Function plan_export 

pub fn plan_export(
    config: &Config,
    alias: &str,
) -> Result<ExportPlan, ExportError>

Compute the export closure for alias.

Fails only on an unknown alias or a serialization fault. A source config with dangling references plans without complaint — the unresolvable entries are simply absent from the closure — and is caught when the closure is rendered, which is the last point at which its final content is known. See render_config_toml.