Unhandled Exception: ... invalid name ... at LiteDB.BsonDocument.set_Item in 'mutable' field

The mutable attribute avoids insert in LiteDB, or passing through Json’s encoder, something happens that the name of the field is modified.

open System
open LiteDB
open LiteDB.FSharp

[<StructuredFormatDisplay("a{SizeGb}GB")>]
[<CLIMutable>]
type Disk = 
    { SizeGb : int }

[<StructuredFormatDisplay("Computer #{Id}: {Manufacturer}/{DiskCount}/{Disks}")>]
[<CLIMutable>]
type Computer =
    { Id: int
      mutable Manufacturer: string
      mutable Disks: Disk list }
    [<BsonIgnore>] 
    member __.DiskCount = __.Disks.Length  // property calculated

[<EntryPoint>]
let main argv =

    let myPc =
        { Id = 0
          Manufacturer = "Computers Inc."
          Disks =
            [ { SizeGb = 100 }
              { SizeGb = 250 }
              { SizeGb = 500 } ] }
    printfn "%A" myPc

    let mapper = FSharpBsonMapper()
    use db = new LiteDatabase("data.db", mapper)
    let computers = db.GetCollection<Computer>("computers")

    // All right , but if I remove the comment on next line I get the error
    // computers.Insert(myPc) |> ignore
    myPc.Manufacturer <- "Dell"
    printfn "%A" myPc
    ...

The field you are trying to modify Manufacturer seems to change its name Manufacturer@' The full error is:

Unhandled Exception: System.ArgumentException: Field 'Manufacturer@' has an invalid name.
   at LiteDB.BsonDocument.set_Item(String name, BsonValue value)
   at LiteDB.JsonReader.ReadObject()
   at LiteDB.JsonReader.ReadValue(JsonToken token)
   at LiteDB.JsonSerializer.Deserialize(String json)
   at LiteDB.FSharp.Bson.serialize[t](t entity)
   at LiteDB.FSharp.FSharpBsonMapper.ToDocument[t](t entity)
   at LiteDB.LiteCollection`1.Insert(T document)
   at Program.main(String[] argv) in /app/Program.fs:line ..

Thanks

[Zaid-Ajaj]

Fixed and released in version 2.8.0 to nuget, should be available really soon when nuget does it’s magic. Now I decided to take control of how the fields are marshalled, so now these mutable records will work just fine 😄

[Zaid-Ajaj]

Hmm even though it is not recommended, I don’t see an issue in supporting mutable constructs in the library, I will work on it…