json 🐑

Work with JSON in Glistix!

This is a fork of gleam_json which adds support for Glistix’s Nix target.

Incompatibilities

Please note that, currently, JSON decoding (the decode function) will crash when receiving invalid JSON input on the Nix target instead of gracefully failing and returning an Error.

This is because it uses builtins.fromJSON which aborts execution on invalid input. A fix for this while retaining efficiency would likely depend on changes to Nix itself.

Installation

You can use this fork by running glistix add gleam_json followed by adding the line below to your Glistix project’s gleam.toml file (as of Glistix v0.7.0):

[glistix.preview.patch]
# ... Existing patches ...
# Add this line:
gleam_json = { name = "glistix_json", version = ">= 1.0.0 and < 2.0.0" }

This ensures transitive dependencies on gleam_json will also use the patch.

For the most recent instructions, please see the Glistix handbook.

Encoding

import myapp.{Cat}
import gleam/json.{object, string, array, int, null}

pub fn cat_to_json(cat: Cat) -> String {
  object([
    #("name", string(cat.name)),
    #("lives", int(cat.lives)),
    #("flaws", null()),
    #("nicknames", array(cat.nicknames, of: string)),
  ])
  |> json.to_string
}

Decoding

JSON is decoded into a Dynamic value which can be decoded using the gleam/dynamic module from the Gleam standard library.

On the Nix target, invalid JSON input will cause a crash instead of returning an Error. Ensure you always provide valid JSON input.

import myapp.{Cat}
import gleam/json
import gleam/dynamic.{field, list, int, string}

pub fn cat_from_json(json_string: String) -> Result(Cat, json.DecodeError) {
  let cat_decoder = dynamic.decode3(
    Cat,
    field("name", of: string),
    field("lives", of: int),
    field("nicknames", of: list(string)),
  )

  json.decode(from: json_string, using: cat_decoder)
}