Struct Error 

pub struct Error { /* private fields */ }

An error that can occur in this crate.

The most common type of error is a result of overflow. But other errors exist as well:

• Time zone database lookup failure.
• Configuration problem. (For example, trying to round a span with calendar units without providing a relative datetime.)
• An I/O error as a result of trying to open a time zone database from a directory via TimeZoneDatabase::from_dir.
• Parse errors.

Introspection is limited

Other than implementing the std::error::Error trait when the std feature is enabled, the core::fmt::Debug trait and the core::fmt::Display trait, this error type currently provides very limited introspection capabilities. Simple predicates like Error::is_range are provided, but the predicates are not exhaustive. That is, there exist some errors that do not return true for any of the Error::is_* predicates.

Design

This crate follows the “One True God Error Type Pattern,” where only one error type exists for a variety of different operations. This design was chosen after attempting to provide finer grained error types. But finer grained error types proved difficult in the face of composition.

More about this design choice can be found in a GitHub issue about error types.

Implementations

impl Error

pub fn from_args<'a>(message: Arguments<'a>) -> Error

Creates a new error value from core::fmt::Arguments.

It is expected to use format_args! from Rust’s standard library (available in core) to create a core::fmt::Arguments.

Callers should generally use their own error types. But in some circumstances, it can be convenient to manufacture a Jiff error value specifically.

Core-only environments

In core-only environments without a dynamic memory allocator, error messages may be degraded in some cases. For example, if the given core::fmt::Arguments could not be converted to a simple borrowed &str, then this will ignore the input given and return an “unknown” Jiff error.

Example

use jiff::Error;

let err = Error::from_args(format_args!("something failed"));
assert_eq!(err.to_string(), "something failed");

pub fn is_range(&self) -> bool

Returns true when this error originated as a result of a value being out of Jiff’s supported range.

Example

use jiff::civil::Date;

assert!(Date::new(2025, 2, 29).unwrap_err().is_range());
assert!("2025-02-29".parse::<Date>().unwrap_err().is_range());
assert!(Date::strptime("%Y-%m-%d", "2025-02-29").unwrap_err().is_range());

pub fn is_invalid_parameter(&self) -> bool

Returns true when this error originated as a result of an invalid configuration of parameters to a function call.

This particular error category is somewhat nebulous, but it’s generally meant to cover errors that could have been statically prevented by Jiff with more types in its API. Instead, a smaller API is preferred.

Example: invalid rounding options

use jiff::{SpanRound, ToSpan, Unit};

let span = 44.seconds();
let err = span.round(
    SpanRound::new().smallest(Unit::Second).increment(45),
).unwrap_err();
// Rounding increments for seconds must divide evenly into `60`.
// But `45` does not. Thus, this is a "configuration" error.
assert!(err.is_invalid_parameter());

Example: invalid units

One cannot round a span between dates to units less than days:

use jiff::{civil::date, Unit};

let date1 = date(2025, 3, 18);
let date2 = date(2025, 12, 21);
let err = date1.until((Unit::Hour, date2)).unwrap_err();
assert!(err.is_invalid_parameter());

Similarly, one cannot round a span between times to units greater than hours:

use jiff::{civil::time, Unit};

let time1 = time(9, 39, 0, 0);
let time2 = time(17, 0, 0, 0);
let err = time1.until((Unit::Day, time2)).unwrap_err();
assert!(err.is_invalid_parameter());

pub fn is_crate_feature(&self) -> bool

Returns true when this error originated as a result of an operation failing because an appropriate Jiff crate feature was not enabled.

Example

use jiff::tz::TimeZone;

// This passes when the `tz-system` crate feature is NOT enabled.
assert!(TimeZone::try_system().unwrap_err().is_crate_feature());

Trait Implementations

impl Clone for Error

fn clone(&self) -> Error

Returns a duplicate of the value.

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

Performs copy-assignment from source.

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, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for Error

Available on crate feature std only.

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.