Use YAML for config

[shivaraj-bh]

resolves #343

If the flake url is a local path and om.yaml exists in the project root, omnix will not invoke nix eval .#om.

[srid]

This looks good so far. Can we improve the OmConfig::get interface so as to resolve and avoid unnecessary nix command runs? See #339 (comment)

[srid]

I just realized I got confused (see "catchall" comment here) by YamlNotFound. Because it a value of OmConfigError, I somehow confused it to refer to yaml errors.

Just get rid of YamlNotFound and have from_yaml return Option<Self> instead, so the caller can do fallback on None.

[shivaraj-bh]

If from_yaml returns Option<Self> will we not be silently skipping over errors while parsing the YAML?

[srid]

No, I meant:

    async fn from_yaml(cmd: &NixCmd, flake_url: &FlakeUrl) -> Result<Option<Self>, OmConfigError> {

[shivaraj-bh]

This looks good so far. Can we improve the OmConfig::get interface so as to resolve and avoid unnecessary nix command runs? See #339 (comment)

Aren’t those nix commands the result of the checks in preShell?

omnix/crates/omnix-develop/src/core.rs

Lines 45 to 57 in af87950

	pub async fn develop_on_pre_shell(prj: &Project) -> anyhow::Result<()> {
	// Run relevant `om health` checks
	let health = NixHealth::from_om_config(&prj.om_config)?;
	let nix_info = NixInfo::get()
	.await
	.as_ref()
	.with_context(|| "Unable to gather nix info")?;
	let mut relevant_checks: Vec<&'_ dyn Checkable> =
	vec![&health.nix_version, &health.rosetta, &health.max_jobs];
	if !health.caches.required.is_empty() {
	relevant_checks.push(&health.trusted_users);
	};

[srid]

Aren’t those nix commands the result of the checks in preShell?

While we can't avoid running nix commands in preShell (for now), we certainly can avoid that in postShell (which too will be run as part of direnv invocation):