🚂 Steamroller

Steamroller is an opinionated Erlang code formatter. Uniformity is inevitable.

Upset your colleagues by autoformatting their code.

This rebar3 plugin is early stage but could be used in production if you're brave. The Erlang abstract syntax tree is checked before and after formatting to make sure that the formatted file is equivalent to the original.

Steamroller should be used as part of your CI to enforce a consistent style across your codebase.

Use

Add steamroller to your rebar config:

{plugins, [steamroller]}.

Then ask it to steamroll your code directly in an existing application:

$ rebar3 steamroll
===> Fetching steamroller
===> Compiling steamroller
<Steamroller Output>

Editor Integration

Vim

You can use steamroller from vim with [Neoformat][https://github.com/sbdchd/neoformat].

Install Neoformat and then paste the below into your vimrc.

" Erlang autoformat
let g:neoformat_erlang_steamroller = {
  \ 'exe': 'rebar3',
  \ 'args': ['steamroll -f'],
  \ 'stdin': 0,
  \ 'replace': 1,
  \ }
let g:neoformat_enabled_erlang = ['steamroller']
autocmd BufWritePre rebar.config,*.[he]rl,*.app.src Neoformat steamroller

CI

To check that code is properly formatted as part of your CI:

$ rebar3 steamroll --check

The exit code will be non-zero if the code has not been formatted before being committed.

Build

$ rebar3 compile

Test

$ rebar3 test

Dialyzer

Dialyzer is Erlang's static analysis tool.

$ rebar3 dialyzer

Local Development

In order to use steamroller locally on itself you need to symlink the repo into the _checkouts directory:

cd $local_steamroller_repo
mkdir _checkouts
ln -s $PWD ./_checkouts/steamroller

Rebar3 will use the version of steamroller in the _checkouts directory with higher priority than the version specified in the rebar.config. There's a line in the rebar.config (see overrides) which prevents infinite plugin loops when using steamroller locally like this.