Mavnn's blog

Stuff from my brain

We're running Building Solid Systems in F# in London, 31 Jan - 1 Feb 2018. High quality training for building .NET Core, F#, distributed production ready systems.

Type Provider ProTip

While type providers are incredibly powerful, the ProvidedTypes api for creating them is sometimes a bit rough around the edges. And not always as functional as you might hope.

At some point I'd like to do something about that, but for the moment I'm just going to collect a few helpful tips and hints (mostly for own reference).

Tip one is in the case where you have XmlDocs to add to ProvidedTypes, ProvidedMethods and ProvidedProperties; in our case we have an optional description field in our metadata and the boiler plate was getting tiresome.

let inline addDoc (desc : Descriptor) def =
    match desc.Description with
    | Some d ->
        (^T : (member AddXmlDoc : string -> unit) (def, d))
    | None -> ()

This function takes a Descriptor with a string option Description field and any def with an AddXmlDoc member with the noted signature - and adds description as the xml doc if it exists.