Struct Error

pub struct Error { /* private fields */ }

Expand description

Core Diagnostic wrapper type.

§`eyre` Users

You can just replace uses of eyre::Report with miette::Report.

Implementations§

§

impl Report

pub fn new<E>(error: E) -> Report
where E: Diagnostic + Send + Sync + 'static,

Create a new error object from any error type.

The error type must be thread safe and 'static, so that the Report will be as well.

If the error type does not provide a backtrace, a backtrace will be created here to ensure that a backtrace exists.

pub fn msg<M>(message: M) -> Report
where M: Display + Debug + Send + Sync + 'static,

Create a new error object from a printable error message.

If the argument implements std::error::Error, prefer Report::new instead which preserves the underlying error’s cause chain and backtrace. If the argument may or may not implement std::error::Error now or in the future, use miette!(err) which handles either way correctly.

Report::msg("...") is equivalent to miette!("...") but occasionally convenient in places where a function is preferable over a macro, such as iterator or stream combinators:

use futures::stream::{Stream, StreamExt, TryStreamExt};
use miette::{Report, Result};

async fn demo<S>(stream: S) -> Result<Vec<Output>>
where
    S: Stream<Item = Input>,
{
    stream
        .then(ffi::do_some_work) // returns Result<Output, &str>
        .map_err(Report::msg)
        .try_collect()
        .await
}

pub fn new_boxed(error: Box<dyn Diagnostic + Send + Sync>) -> Report

Create a new error object from a boxed [Diagnostic].

The boxed type must be thread safe and ’static, so that the Report will be as well.

Boxed Diagnostics don’t implement Diagnostic themselves due to trait coherence issues. This method allows you to create a Report from a boxed Diagnostic.

pub fn wrap_err<D>(self, msg: D) -> Report
where D: Display + Send + Sync + 'static,

Create a new error from an error message to wrap the existing error.

For attaching a higher level error message to a Result as it is propagated, the WrapErr extension trait may be more convenient than this function.

The primary reason to use error.wrap_err(...) instead of result.wrap_err(...) via the WrapErr trait would be if the message needs to depend on some data held by the underlying error:

pub fn context<D>(self, msg: D) -> Report
where D: Display + Send + Sync + 'static,

Compatibility re-export of wrap_err for interop with anyhow

pub fn chain(&self) -> Chain<'_>

An iterator of the chain of source errors contained by this Report.

This iterator will visit every error in the cause chain of this error object, beginning with the error that this error object was created from.

§Example

use miette::Report;
use std::io;

pub fn underlying_io_error_kind(error: &Report) -> Option<io::ErrorKind> {
    for cause in error.chain() {
        if let Some(io_error) = cause.downcast_ref::<io::Error>() {
            return Some(io_error.kind());
        }
    }
    None
}

pub fn root_cause(&self) -> &(dyn Error + 'static)

The lowest level cause of this error — this error’s cause’s cause’s cause etc.

The root cause is the last error in the iterator produced by chain().

pub fn is<E>(&self) -> bool
where E: Display + Debug + Send + Sync + 'static,

Returns true if E is the type held by this error object.

For errors constructed from messages, this method returns true if E matches the type of the message D or the type of the error on which the message has been attached. For details about the interaction between message and downcasting, see here.

pub fn downcast<E>(self) -> Result<E, Report>
where E: Display + Debug + Send + Sync + 'static,

Attempt to downcast the error object to a concrete type.

pub fn downcast_ref<E>(&self) -> Option<&E>
where E: Display + Debug + Send + Sync + 'static,

Downcast this error object by reference.

§Example

// If the error was caused by redaction, then return a tombstone instead
// of the content.
match root_cause.downcast_ref::<DataStoreError>() {
    Some(DataStoreError::Censored(_)) => Ok(Poll::Ready(REDACTED_CONTENT)),
    None => Err(error),
}