Lua Newcomer Observations

Today I wrote my first Neovim plugin with Lua. It replicates the “ag.vim” Silver Searcher Vim plugin that stopped working some time ago and it also has better auto-completion.

https://github.com/ncjones/dotfiles/blob/master/lvim/.lvim/lua/user/ag_command.lua

Lua is a dynamically typed, general-purpose programming language ideal for embedding in existing runtime environments for dynamic extension loading. Its syntax is intuitive and easy to learn and supports object-oriented programming. My initial observation was that it seemed like a simplified blend of JavaScript and Ruby. The Lua and Nvim standard libs are comically bare, though, so programmers often need to do additional work for common tasks like finding unique items in a collection.

The most striking gap in the Lua language is the lack of a common data structure abstraction. Lua’s foreach loop accepts an abstract iterator but, unlike Python, there’s no standard way to make something iterable. So, in order to iterate a data structure, you need to know how to create an iterator for it. From what I can tell, this is the biggest flaw in the language because it means interoperable code relating to data structures needs to be coupled with the native “table” data structure.

The Neovim Lua SDK fixes some of the gaps in the Lua standard library. Surprisingly, it doesn’t provide object-oriented solutions for interfacing with data structures like JavaScript, Ruby or Kotlin do. Instead of chaining collection methods like map, filter, find, and reduce, Lua devs need to nest calls to static utility functions. This results in a clunkier developer experience and code that’s harder to read. An example from my Ag plugin is the custom sorted set data structure abstraction. It needs to be converted back to a Lua table in order to use collection filtering.

The Neovim standard library also surprisingly lacks higher-level abstractions for dealing with files and buffers. I found that only low-level access was available for accessing file trees and buffer contents, so I needed to build my own abstractions.

Despite the quirks, I enjoyed writing Neovim plugins with Lua overall, and I expect to be back for more. Next time, I expect to be even more productive especially if I can get a proper TDD loop running.