This week GitHub user vlaci called us out on awful F# support in Serilog. In their issue report they show how a nice clean discriminated union type like “Option” is represented hideously in structured data:

type Shape =
    | Circle of Radius : double
    | Rectangle of Width : double *  Height : double
    | Arc // ...
let shape = Circle 5.
Log.Information("Drawing a [email protected]}", shape)


2015-01-14 16:52:06 [Information] Drawing a Circle { Radius: 5, Tag: 0, IsCircle:
   True, IsRectangle: False, IsArc: False }

The verbosity gets worse for types with more values.

I took this as a chance to crank up Visual Studio and get reacquainted with F#, using the example from @vlaci as a starting point. Using Serilog.Extras.FSharp you can now enjoy your discriminated unions encoded pleasantly like:

2015-01-14 16:58:31 [Information] Drawing a Circle { Radius: 5 }

Depending on the log storage you use you’ll be able to query on the tag as well as the fields (like Radius) from the union.

You can enable this by installing the package and adding Destructure.FSharpTypes() to your logger configuration:

open Serilog

let main argv = 

    Log.Logger <- LoggerConfiguration()

    Log.Information("Drawing a [email protected]}", Circle 5.)


Thanks again to vlaci for kicking this off. I was especially keen to see this in because I’m sure someone with better F# skills than mine can add a lot to the Serilog/F# experience. If you have ideas we’d love to hear from you on the project site!