Convert decode.field to decode.optional_field code action

[folospior]

The Generate dynamic decoder code action is great, but one thing that I feel it's been lacking at is optionals.

Currently, this type:

pub type Wibble {
  Wibble(wobble: Option(Int))
}

will have this decoder generated:

fn wibble_decoder() -> decode.Decoder(Wibble) {
  use wobble <- decode.field("wobble", decode.optional(decode.int))
  decode.success(Wibble(wobble:))
}

However, Options can be used to represent two states (JSON examples):

• the absence of a field:

{}

• or the field is null:

{"wobble": null}

The decoder above will fail in case it can't find the wobble field. Because of that, the code decoding the field has to be changed, such that it uses decode.optional_field:

fn wibble_decoder() -> decode.Decoder(Wibble) {
  use wobble <- decode.optional_field(
    "wobble",
    None,
    decode.optional(decode.int),
  )
  decode.success(Wibble(wobble:))
}

How I've been personally dealing with this issue is via macros. There a few issues associated with that, compared to a code action:

• One has to make multiple macros for the different ways of formatting decoders (one-line or multi-line)
• Macros aren't available in every editor (such as VS Code)

What I suggest to mitigate this is a code action, Convert to optional_field, which, when ran, will convert the code from the first example into the code from the second example.

fn wibble_decoder() -> decode.Decoder(Wibble) {
  // Highlighted here - convert to optional_field
  //                   vvvvv
  use wobble <- decode.field("wobble", decode.optional(decode.int))
  decode.success(Wibble(wobble:))
}

[lpil]

Hello! Please use discussions for proposals, issues are for actionable work and bugs.

[lpil]

Looks like this is a duplicate: #5082