformer.fs:line 3353
   at Fantomas.Core.ASTTransformer.mkOak(FSharpOption`1 sourceText, ParsedInput ast) in /_//src/Fantomas.Core/ASTTransformer.fs:line 3795
   at Fantomas.Core.CodeFormatterImpl.formatDocument@114-3.Invoke(Unit unitVar) in /_//src/Fantomas.Core/CodeFormatterImpl.fs:line 114
   at Microsoft.FSharp.Control.AsyncPrimitives.CallThenInvoke[T,TResult](AsyncActivation`1 ctxt, TResult result1, FSharpFunc`2 part2) in D:\a\_work\1\s\src\fsharp\src\FSharp.Core\async.fs:line 509
   at Microsoft.FSharp.Control.Trampoline.Execute(FSharpFunc`2 firstAction) in D:\a\_work\1\s\src\fsharp\src\FSharp.Core\async.fs:line 112

The error goes away if I change the byte[] | null to just byte[].

Thanks.

[nojaf]

Thanks for reporting this!

[nojaf]

Fix available in https://github.com/fsprojects/fantomas/releases/tag/v8.0.0-alpha-016

[Numpsy]

Thanks, I can confirm that the new version successfully formats the file that was failing before.