Enum Error 

#[non_exhaustive]
pub enum Error {
    NoSource {
        tried: String,
    },
    Uninitialized {
        source_kind: SourceKind,
        path: PathBuf,
    },
    Io {
        source_kind: SourceKind,
        path: PathBuf,
        source: Error,
    },
    Malformed {
        source_kind: SourceKind,
        reason: String,
    },
    Platform {
        source_kind: SourceKind,
        reason: String,
    },
}

Errors returned by crate::Resolver::resolve.

Every variant except Error::NoSource carries the SourceKind that produced it, so logs and error messages unambiguously identify which source failed. Error::source_kind exposes the field uniformly across variants.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

NoSource

Every configured source was tried and none produced a usable identity.

Fields

tried: String

Comma-separated list of sources that were attempted.

Uninitialized

A source file was present but contained the systemd uninitialized sentinel. The caller should not treat this as a valid identity — every host in this state would hash to the same UUID.

Fields

source_kind: SourceKind

Which source produced the error.

path: PathBuf

Path of the offending file.

Io

I/O failure while reading a source file. Command-spawn failures are reported as Error::Platform instead — this variant’s path field is always a real filesystem path.

Fields

source_kind: SourceKind

Which source produced the error.

path: PathBuf

Filesystem path that produced the error.

source: Error

Underlying I/O error.

Malformed

A source returned a value that is not a well-formed identifier (empty after trimming, wrong shape, invalid UTF-8, …).

Fields

source_kind: SourceKind

Which source produced the error.

reason: String

Human-readable reason.

Platform

Platform-specific lookup failed (registry query, syscall, ioreg, cloud metadata contract violation, …).

Fields

source_kind: SourceKind

Which source produced the error.

reason: String

Human-readable reason.

Implementations

impl Error

pub fn source_kind(&self) -> Option<SourceKind>

The source that produced this error, if the variant carries one.

Returns None only for Error::NoSource, which reports that every source was tried and none produced a value — that error doesn’t belong to any single source.

pub fn is_recoverable(&self) -> bool

Whether this error is reasonable for the caller to recover from at runtime (log a warning, mint a per-run placeholder UUID, etc.) rather than treat as a fatal configuration problem.

• Error::NoSource → true. No source produced a value, but the crate is behaving correctly; the caller’s chain simply doesn’t match the environment. Apps often handle this by falling back to their own ID scheme.
• All other variants → false. They indicate a concrete fault (sentinel, I/O failure, malformed source value, platform-tool failure) that won’t fix itself on retry; the caller should surface them to the operator.

This classification is a guideline, not a hard contract. A particular deployment might reasonably treat an Io error on /etc/machine-id as recoverable (keep going with the next source) — the method exists to give the common case a one-liner, not to remove the caller’s judgement.

Trait Implementations

impl Debug for Error

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

Formats the value using the given formatter.

impl Display for Error

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

Formats the value using the given formatter.

impl Error for Error

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.