[REQ][Elm] Remove DateTime in favour of Posix

[andys8]

Is your feature request related to a problem? Please describe.

Generated code is obfuscating Posix with a new name DateTime.

Describe the solution you'd like

DateTime is an alias for Time.Posix. Since Time.Posix is now being used everywhere in Elm applications, it could make sense to remove the type alias for clarification. I think this is a left-over from the code base before Time.Posix was introduced.

[wing328]

@andys8 thanks for the suggestion.

cc @eriktim

[wing328]

What about using --type-mapping with Time.Posix for the time being?

[andys8]

@wing328 Could work, but isn't really necessary. Because it's a type alias it can be used the same way without the need to convert it.

The suggestion is mainly targetted towards avoiding confusion and using the type people know.

Thanks for the tipp.

[eriktim]

I could rename the alias to Posix. That indeed makes sense. We can still use the decoder/encoder then. Any suggestions what to do with the DateOnly version then? Alias it as PosixDate? I do like the fact the type (alias) keeps them distinct.

[andys8]

I was thinking of dropping the name. Is anything wrong with it or would you subject doing it like this?

module DateTime exposing (decoder, encode, toString)

import Iso8601
import Json.Decode as Decode exposing (Decoder)
import Json.Encode as Encode
import Result
import Time exposing (Posix)


decoder : Decoder Posix
decoder =
    Decode.string
        |> Decode.andThen decodeIsoString


encode : Posix -> Encode.Value
encode =
    Encode.string << toString


decodeIsoString : String -> Decoder Posix
decodeIsoString str =
    case Iso8601.toTime str of
        Result.Ok posix ->
            Decode.succeed posix

        Result.Err _ ->
            Decode.fail <| "Invalid date: " ++ str


toString : Posix -> String
toString =
    Iso8601.fromTime

[eriktim]

There are two issues here:

• To be honest I do not know how easy it would be to have the type (Posix) come from a different module than the de/encoders (DateTime) in the generator;
• There is also DateOnly. I would like the record to have distinct types for dates with time and dates without time.

[eriktim]

In the upcoming 5.0.0 release both date and date-time are now Posix values. Be aware that in case of date not the exact Posix value gets transmitted as the time is stripped off.