Bucklescript bindings approaches for complex Object based arguments

TheAPIThatIWantToSupport.js

var CryptographyJs = require("./cryptography.js");

CryptographyJs.hash({ algorithm: 'md5', length: 10 }, "asd");
CryptographyJs.hash({ algorithm: 'md5' }, "asd");
CryptographyJs.hash({ length: 10 }, "asd");
CryptographyJs.hash({}, "asd");

TheAPIThatIWantToSupport.re

Cryptography.hashWithOpts(hashOptions(~algorithm=`MD5, ~length=10, ()), "asd");
Cryptography.hashWithOpts(hashOptions(~algorithm=`MD5, ()), "asd");
Cryptography.hashWithOpts(hashOptions(~length=10, ()), "asd");
Cryptography.hashWithOpts(hashOptions(), "111");

undefinedFieldsApproach.re

[@bs.deriving jsConverter]
type hash = [
  | [@bs.as "sha256"] `SHA256
  | [@bs.as "sha512"] `SHA512
  | [@bs.as "sha384"] `SHA384
  | [@bs.as "sha1"] `SHA1
  | [@bs.as "md5"] `MD5
];

[@bs.deriving abstract]
type hashConfig = {
  [@bs.optional]
  algorithm: string,
  [@bs.optional]
  length: int,
};

module Crypt_ = {
  [@bs.obj]
  external hashOptions :
    (~algorithm: Js.Nullable.t(string), ~length: Js.Nullable.t(int), unit) =>
    hashConfig =
    "";
};

let mapNullable = (opt: option('a), cb: 'a => 'b) =>
  switch (opt) {
  | Some(a) => Js.Nullable.return(cb(a))
  | None => Js.Nullable.undefined
  };

let hashOptions = (~algorithm=?, ~length=?, ()) =>
  Crypt_.hashOptions(
    ~algorithm=mapNullable(algorithm, hashToJs),
    ~length=mapNullable(length, i => i),
    (),
  );

[@bs.module "./cryptography.js"]
external hashWithOpts : (hashConfig, string) => unit = "hash";

hashWithOpts(hashOptions(~algorithm=`MD5, ~length=10, ()), "asd");

hashWithOpts(hashOptions(~algorithm=`MD5, ()), "asd");

hashWithOpts(hashOptions(~length=10, ()), "asd");

hashWithOpts(hashOptions(), "asd");

undefinedFieldsOutput.txt

{ algorithm: 'md5', length: 10 } 'asd'
{ algorithm: 'md5', length: undefined } 'asd'
{ algorithm: undefined, length: 10 } 'asd'
{ algorithm: undefined, length: undefined } 'asd'

UnsustainableApproach.re

[@bs.deriving jsConverter]
type hash = [
  | [@bs.as "sha256"] `SHA256
  | [@bs.as "sha512"] `SHA512
  | [@bs.as "sha384"] `SHA384
  | [@bs.as "sha1"] `SHA1
  | [@bs.as "md5"] `MD5
];

[@bs.deriving abstract]
type hashConfig = {
  [@bs.optional]
  algorithm: string,
  [@bs.optional]
  length: int,
};

module Crypt_ = {
  [@bs.obj]
  external hashOptions :
    (~algorithm: string=?, ~length: int=?, unit) => hashConfig =
    "";
};

let mapNullable = (opt: option('a), cb: 'a => 'b) =>
  switch (opt) {
  | Some(a) => Js.Nullable.return(cb(a))
  | None => Js.Nullable.undefined
  };

let hashOptions = (~algorithm=?, ~length=?, ()) =>
  switch (algorithm) {
  | Some(algorithm_) =>
    switch (length) {
    | Some(length_) =>
      Crypt_.hashOptions(
        ~algorithm=hashToJs(algorithm_),
        ~length=length_,
        (),
      )
    | None => Crypt_.hashOptions(~algorithm=hashToJs(algorithm_), ())
    }
  | None =>
    switch (length) {
    | Some(length_) => Crypt_.hashOptions(~length=length_, ())
    | None => Crypt_.hashOptions()
    }
  };

[@bs.module "./cryptography.js"]
external hashWithOpts : (hashConfig, string) => unit = "hash";

hashWithOpts(hashOptions(~algorithm=`MD5, ~length=10, ()), "asd");

hashWithOpts(hashOptions(~algorithm=`MD5, ()), "asd");

hashWithOpts(hashOptions(~length=10, ()), "asd");

hashWithOpts(hashOptions(), "asd");

UnsustainableOutput.txt

{ algorithm: 'md5', length: 10 } 'asd'
{ algorithm: 'md5' } 'asd'
{ length: 10 } 'asd'
{} 'asd'

A...nd got there. Honestly don't get how that wasn't obvious to me. facepalm

type hashConfig;

[@bs.obj]
external hashOptions :
  (~_Algorithm: string=?, ~length: int=?, unit) => hashConfig =
  "";

let hashOptions = (~algorithm=?, ~length=?, ()) =>
  hashOptions(
    ~_Algorithm=?Belt.Option.map(algorithm, hashToJs),
    ~length?,
    (),
  );

Cheers :D