Elixir Style: Prefer Unnested Aliases

This post was originally written for my old ElixirFocus blog, and transfer here after its closure.

In Elixir, alias is a keyword we often use to create shorthand references to long-form module names allowing us to refer to RetroTaxi.Boards.Board simply as Board.

You’ll often end up with a collection of alias declarations at the top of a module, and Elixir offers two ways to format these.

One way is simple list such as:

alias RetroTaxi.Boards.Board
alias RetroTaxi.Boards.Column
alias RetroTaxi.Boards.TopicCard

The other way is an optional nested list like:

alias RetroTaxi.Boards.{Board, Column, TopicCard}

Sometimes this nested list is broken across separate lines and presented like:

alias RetroTaxi.Boards.{
    Board,
    Column,
    TopicCard
}

Style Recommendation

I highly recommend avoiding this nested presentation. The primary reason is to help keep the codebase plain-text searchable. By avoiding the nesting, you can quickly find which modules are referencing any module simply by searching for its name string like RetroTaxi.Boards.Column. Finding nested aliases would require a more complex regular expression or language server tooling.

If you want to enforce this style with a credo, check out Credo.Check.Readability.MultiAlias which is usually disabled on a default credo install.

About the Author. Mike Zornek is a developer and teacher focusing on product design and development with a heavy focus on Elixir and LiveView. In between his projects, Mike helps other teams through consulting. During off hours, he enjoyed watching Phillies baseball and playing relaxing video games.

Hopefully, you found interest in my scribbles. If you have commentary or a response, I'd love to hear it.