Over the last week I’ve been learning some Rust in my spare time and saw that they have a convention of storing the top level module for a namespace in a file called mod.rs. In Elixir this would look like this:

├── foo
│   └── bar.ex
│   └── mod.ex

Compared to the Elixir convention of doing this:

├── foo
│   └── bar.ex
└── foo.ex

I thought there were advantages and disadvantages to each approach. The Rust structure groups the top level module together with it’s child modules, but the name mod.ex is a bit ambiguous, and doesn’t immediately stand out from the child modules. The advantage of the Elixir way is that the file structure matches the module namespace.

I’m suggesting this way of doing it:

├── foo
│   └── _foo.ex
│   └── bar.ex

Here a leading underscore is used to indicate the top level module. This means that when you open a folder the first file is the top level module. The file name also includes the module name, which I find convenient (I know at a glance which mod.ex file I am working with).

I talked to the guys at work and they liked the idea. What does the community think? If it’s unpopular we might use it internally, or we might drop the idea if there is a good reason not to do it.