Promise Async Save
Promise & Async in Lua
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
- 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
Script
demo.lua
demo.js
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'}
or
- As a Luarocks plugin
use_rocks {'promise-async'}
As a library from Luarocks
-
luarocks install promise-async -
luarocks install luvor 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 ofAsync.waitfunction; -
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 tovim.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.
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