Question: Serializing records with sets and lists in F#

[bhandfast]

I'm using F# and I have trouble packing record types containing sets or lists.

The code below fails with the message:

"System.Runtime.Serialization.SerializationException: Type 'FSI_0003+SetRecord' does not have default (parameterless) public constructor."

I guess I need to write a new custom serializer that packs the values as arrays are packed but I'm not sure how? Any ideas or pointers to where I can find examples?

#r "MsgPack.dll"

type TestRecord = {
    Foo : string;
    Bar: int;
}

type OptionRecord = {
    Foo : string option;
    Bar: int;
}

let serializer = MsgPack.Serialization.SerializationContext.Default

let serializeToMsgPack<'T> (x:'T) = 
    serializer.GetSerializer<'T>().PackSingleObject(x)

// Gives result:

serializeToMsgPack { TestRecord.Foo = "Hello"; Bar = 42 }
serializeToMsgPack { OptionRecord.Foo = Some "Hello"; Bar = 42 }
serializeToMsgPack { OptionRecord.Foo = None; Bar = 42 }

type SetRecord = {
    Foo : string option;
    Bar: Set<int>;
}


// Crashes:
serializeToMsgPack { SetRecord.Foo = Some "Hello"; Bar = Set.empty.Add(42) }


type ListRecord = {
    Foo : string option;
    Bar: int list;
}

// Crashes:

serializeToMsgPack { ListRecord.Foo = Some "Hello"; Bar = [ 1 ] }

[rodrigovidal]

Hey @bhandfast, try to add the CLIMutable attribute to those records.

[<CLIMutable>]
type ListRecord = {
    Foo : string option;
    Bar: int list;
}

[bhandfast]

Thanks for the help. However, now I get another error.

System.Runtime.Serialization.SerializationException: Type 'Microsoft.FSharp.Collections.FSharpSet1[System.Int32]' does not have both of default (parameterless) public constructor and public constructor with an Int32 parameter. at MsgPack.Serialization.UnpackHelpers.GetCollectionConstructor(Type instanceType) at MsgPack.Serialization.AbstractSerializers.SerializerBuilder2.BuildCollectionCreateInstance(TContext context, Type concreteType)

Arrays seems fine though, guess I could remodel my type.

[yfakariya]

Sorry for delay. There are 2 problems.

1. There is a bug that record like type cannot be serialized if it has mutable collection type member.
2. As you know, FSharpSet<T> is not supported. You must register custom serializer for FSharpList, FSharpSet, and FSharpMap as built-in immutable collections support.

[yfakariya]

Fixed in 7bfdee5 for the bug. F# collection will not be supported in built-in serializers.