Add direnv

[levydsa]

Add use flake configuration for direnv. For Nix users, being able to hop into a directory and loading the environment automatically is very convenient.

[thisismiller]

Committing this sort of locks out anyone from doing anything else with direnv though (which layout python3 also rather convenient given the recently added python bindings)

[levydsa]

Committing this sort of locks out anyone from doing anything else with direnv though (which layout python3 also rather convenient given the recently added python bindings)

@thisismiller, I addressed this in 453571e. Take a look :)

[penberg]

I don't use Flake or nix so... does this look better now, @thisismiller?

[levydsa]

@penberg, this can be safely merged. The configuration checks if nix is present. Example on another repo: https://github.com/ghostty-org/ghostty/blob/6ef757a8f85db7a124d370378850339a899c9e65/.envrc

[thisismiller]

Sorry for making unconstructive complaints. I'm already a direnv user, but not a nix user. So committing a .envrc file means I'd just have to carry around a conflict permanently, or figure out that one line of git magic to ignore conflicts from a specific file name.

I don't oppose committing a file with the direnv script for flake if that's helpful for folk, but I'd suggest maybe adding .envrc to .gitignore and offering the current script as .envrc_flake. We can then append to the README setup instructions a "if you're a direnv and flake user, then do echo source_env .envrc_flake > .envrc".

If most people are flake users already and I'm the odd one out, then appending a source_env_if_exists .envrc_custom to the bottom of the current script (and adding .envrc_custom to .gitignore) at least lets me keep the layout python3 I currently have without have a permanent conflict.

[levydsa]

@thisismiller, don't be sorry, your input is very much valid. I said it was safe to merge because it wouldn't just break for users that don't use nix. Can we just add layout python3 to a .envrc on the repo itself? I have added it to a nested .envrc under bindings/python. Tell me if that works :)

[thisismiller]

Unfortunately, the layout python3 also needs to be at the top level, because otherwise when you run cargo build at the root of the limbo checkout, cargo won't pick up the .envrc within bindings/python. My impression was that flake and layout python3 are just two different ways of achieving the same thing (with flake doing a superset), and so the two are just in direct conflict.

[haaawk]

Wouldn't it make sense to keep this out of the repo? It seems very specific to individual preferences. I don't think commiting tools configs to the repo is a good idea unless usage of that tools is mandatory to all contributors. How are direnv and nix more special than thousands other tools?

[levydsa]

@haaawk, I understand that this looks very specific, but the direnv and nix flakes are very project specific. Having this tools available is just nice to have. We can accommodate the needs of other developers that use, in this case, layout python3.

Having layout python3 in the configuration doesn't affect the nix devshell at all. The project has a Pipfile and a bunch of python scripts for tests (I only saw that now), so it makes total sense to have the environment configured for that.

I've added it to the top level .envrc. @thisismiller, tell me if that works.

[thisismiller]

I think this is no longer needed now, right?

[levydsa]

Direnv generates this folder for me. Seems to be a cache of some sort.

[thisismiller]

If use flake and layout python3 aren't conflicting for you, then yes, this makes it no longer conflicting for me. Thanks!

To haaawk's point, I'm still not sure that it's good to specify one canonical .envrc that should work for everyone, as someone might show up in the future complaining that they can't override some cargo env var for limbo or something similar, but we can also figure out what to do when we reach that point.

[levydsa]

It works for me :) Thanks for showing that feature, I didn't knew about it.