nd (nix develop)

POC for an easy and fast nix develop workflow that works well with tmux.

usage

• nd build or nd b will build a devShell.
• nd shell or nd s or nd will start a devShell.
• nd run something or nd r something will run something inside a devShell.

By default it looks for any flake in the current folder or a parent folder, and it uses the default shell (#default).

All of the above commands can also be started with nd at flakeref ... to use a different flake. For example nd at ~/fun/project run cargo --version will use that devShell even when you are in a different folder. Only local flake references are allowed:

• ../somewhere/here
• ../somewhere/here#name
• path:../somewhere/here

Additionally, the flake reference - is allowed. It means no flake, and nd run something runs something normally, without a devShell.

Alternatively, if there is an env var nd_env, then you can also use nd env ... or nd e ... to use the flake reference pointed at by nd_env. This is mostly useful for tmux, see below. nd env run something just runs something normally, if there is no nd_env.

The cached devShell is in .nd. You have to explicitely rebuild. It will only build automatically if there is no cached devShell yet. The cached devShell's .nd will always be at the referenced flake's location, which is not necessarily your project's root.

Remember that a flake's shellHook is run in the current directory, and not necessarily in the project root, and therefore something like export PATH=$PWD/bin:$PATH is not very robust.

tmux

Set the default-shell of tmux to tmux-nd-shell. In tmux.conf:

run-shell -b 'tmux set-option -g default-shell `which tmux-nd-shell`'

Then run a tmux session with the env var nd_env set to the project's flake reference. Every shell inside that tmux session will now be a devShell.

tmux new-session -e nd_env=$HOME/fun/project

Note that you cannot use ~ here, it won't be expanded. That is zsh behaviour, not nd behaviour.

Or use nd tmux to start an nd-enabled session. Note that the session's folder will be the current folder, but the session's nd flake can be from a different place when using nd at ~/other/place tmux.

If you have things you run on shortcuts within tmux, and if they should (sometimes) use nd, a convenient way is to map it to nd env run something. It will work no matter if nd_env is set or not.

tmux bind-key g run-shell -b 'nd env run something --arg value'