Enum ConfigError 

#[non_exhaustive]
pub enum ConfigError {
    Io {
        path: PathBuf,
        source: Error,
    },
    Parse {
        path: PathBuf,
        source: Box<dyn Error + Send + Sync>,
    },
    UnknownFields {
        keys: Vec<String>,
    },
    EnvVar {
        key: String,
        source: VarError,
    },
    WatchFailed {
        source: Box<dyn Error + Send + Sync>,
    },
    Poisoned,
}

Loading, parsing, strict-validation, and watching failures.

Documented failure modes are part of the API contract; every variant lists the condition that produces it. The enum is #[non_exhaustive], so matches require a wildcard arm.

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.

Io

Reading a configuration file failed at the OS level — the file does not exist, lacks read permission, or the path is a directory. Produced by file layers and by watch when the watched file cannot be read back.

Fields

path: PathBuf

The file that could not be read.

source: Error

The underlying OS error.

Parse

One of:

• a configuration file failed to parse in its format,
• the file’s extension names a format whose feature is disabled (json, yaml),
• the merged configuration did not deserialize into the target type.

path is the file involved; for a merge/deserialization mismatch it is the most recently read file layer (or empty when no file layer contributed, e.g. a type mismatch introduced by env or overrides alone).

Fields

path: PathBuf

The file involved, or empty for a non-file deserialization mismatch (see above).

source: Box<dyn Error + Send + Sync>

The parser or serde error.

UnknownFields

load_strict found top-level keys that no field of the target type consumed. Nested unknown keys are deliberately not reported (see load_strict’s documentation for the precise contract).

Fields

keys: Vec<String>

The unconsumed top-level keys, sorted and deduplicated.

EnvVar

An environment variable matching the layer prefix carries a value that is not valid Unicode. Variables whose key is not valid Unicode can never match a str prefix and are skipped instead.

Fields

key: String

The (valid-Unicode) variable name.

source: VarError

The underlying variable error.

WatchFailed

File watching could not start — the platform watcher could not be created, the path could not be registered (typically: it does not exist), or the watcher thread could not be spawned. Produced only by watch (feature hot-reload).

Fields

source: Box<dyn Error + Send + Sync>

The underlying watcher error.

Poisoned

The watcher’s shared error-slot lock was poisoned by a panic in the watcher thread. Treat as fatal: reload state is indeterminate and the watcher must be stopped and rebuilt.

Trait Implementations

impl Debug for ConfigError

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

Formats the value using the given formatter.

impl Display for ConfigError

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

Formats the value using the given formatter.

impl Error for ConfigError

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.