Alex alex35mil

Prefer Sum Types Over Strings and Booleans

Design domain types to make illegal states unrepresentable. Use enums/variants (sum types) instead of strings or booleans when a value has a fixed set of meaningful states.

Strings Allow Invalid Values

// ❌ WRONG: Any string is accepted, typos compile fine
struct Post {
    status: String, // "draft", "published", "archived"... or "publsihed"?
}

Promise.res

A slightly modified version of standard ReScript's Js.Promise module.

Key differences are:

t-first api
contains few helpers like Promise.result and Promise.wait (which is what I want most of the time in apps)

Soundness is on the same level as in the original bindings.

If you want more safety, consider reason-promise.

Install these packages:

yarn install --dev @babel/core @babel/preset-env jest babel-jest

Add babel.config.js (exactly babel.config.js, not .babelrc, not .babelrc.json etc):

module.exports = {

	// Hybrid Logical Clocks implementation in Rust.
	// Based on:
	// - https://cse.buffalo.edu/tech-reports/2014-04.pdf
	// - https://github.com/jlongster/crdt-example-app/blob/master/shared/timestamp.js
	// - https://github.com/jaredly/hybrid-logical-clocks-example/blob/master/src/hlc.js

	use std::{
	char, cmp, fmt, num, ops, str,
	time::{Duration, SystemTime, UNIX_EPOCH},
	};

	type transitionHook = Dom.htmlElement => unit;

	module type Css = {
	let duration: int;
	let appear: string;
	let enter: string;
	let exit: string;
	let appearActive: string;
	let enterActive: string;
	let exitActive: string;

	open Belt;

	type t(+'a) = Js.Promise.t('a);
	type error = Js.Promise.error;

	type result('ok, 'error) = t(Result.t('ok, 'error));

	[@bs.new]
	external make:
	(

	module Lifetime = {
	type t =
	\| Months(int)
	\| Days(int)
	\| Hours(int)
	\| Minutes(int)
	\| Seconds(int)
	\| Session
	\| Short;

	open Belt;

	type t(+'a) = Js.Promise.t('a);
	type error = Js.Promise.error;

	type result('ok, 'error) = t(Result.t('ok, 'error));

	external errorToString: error => string = "%identity";

	[@bs.new]

	module Modifier = {
	type t =
	\| Date(Js.Date.t)
	\| Range(Js.Date.t, Js.Date.t)
	\| Fn(Js.Date.t => bool);

	let toJs =
	(. x) =>
	switch (x) {
	\| Date(date) => date

	<TextField
	icon=(module IconOk)
	value
	onChange=change
	/>