Awesome

promise-async

The goal of promise-async is to port Promise & Async from JavaScript to Lua.

A value returned by async function in JavaScript is actually a Promise Object. It's incomplete and inflexible for using an async function wrapped by bare coroutine without Promise in almost Lua implementation.

Features
Demonstration
- Script
  - demo.lua
  - demo.js
Quickstart
- Requirements
- Installation
  - As a plugin for Neovim platform
  - As a library from Luarocks
Documentation
- Summary
- async
Development
Credit
Feedback
License

Features

API is similar to JavaScript's
Customize EventLoop in any platforms
Support Lua 5.1-5.4 and LuaJIT with an EventLoop module
Support Neovim platform

Demonstration

https://user-images.githubusercontent.com/17562139/169118448-9468909b-dbde-4dde-9308-ffe71abb24cd.mp4

Script

demo.lua

https://github.com/kevinhwang91/promise-async/blob/3f6dcb2f0f546e8be7e170785f07f71ef6afab34/examples/demo.lua#L17-L82

demo.js

https://github.com/kevinhwang91/promise-async/blob/3f6dcb2f0f546e8be7e170785f07f71ef6afab34/examples/demo.js#L1-L58

Quickstart

Requirements

Lua 5.1 or latter
Luv

Luv is a default EventLoop for promise-async. It doesn't mean promise-async must require it. In fact, promise-async require a general EventLoop module which Luv like.

Installation

As a plugin for Neovim platform

Install with Packer.nvim:

As a normal plugin

use {'kevinhwang91/promise-async'}

As a Luarocks plugin

use_rocks {'promise-async'}

As a library from Luarocks

luarocks install promise-async
luarocks install luv or implement an EventLoop interface to adapt your platform

Documentation

promise-async's API is based on MDN-Promise. typings/promise.lua is the typings with documentation of Promise class.

Summary

Summary up the API different from JavaScript.

JavaScript	Lua
`new Promise`	`Promise:new`/`Promise`
`Promise.then`	`Promise:thenCall`, `then` is language keyword
`Promise.catch`	`Promise:catch`
`Promise.finally`	`Promise:finally`
`Promise.resolve`	`Promise.resolve`
`Promise.reject`	`Promise.reject`
`Promise.all`: `Symbol.iterator` as iterator	`Promise.all`: `pairs` as iterator
`Promise.allSettled`: `Symbol.iterator` as iterator	`Promise.allSettled`: `pairs` as iterator
`Promise.any`: `Symbol.iterator` as iterator	`Promise.any`: `pairs` as iterator
`Promise.race`: `Symbol.iterator` as iterator	`Promise.race`: `pairs` as iterator
`async`: as keyword at the start of a function	`Async`/`Async.sync`: as a surrounding function
`await`: as keyword	`await`/`Async.wait` as a function

async

The environment in Async.sync function have been injected some new functions for compatibility or enhancement:

await: A reference of Async.wait function;
pcall: Be compatible with LuaJIT;
xpcall: Be compatible with LuaJIT;

async in JavaScript return Promise object only with single result, but may carry multiple results in Lua. The resolved result of Promise object return by async function will be packed into a table via {...}. However, the result handled by await will be unpacked and return multiple values.

local async = require('async')

local function f()
    return 1, 2, 3
end

-- multiple results are packed into resolved result in Promise
async(f):thenCall(function(v)
    print(v[1], v[2], v[3]) -- output: 1 2 3
end)

-- results returned by `await`
async(function()
    local v1, v2, v3 = await(async(f))
    print(v1, v2, v3) -- output: 1 2 3
end)

uv.run()

Development

Neovim tips

Promise.resolve():thenCall(cb) is almost equivalent to vim.schedule(cb).

Run tests

make test

Improve completion experience

Following typings/README.md

Customize EventLoop

TODO, refer to loop.lua

Credit

Feedback

If you get an issue or come up with an awesome idea, don't hesitate to open an issue in github.
If you think this plugin is useful or cool, consider rewarding it a star.

License

The project is licensed under a BSD-3-clause license. See LICENSE file for details.