DevotionGeo

DevotionGeo

Formatting your Erlang code in Visual Studio Code

There are 3 main formatters for Erlang which you can use from the command-line,

Visual Studio Code’s extension called Erlang Formatter uses these formatters to format Erlang code on save or when the shortcut keys combination is pressed which is Shift + Alt + F on Windows, Shift + Option + F on Mac and Ctrl + Shift + I on Linux.
(Note: the erlang extension also tries to format Erlang code, but it wasn’t working for me, and it doesn’t have any setting to set the desired formatter).

Following were the steps I used to make it work (all the settings and instructions can be found at Github READMEs of Erlang Formatter for VSCode and rebar3_format, and the Getting Started Page of rebar3, but I’m trying to make it a tiny bit less confusing than how I found it).

  1. Install rebar3:
    If you already have Elixir installed, chances are that there is a rebar3 binary somewhere in that installation. Mine was at ~/.asdf/installs/elixir/1.10.4-otp-23/.mix/rebar3 as I use asdf for version management. In that case you can run the following command, replacing the path with the path to rebar3 on your machine, or can go to the directory where rebar3 is located and run as ./rebar3.
    -> ~/.asdf/installs/elixir/1.10.4-otp-23/.mix/rebar3 local install

    Then add export PATH=$PATH:~/.cache/rebar3/bin to your .bashrc or .zshrc. And after that run the second command as,
    -> rebar3 local upgrade
    (this time you don’t need to add ./ or the complete path to the command, as rebar3 (the new copy) is already installed to ~/.cache/rebar3/lib and is added to the path).

    Alternatively you can run the following commands to install from source.
    -> git clone https://github.com/erlang/rebar3.git
    -> cd rebar3
    -> ./bootstrap
    -> ./rebar3 local install
    Don’t forget to add export PATH=$PATH:~/.cache/rebar3/bin to your .bashrc or .zshrc.

  2. Create a rebar.config file under ~/config/rebar3/ or simply run the following comand in the terminal.
    -> code ~/.config/rebar3/rebar.config
    which will open a rebar.config file under ~/.config/rebar3/ in vscode.
    Add the format configuration to this file. You can find the configuration options at the rebar3_format README at Github.
    Following is my rebar.config (notice the comments).

{plugins, [rebar3_format]}.
{format, [
    {files, ["**/*.erl"]},
    {formatter, default_formatter},
    {options, #{
        % paper => 100,
        % inline_qualified_function_composition => true,
        % inline_simple_funs => true,
        % inline_items => all,
        % inline_attributes => all,
        % inline_expressions => true,
        inline_clause_bodies => true
    }}
]}.
  1. Install the VSCode extension Erlang Formatter, if not installed already, and add the following settings to your settings.json.
  "[erlang]": {
    "editor.tabSize": 4,
    "editor.defaultFormatter": "szTheory.erlang-formatter",
    "editor.formatOnSave": true
  },
  "erlangFormatter.formatter": "rebar3_format",

I wanted to have a 2 spaces tab size for Erlang, but looks like it’s a setting of rebar3_format which can’t be overridden, so I set it to 4 spaces in the editor too, so that the indent guides don’t look off.

Edit: There is a setting break_indent, which can be used to have 2 space indents instead of 4.

(Note: feel free to edit this post).

Most Liked

AstonJ

AstonJ

Nice one - thanks for writing this up DG! :+1:

I’ve made it a wiki for you too - if anyone edits it you’ll be sent a notification :nerd_face:

DevotionGeo

DevotionGeo

You’re welcome and thank you! :slight_smile:

DevotionGeo

DevotionGeo

I changed the Erlang formatter from rebar3_format to erlfmt and it proved to be a lot better than rebar3_format.
The rebar.config contains only one line now, which is {plugins, [erlfmt]}.

Where Next?

Popular Backend topics Top

dimitarvp
Apparently he decided to live-stream how he’s going to create a semver library.
New
First poster: bot
In a previous post we talked about implementing a simple video chat with WebRTC and Elixir. This update will touch on some of the API cha...
New
First poster: malloryerik
Everyone outside of tech has heard of JavaScript, Java, Python, Ruby and even .Net, but few if any have heard of F#. However, F# may be o...
New
paulanthonywilson
Following up on the previous post on using UDP multicasting to broadcast and detect peers on a network, I create a registry of those peer...
New
First poster: bot
Ruby on Rails is a web framework that contains many libraries you’d need to create and deploy a successful web application. We often take...
New
First poster: bot
At Grammarly, the foundation of our business, our core grammar engine, is written in Common Lisp. It currently processes more than a thou...
New
wolf4earth
Louis Pilfold is the creator of the Gleam programming language. He explains what Gleam is and tells us where it came from. He then dives...
New
tonyxrandall
As DoorDash transitioned from Python monolith to Kotlin microservices, our engineering team was presented with a lot of opportunities to ...
New
StuntProgrammer
In building lofi.limo, media storage and distribution naturally came up. I have songs, announcements, and background image loops which I ...
New
fullstackplus
The Ruby ecosystem is rich with tools that make us developers more productive at what we do. Both Rails and Sinatra have been used to bui...
New

Other popular topics Top

ohm
Which, if any, games do you play? On what platform? I just bought (and completed) Minecraft Dungeons for my Nintendo Switch. Other than ...
New
siddhant3030
I’m thinking of buying a monitor that I can rotate to use as a vertical monitor? Also, I want to know if someone is using it for program...
New
Exadra37
Oh just spent so much time on this to discover now that RancherOS is in end of life but Rancher is refusing to mark the Github repo as su...
New
AstonJ
If you are experiencing Rails console using 100% CPU on your dev machine, then updating your development and test gems might fix the issu...
New
AstonJ
Saw this on TikTok of all places! :lol: Anyone heard of them before? Lite:
New
Maartz
Hi folks, I don’t know if I saw this here but, here’s a new programming language, called Roc Reminds me a bit of Elm and thus Haskell. ...
New
New
PragmaticBookshelf
Programming Ruby is the most complete book on Ruby, covering both the language itself and the standard library as well as commonly used t...
New
PragmaticBookshelf
Author Spotlight: Peter Ullrich @PJUllrich Data is at the core of every business, but it is useless if nobody can access and analyze ...
New
PragmaticBookshelf
Fight complexity and reclaim the original spirit of agility by learning to simplify how you develop software. The result: a more humane a...
New