In a team environment, where the way event contracts are composed is often a matter of debate, it can be useful to have a way to validate that types that will be mapped to JSON adhere to conventions.
It should be pretty possible to, a la AutoFixture.Idioms use reflection to find all DUs that implement TypeShape.UnionEncoder.IUnionContract, and then walk the type with TypeShape counting anomalies such as
- using
FSharpList without a converter (use array or [] option)
- using tuples anywhere in a union contract (a converter, e.g. based on a JsonIsomorphism should be permitted, but we definitely don't want random Newtonsoft/STJ representations and/or runtime exceptions)
- Using
DateTime (DateTimeOffset is hands down better)
- Using Enums (use nullary unions / TypeSafeEnums in preference)
- using SCDUs without a converter (should probably be using UMX in the data contracts and only using SCDUs where warranted in models)
- using other unions without tagging the type and/or field with a converter (e.g. UnionConverter) (vs ending up e.g. triggering Newtonsofts built-in encoding)
- using anything that binds to a name
Item* (e.g. unions with single item or tuple bodies)
This would enable a team for write a single unit test saying something like:
let [<Fact>] ``All contract types use simple tagged types`` () =
let checker = FsCodec.NewtonsoftJson.TypeChecker(allowMaps=true) // or any other exceptions to the search
let anoms =
TypesImplementing<TypeShape.UnionEncoder.IUnionContract>(typeof<Domain.SampleType>.Assembly)
|> Seq.collect checker.EnumViolations
|> List.ofSeq
test <@ [] = anoms @>
Reasons to have this in FsCodec vs anywhere else
- it's already using TypeShape
- we can port it to do the same thing for SystemTextJson
Yes, one could build a Roslyn Analyzer and/or Rider or Ionide checks too!
In a team environment, where the way event contracts are composed is often a matter of debate, it can be useful to have a way to validate that types that will be mapped to JSON adhere to conventions.
It should be pretty possible to, a la
AutoFixture.Idiomsuse reflection to find all DUs that implementTypeShape.UnionEncoder.IUnionContract, and then walk the type with TypeShape counting anomalies such asFSharpListwithout a converter (usearrayor[] option)DateTime(DateTimeOffsetis hands down better)Item*(e.g. unions with single item or tuple bodies)This would enable a team for write a single unit test saying something like:
Reasons to have this in FsCodec vs anywhere else
Yes, one could build a Roslyn Analyzer and/or Rider or Ionide checks too!