Aadd --impure flag when calling print-dev-env

[imfede]

Summary

Add --impure to the print-dev-env command, allowing flakes to access environment variables also in this step. Without this change, a flake that needs an env var to work will correctly build but then a shell could not be created.

This also solves #2196, signifying that other people encountered a similar problem.

How was it tested?

Both by

devbox run test

and manually, building the tool and locally checking that a flake would pick up variables (with builtins.getEnv) when activating a shell.

[mikeland73]

@imfede, thanks for the contribution!

IIRC we didn't make this impure in order to use the nix evaluation cache. That said, devbox uses its own caching as well, so we might not need that.

Could you add a feature flag to this and default it to disabled? That way you could start using it right away and we can test if it has any perf side-effects.

[mikeland73]

Please put this behind a disabled feature flag.

See featureflag package.

To enable for yourself you can use

DEVBOX_FEATURE_[NAME]=1

After we test a bit, if we don't see a performance issue we'll remove the flag and make it permanent.

Thanks again for contribution!

[imfede]

Thanks for the review!

My golang skills are practically non-existant, so I hope the end result is good enough. Let me know how can I improve on it if needed :)

[savil]

If I do the following steps, then I get an error here:

# build binary in dist/devbox
 % devbox run build
 
 # clear local state
 % rm -rf .devbox
 
 # install the devbox-repo's own packages
 % dist/devbox install
Info: Ensuring packages are installed.
✓ Computed the Devbox environment.
Error: nix: command error: nix --extra-experimental-features ca-derivations --option experimental-features 'nix-command flakes fetch-closure' print-dev-env --json  path:/Users/savil/code/jetpack/devbox/.devbox/gen/flake: unexpected argument 'path:/Users/savil/code/jetpack/devbox/.devbox/gen/flake': exit code 1

Error: There was an internal error. Run with DEVBOX_DEBUG=1 for a detailed error message, and consider reporting it at https://github.com/jetify-com/devbox/issues

I think the issue is with the empty argument.

I think you could do:

		cmd := command("print-dev-env", "--json")
		if featureflag.ImpurePrintDevEnv.Enabled() {
			cmd.Args = append(cmd.Args, "--impure")
		}
		cmd.Args = append(cmd.Args, "path:"+flakeDirResolved)

[imfede]

Weird, I thought I had tested it without the feature flag active.

Thanks for spotting this, I have pushed a fix following your suggestion.

[savil]

LGTM thanks for sending this!

Mike, said lgtm in our chat program

[imfede]

Thanks for the reviews! Out of information, do you have a plan on when this could be released?