nix_direnv_watch_file should be watch_file

[infinisil]

If you want to make sure your environment is both automatically updated when files change, and updated to the correct value, and you don't know if the user has nix-direnv installed, you need to do something like this:

if has nix_direnv_watch_file; then
  nix_direnv_watch_file file.nix
else
  watch_file file.nix
fi

use nix

It would be much nicer if nix-direnv provided its own version of watch_file instead, such that a simple watch_file file.nix works.

nix-direnv would then also have the correct behavior by default for projects whose .envrc doesn't do anything special for nix-direnv.

[Mic92]

What if make nix_watches+=() the api? This will work also if you don't have nix-direnv. I am a bit hesitant off monkey patching more direnv builtins.

[infinisil]

As far as I can see, there's never a case where you'd want to watch_file but not nix_direnv_watch_file, so overriding it would be fine.

Using nix_watches+=() would still require repos that were just considering direnv to make adjustments for nix-direnv.

[Mic92]

@zimbatm I guess there is no other api to check if a file is beeing watched by direnv?

[bbenne10]

@zimbatm has explicitly asked that we avoid monkey patching the direnv stdlib in this particular manner. I will continue honoring that request moving forward.

However, I see no reason you couldn't do this:

if has nix_direnv_watch_file; then
  alias wf=nix_direnv_watch_file
else
  alias wf=watch_file
fi

wf flake.nix

[infinisil]

The problem with any approach that doesn't just use watch_file is that it requires all projects using direnv to explicitly add support for nix-direnv as above, and otherwise their caching is just broken for all nix-direnv users.

[bbenne10]

This is true. At work, we've taken the approach that using or not using nix-direnv is a project specification, which makes this a decision that we don't allow non-principal developers to override (Of course, they can discuss and influence direction, but we commit our .envrc to git to keep it consistent). We then use source_url to pin to a revision.

Yes - I agree that this is a bit frustrating. But the fact that both direnv and nix-direnv provide somewhat matching interfaces is a bit of an implementation detail in my eyes (and honestly - one I wish I could undo at this point. The confusion between the two projects has come up repeatedly in issues. I'd much prefer use_flake_cache or something...)

[infinisil]

Tbh nix-direnv should either just be built into direnv directly, or be some sort of plugin for it.

[Mic92]

You can use it as a plugin. Just add this to your project:

if ! has nix_direnv_version || ! nix_direnv_version 2.4.0; then
  source_url "https://raw.githubusercontent.com/nix-community/nix-direnv/2.4.0/direnvrc" "sha256-XQzUAvL6pysIJnRJyR7uVpmUSZfc7LSgWQwq/4mBr1U="
fi

[Mic92]

Using a different name would have been also an annoyance, when a project comes with an .envrc that just uses use nix and everything gets slow again.