Struct EnvRung 

pub struct EnvRung<'a> {
    pub locator: Option<&'a str>,
    pub domain_id: Option<u32>,
    pub mode: Option<SessionMode>,
    pub node_name: Option<&'a str>,
    pub namespace: Option<&'a str>,
    pub rmw: Option<&'a str>,
}

The environment rung of precedence model A, as VALUES.

issue 0687 — try_resolve used to take hosted_env: bool and read the process environment itself, which is why this crate needed std. A rung is a set of values, not a place they come from: the hosted edge (nros::env::resolve_hosted) reads $NROS_LOCATOR, $ROS_DOMAIN_ID, $NROS_SESSION_MODE, $NROS_NODE_NAME and $NROS_RMW and fills this in; an embedded caller that wants the same precedence from some other source (a settings partition, a Kconfig blob) can fill it too, which the bool could never express.

None on a field means “the environment did not speak” — resolution falls through to baked, then to the compiled default. The old bool’s hosted_env=false is None here at the whole-rung level.

Fields

locator: Option<&'a str>

$NROS_LOCATOR (the retired ZENOH_LOCATOR is refused at the edge).

domain_id: Option<u32>

$ROS_DOMAIN_ID, already parsed — a malformed value is the EDGE’s error (BootConfigError::DomainIdParse), reported before it gets here, because only the edge knows the text.

mode: Option<SessionMode>

$NROS_SESSION_MODE (the retired ZENOH_MODE is refused at the edge).

node_name: Option<&'a str>

$NROS_NODE_NAME.

namespace: Option<&'a str>

$NROS_NODE_NAMESPACE.

Issue 0794 — this rung did not exist, so the namespace had TWO levels (explicit, baked) where every other field of this struct had three, and RFC-0045 said nothing about the asymmetry. It was not a decision that a namespace is un-overridable identity: node_name is identity too and has always had its rung, and ROS 2 itself honours $ROS_NAMESPACE. It was the same unwired-producer shape as the baked rung one level down.

The name is $NROS_NODE_NAMESPACE — the nano-ros vocabulary, matching $NROS_NODE_NAME. $ROS_NAMESPACE is deliberately NOT folded in, for the reason rmw_selector does not fold in $RMW_IMPLEMENTATION: a variable this tree does not own would start deciding identity for every nano-ros process in a sourced ROS shell, which is a behaviour change no nano-ros config asked for.

rmw: Option<&'a str>

$NROS_RMW — the backend selector, resolved through nros::rmw_selector so every reader agrees on what “unset” means.

Trait Implementations

impl<'a> Clone for EnvRung<'a>

fn clone(&self) -> EnvRung<'a>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a> Copy for EnvRung<'a>

impl<'a> Debug for EnvRung<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a> Default for EnvRung<'a>

fn default() -> EnvRung<'a>

Returns the “default value” for a type.