Add an option to let DEVENV_ROOT be a relative path

[Atry]

This option lets DEVENV_ROOT and other devenv environment variables be relative paths, which works without --impure flag. However, some services may not support relative paths.

[domenkozar]

What's the motivation to have this setting? Having too many knobs like this makes things harder to test and support.

[Atry]

There is a TODO about this

# TODO: figure out how to get relative path without impure mode

[Atry]

I think there are users who don't want --impure

[bobvanderlinden]

There are generated configuration files that depend on DEVENV_ROOT. If it is set to . those configuration files will fail in strange ways.

Maybe adding an option for devenv.root:

options.devenv.root = mkOption { type = lib.types.path; };
config.assertions = [
  { assertion = config.devenv.root != ""; message = ''devenv.root must be set. This is set to PWD by default, but only if you're running Nix with --impure. Running with --impure is recommended. Otherwise you need to set it manually. "." is possible, but not recommended as there are integrations that need to presume this value to be absolute.''; }
];
config.devenv.root = mkDefault (buitlins.getEnv "PWD");
config.env.DEVENV_ROOT = config.devenv.root;

In flakes you can add a { devenv.root = "/path/to/your/dir"; } module to get around the issue. Or if you don't mind running into potential problems, use { devenv.root = "."; }.

I do agree that being able to call devenv in pure mode would have benefits, but using . at the moment is probably asking for hidden trouble/bugs.

[Atry]

There are generated configuration files that depend on DEVENV_ROOT.

Is it possible to make sure all generated configuration files include relative paths?

[Atry]

What exact generated files require absolute paths? Shall we add tests for enabling relative paths?

[Atry]

I think most of the usage of env.DEVENV_ROOT can be replaced with inputs.self

[domenkozar]

In the case of flakes, we could just use inputs.self!

[bobvanderlinden]

Is it possible to make sure all generated configuration files include relative paths?

It's a bit tricky. Some commands may be used in different directories while it should still refer to the .devenv/ directory.

For instance:

https://github.com/cachix/devenv/blob/4da6478ed21c3ab643bed241660c1e8d62be4371/src/modules/processes.nix#L53

It is possible to use $DEVENV_ROOT here at runtime, however, this goes wrong if there are devenv environments within devenv environments. You should still be able to use a script from a parent devenv environment and that still needs to be able to refer to the parent .devenv directory.

In the case of flakes, we could just use inputs.self!

:thinking: I wasn't aware of that input, but that makes a lot of sense!

[Atry]

It is possible to use $DEVENV_ROOT here at runtime, however, this goes wrong if there are devenv environments within devenv environments. You should still be able to use a script from a parent devenv environment and that still needs to be able to refer to the parent .devenv directory.

For shell scripts generated under .devenv/path/file, I would use "$(dirname "$0")/.." to find the work directory

[Atry]

toString inputs.self is a Nix store path, which is good for reading files added to git, but not good for reading or writing ignored files.

[domenkozar]

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