Exception whilst trying to pickle a DirectoryInfo in a .NET Framework application

[JackMatusiewicz]

Description

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Trying to serialise a DirectoryInfo succeeds in a .NET Core app but fails in a .NET Framework app

Code

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open MBrace.FsPickler
open MBrace.FsPickler.Json
open System.IO

let makeDirectoryInfoPickler (resolver : IPicklerResolver) =
    let stringPickler = resolver.Resolve<string> ()

    let read (r : ReadState) =
        stringPickler.Read r "DirectoryInfo" |> DirectoryInfo

    let write (w : WriteState) (d : DirectoryInfo) =
        stringPickler.Write w "DirectoryInfo" d.FullName

    Pickler.FromPrimitives (read,write)

[<EntryPoint>]
let main _ =
    let di = DirectoryInfo "test"

    let registry = CustomPicklerRegistry ()
    registry.RegisterFactory makeDirectoryInfoPickler
    let cache = PicklerCache.FromCustomPicklerRegistry registry
    let jser = FsPickler.CreateJsonSerializer(picklerResolver = cache)
    di |> jser.PickleToString |> printfn "%s"
    0

Expected behavior

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Identical behaviour between .NET Core and .NET Framework, ideally with it working in both.

Actual behavior

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Crashes in .NET framework with the following stack trace:

MBrace.FsPickler.NonSerializableTypeException
  HResult=0x80131500
  Message=Type 'System.IO.DirectoryInfo' is not serializable.
  Source=FSharp.Core
  StackTrace:
   at Microsoft.FSharp.Core.Operators.Raise[T](Exception exn)
   at MBrace.FsPickler.PicklerCache.GeneratePickler[T]() in C:\Users\source\repos\FsPicklerTest\FsPicklerTest\FsPickler-5.2\src\FsPickler\PicklerGeneration\PicklerCache.fs:line 64
   at MBrace.FsPickler.FsPicklerTextSerializer.Serialize[T](TextWriter writer, T value, FSharpOption`1 pickler, FSharpOption`1 streamingContext, FSharpOption`1 leaveOpen) in C:\Users\source\repos\FsPicklerTest\FsPicklerTest\FsPickler-5.2\src\FsPickler\FsPickler\TextSerializer.fs:line 35
   at <StartupCode$FsPickler>[email protected](TextWriter m, T v) in C:\source\repos\FsPicklerTest\FsPicklerTest\FsPickler-5.2\src\FsPickler\FsPickler\TextSerializer.fs:line 122
   at MBrace.FsPickler.FsPicklerTextSerializer.PickleToString[T](T value, FSharpOption`1 pickler, FSharpOption`1 streamingContext)
   at Program.main(String[] _arg1) in Program.fs:line 27

Current Findings

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I did some investigating into this, it seems the cause is that 'isUnsupportedType' inside PicklerGenerator.fs checks the type to see if IsMarshalByRef is set. In the .NET framework app it is set to true. However, in .NET Core it is not.

Related information

Operating system - Windows 10
Target F# runtime 4.4.3.0 (4.1)
.NET Framework 4.7.1
.NET Core 2.0
FsPickler 5.2.0
FsPickler.Json 5.2.0

[komadori]

Hi @eiriktsarpalis,

It looks like this issue should be fixed now that you've merged PR #106 . Do you have any idea how long it will be before an FsPickler release will include this change?

Thanks, Robin.