Create test input for a Bytes decoder/encoder?

[KevinWMatthews]

Hi,

I’m doing my first experiments with elm and elm/bytes. I’m creating encoders/decoders and looking for an easy way to give them input data while I’m learning and testing.

Decoders (and a Bytes encoder) accept a Bytes type, but this type seems to be (justifiably) opaque. Is there a way to create a Bytes type directly? Is there another approach to experimenting with encoders/decoders?

For example, if I’m naively encoding an Int:

type alias IntThing =
    { -- more fields later
      data : Int
    }

toIntThingEncoder : IntThing -> Encoder
toIntThingEncoder thing =
    Encode.unsignedInt8 thing.data

I can easily experiment with it using something like:

toIntThingEncoder { data = 3 }

If, however, if I’m using a Bytes type:

type alias ByteThing =
    { -- more fields later
      data : Bytes
    }


toByteThingEncoder : ByteThing -> Encoder
toByteThingEncoder thing =
    Encode.bytes thing.data

I’m not sure of an easy way to get data to feed into the encoder:

encode (toByteThingEncoder ?)

Any insight would be much appreciated.

Thanks!

[dmy]

I’m not sure to understand what you mean.
The way to create Bytes is to use Bytes.Encode.encode, as you know, so you can do:

encode (toByteThingEncoder {data = encode (Encode.unsignedInt8 3)} )

or using any other Encode function which produces an Encoder. You could use for example sequence with a list of unsigned byte values like

{ data = encode <| Encode.sequence <| List.map Encode.unsignedInt8 [0x42, 0xff, ... ] }

You would most likely need a way to also encode the width though.

[KevinWMatthews]

Ah, you’re right! I didn’t think to use a Bytes.Encode.encode.

Thank you for showing the example with List.map! That was a missing piece, and I think it would’ve taken me a long time to figure that out.