Custom serializer/`JsonConverter` for a record

[rynoV]

Thanks for making this!

I didn't see this in the docs so I thought I'd mention it here: when registering a custom JsonConverter for a type in JsonFSharpTypes (e.g. records), it seems necessary to add it to the JsonSerializerOptions.Converters list before adding the json fsharp serializer options with AddToJsonSerializerOptions. Otherwise the fsharp record converter takes precedence.

Adding the JsonConverter directly to the record doesn't seem to take precedence. And it doesn't seem like using ToJsonSerializerOptions would work either.

[nkosi23]

Thanks, this has been very helpful to me.

[draganjovanovic1]

Hi @rynoV I am using custom JsonConverter attributes on some of my record and union types but serializer won't use them if I include JsonFSharpOptions in my JsonSerializerOptions.

I can't register all custom converters here in JsonSerializerOptions as I can't reference them and I don't like idea of adding them all in one place even if I could.

Any suggestion what to try? Thanks.

My options:

let options = JsonSerializerOptions ()
options.PropertyNamingPolicy <- JsonNamingPolicy.CamelCase
options.WriteIndented <- true
options.IndentSize <- 4
options.DefaultIgnoreCondition <- JsonIgnoreCondition.WhenWritingNull
options.NumberHandling <- JsonNumberHandling.AllowReadingFromString
options.Encoder <- JavaScriptEncoder.Default
options.Converters.Add (DateTimeConverterJsonConverter ())
options.Converters.Add (DateTimeOffsetConverterJsonConverter ())
options.Converters.Add (GuidJsonConverter ())
// with this part, my custom converter don't work, without it all good
let fsharpOptions =
    JsonFSharpOptions
        .Default()
        .WithIncludeRecordProperties()
        .WithUnionNamedFields()
        .WithSkippableOptionFields()
fsharpOptions.AddToJsonSerializerOptions (options)

[Tarmil]

@draganjovanovic1 If you use .WithAllowOverride() on your JsonFSharpOptions, then your custom converters will take priority.

[draganjovanovic1]

@Tarmil I tried adding . WithAllowOverride() as a last method in the fsharpOptions chain of the upper example but no luck.