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use std::any::Any;
use std::fmt;
use std::io;
use super::Id;
use crate::util::SyncWrapper;
cfg_rt! {
/// Task failed to execute to completion.
pub struct JoinError {
repr: Repr,
id: Id,
}
}
enum Repr {
Cancelled,
Panic(SyncWrapper<Box<dyn Any + Send + 'static>>),
}
impl JoinError {
pub(crate) fn cancelled(id: Id) -> JoinError {
JoinError {
repr: Repr::Cancelled,
id,
}
}
pub(crate) fn panic(id: Id, err: Box<dyn Any + Send + 'static>) -> JoinError {
JoinError {
repr: Repr::Panic(SyncWrapper::new(err)),
id,
}
}
/// Returns true if the error was caused by the task being cancelled.
pub fn is_cancelled(&self) -> bool {
matches!(&self.repr, Repr::Cancelled)
}
/// Returns true if the error was caused by the task panicking.
///
/// # Examples
///
/// ```
/// use std::panic;
///
/// #[tokio::main]
/// async fn main() {
/// let err = tokio::spawn(async {
/// panic!("boom");
/// }).await.unwrap_err();
///
/// assert!(err.is_panic());
/// }
/// ```
pub fn is_panic(&self) -> bool {
matches!(&self.repr, Repr::Panic(_))
}
/// Consumes the join error, returning the object with which the task panicked.
///
/// # Panics
///
/// `into_panic()` panics if the `Error` does not represent the underlying
/// task terminating with a panic. Use `is_panic` to check the error reason
/// or `try_into_panic` for a variant that does not panic.
///
/// # Examples
///
/// ```should_panic
/// use std::panic;
///
/// #[tokio::main]
/// async fn main() {
/// let err = tokio::spawn(async {
/// panic!("boom");
/// }).await.unwrap_err();
///
/// if err.is_panic() {
/// // Resume the panic on the main task
/// panic::resume_unwind(err.into_panic());
/// }
/// }
/// ```
#[track_caller]
pub fn into_panic(self) -> Box<dyn Any + Send + 'static> {
self.try_into_panic()
.expect("`JoinError` reason is not a panic.")
}
/// Consumes the join error, returning the object with which the task
/// panicked if the task terminated due to a panic. Otherwise, `self` is
/// returned.
///
/// # Examples
///
/// ```should_panic
/// use std::panic;
///
/// #[tokio::main]
/// async fn main() {
/// let err = tokio::spawn(async {
/// panic!("boom");
/// }).await.unwrap_err();
///
/// if let Ok(reason) = err.try_into_panic() {
/// // Resume the panic on the main task
/// panic::resume_unwind(reason);
/// }
/// }
/// ```
pub fn try_into_panic(self) -> Result<Box<dyn Any + Send + 'static>, JoinError> {
match self.repr {
Repr::Panic(p) => Ok(p.into_inner()),
_ => Err(self),
}
}
/// Returns a [task ID] that identifies the task which errored relative to
/// other currently spawned tasks.
///
/// **Note**: This is an [unstable API][unstable]. The public API of this type
/// may break in 1.x releases. See [the documentation on unstable
/// features][unstable] for details.
///
/// [task ID]: crate::task::Id
/// [unstable]: crate#unstable-features
#[cfg(tokio_unstable)]
#[cfg_attr(docsrs, doc(cfg(tokio_unstable)))]
pub fn id(&self) -> Id {
self.id
}
}
impl fmt::Display for JoinError {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
match &self.repr {
Repr::Cancelled => write!(fmt, "task {} was cancelled", self.id),
Repr::Panic(_) => write!(fmt, "task {} panicked", self.id),
}
}
}
impl fmt::Debug for JoinError {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
match &self.repr {
Repr::Cancelled => write!(fmt, "JoinError::Cancelled({:?})", self.id),
Repr::Panic(_) => write!(fmt, "JoinError::Panic({:?}, ...)", self.id),
}
}
}
impl std::error::Error for JoinError {}
impl From<JoinError> for io::Error {
fn from(src: JoinError) -> io::Error {
io::Error::new(
io::ErrorKind::Other,
match src.repr {
Repr::Cancelled => "task was cancelled",
Repr::Panic(_) => "task panicked",
},
)
}
}