Styler is an Elixir formatter plugin that's combination of mix format and mix credo, except instead of telling you what's wrong, it just rewrites the code for you to fit its style rules.

Add :styler as a dependency to your project's mix.exs:

def deps do
  [
    {:styler, "~> 0.5", only: [:dev, :test], runtime: false},
  ]
end

Add Styler as a plugin to your .formatter.exs file

[
  plugins: [Styler]
]

And that's it! Now when you run mix format you'll also get the benefits of Styler's definitely-always-right style fixes.

We recommend using Styler as a plugin, but it comes with a task for other use cases as well.

$ mix style

The task can helpful for slowly converting a codebase directory-by-directory. It also allows you to use mix archive.install to easily test run Styler on a project without modifying its dependencies:

$ mix archive.install hex styler

mix style is designed to take the same basic options as mix format.

See mix help style for more.

There isn't any! This is intentional.

Styler's @adobe's internal Style Guide Enforcer - allowing exceptions to the styles goes against that ethos. Happily, it's open source and thus yours to do with as you will =)

Expect the first run to take some time as Styler rewrites violations of styles. Afterwards, it shouldn't take much longer than a normal mix format.

Additionally, two sad situations may happen on your first run:

• module compilation breaks if a reference to an alias is moved to be before the alias's declaration (part of the StrictModuleLayout credo rule)
  • there's nothing for it but to manually fix things, typically by writing out the entire module name where it's referenced before its alias
• comments get put weird places
  • sorry! only our def-shortening style is currently aware of comments. that means that they can get a little out of sorts when other rules move things around.
  • manually put them back where you want them, and they shouldn't be moved again
  • feel free to open or 1 an issue in the hopes that we get around to handling this

You can find the currently-enabled styles in the Styler module, inside of its @styles module attribute. Each Style's moduledoc will tell you more about what it rewrites.

The best place to get an idea of what sorts of changes Styler makes is by looking at the tests for each Style.

Someday we'll announce Styler to the world, and hopefully by then we have some examples written into this here README :)

If you're using Credo and Styler, we recommend disabling these rules in .credo.exs to save on unnecessary checks in CI.

This work was inspired by earlier large-scale rewrites of an internal codebase that used the fantastic tool Sourceror.

The initial implementation of Styler used Sourceror, but Sourceror's AST-embedding comment algorithm slows Styler down to the point that it's no longer an appropriate drop-in for mix format.

Still, we're grateful for the inspiration Sourceror provided and the changes to the Elixir AST APIs that it drove.

The AST-Zipper implementation in this project was forked from Sourceror's implementation.

Similarly, this project originated from one-off scripts doing large scale rewrites of an enormous codebase as part of an effort to enable particular Credo rules for that codebase. Credo's tests and implementations were referenced for implementing Styles that took the work the rest of the way. Thanks to Credo & the Elixir community at large for coalescing around many of these Elixir style credos.