Elixir: Open Files with Vim using IEx.Helpers.open/1

One of the less known (but useful) features of Elixir’s IEx module is the open/1 function. Open works with either a given Module, Module.function/arity or {file, line_number}. Once configured, it allows the developers to open a file with a given file path and line number. This is incredibly useful while debugging inside a IEx.pry session as it allows you to jump to the place where a particular function is defined.

For example:

iex> open String.to_atom/1

Calling open as above will open the file corresponding to the String module where to_atom is defined.

To accomplish this IEx.Helpers module uses the environment variable, ELIXIR_EDITOR. If the environment variable isn’t exported, it uses EDITOR as a fallback.

However, by default it attempts to open the editor while keeping the iex session alive. So, this command doesn’t work with vim or nvim right off the bat.

Configuring open/1 to work with Vim (and Neovim)

I will be configuring open/1 to work with nvim (my primary text editor). But, a similar configuration can be used for vim and other terminal-based editors.

Let’s start by adding exporting the ELIXIR_EDITOR environment variable.

# in ~/.bashrc (or ~/.zshrc)

export ELIXIR_EDITOR="nvim"

But this won’t work. In order for open/1 to work with nvim, we need to satisfy two cases:

• open/1 should attempt to open nvim in a separate window. This will keep the IEx session alive while giving us the ability to open a file.
• open/1 attempts to open a file using file:line notation, which doesn’t work with nvim. So, we will have to configure the format of that notation.

For the first case, we can just open our nvim in a new terminal as follows:

Linux Users (with gnome-terminal)

# in ~/.bashrc (or ~/.zshrc)

export ELIXIR_EDITOR="gnome-terminal -- nvim"

Mac Users

# in ~/.bashrc (or ~/.zshrc)

export ELIXIR_EDITOR="open -a Terminal 'nvim'"

This should allow us to call open, but we still have to configure the editor command to take a line_number. Elixir provides interpolation for __FILE__ and __LINE__.

We can use them to open a file with a specific line_number in a Neovim window as follows:

Linux Users (with gnome-terminal)

# in ~/.bashrc (or ~/.zshrc)

export ELIXIR_EDITOR="gnome-terminal -- nvim +__LINE__ __FILE__"

Mac Users

# in ~/.bashrc (or ~/.zshrc)

export ELIXIR_EDITOR="open -a Terminal 'nvim +__LINE__ __FILE__'"

Now running and iex and calling open/1 should open a file with a specific line number.

With Tmux

Since I use tmux, I changed my final version of the ELIXIR_EDITOR env to look like this:

Linux Users (with gnome-terminal)

# in ~/.bashrc (or ~/.zshrc)

export ELIXIR_EDITOR="gnome-terminal tmux new -- nvim +__LINE__ __FILE__"

Mac Users

# in ~/.bashrc (or ~/.zshrc)

export ELIXIR_EDITOR="open -a Terminal 'tmux new nvim +__LINE__ __FILE__'"

This allows me to open a file in nvim with tmux configurations.

Here is the finished product:

File-Jump Heaven

This also works with open/0 which opens the current prying location inside a prying session started by either calling IEx.pry/0 or IEx.break!/4.

Check out IEx.Helpers.open/1 for more information.