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use std::{error::Error as StdError, fmt};
use crate::{Chain, Error};
mod chain;
mod macros;
pub(crate) mod wrap;
impl Error {
/// Create a new error object from any error type.
///
/// The error type must be thread-safe and `'static`, so that the `Error`
/// will be as well.
pub fn new<E>(error: E) -> Self
where
E: StdError + Send + Sync + 'static,
{
Self {
inner: error.into(),
help: None,
}
}
/// Create a new error object from a printable error message.
///
/// If the argument implements [`std::error::Error`], prefer [`Error::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 [`error_from!(err)`](`crate::error_from`)
/// which handles either way correctly.
///
/// `Error::msg("...")` is equivalent to `error_from!("...")` but
/// occasionally convenient in places where a function is preferable over a
/// macro, such as iterator or stream combinators:
///
/// ```
/// # /*
/// use narrate::{Error, Result};
/// use futures::stream::{Stream, StreamExt, TryStreamExt};
///
/// 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(Error::msg)
/// .try_collect()
/// .await
/// }
/// # */
/// ```
pub fn msg<M>(message: M) -> Self
where
M: fmt::Display + fmt::Debug + Send + Sync + 'static,
{
Self {
inner: anyhow::Error::msg(message),
help: None,
}
}
/// Convert an [`anyhow::Error`] into an error object.
///
/// Due to the generic implementation of [`From`] for [`Error`]: we cannot
/// add a `From<anyhow::Error>` impl. Use this instead.
#[inline]
pub fn from_anyhow(error: anyhow::Error) -> Self {
Self {
inner: error,
help: None,
}
}
/// Wrap the error value with additional context.
///
/// For attaching context to a `Result` as it is propagated, the
/// [`ErrorWrap`](crate::ErrorWrap) extension trait may be more convenient than this function.
///
/// The primary reason to use `error.warp(...)` instead of
/// `result.warp(...)` via the `ErrorWrap` trait would be if the context
/// needs to depend on some data held by the underlying error:
///
/// ```
/// # use std::fmt::{self, Debug, Display};
/// #
/// # type T = ();
/// #
/// # impl std::error::Error for ParseError {}
/// # impl Debug for ParseError {
/// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
/// # unimplemented!()
/// # }
/// # }
/// # impl Display for ParseError {
/// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
/// # unimplemented!()
/// # }
/// # }
/// #
/// use narrate::Result;
/// use std::fs::File;
/// use std::path::Path;
///
/// struct ParseError {
/// line: usize,
/// column: usize,
/// }
///
/// fn parse_impl(file: File) -> Result<T, ParseError> {
/// # /*
/// ...
/// # */
/// # unimplemented!()
/// }
///
/// pub fn parse(path: impl AsRef<Path>) -> Result<T> {
/// let file = File::open(&path)?;
/// parse_impl(file).map_err(|error| {
/// let context = format!(
/// "only the first {} lines of {} are valid",
/// error.line, path.as_ref().display(),
/// );
/// narrate::Error::new(error).wrap(context)
/// })
/// }
/// ```
pub fn wrap<C>(self, context: C) -> Self
where
C: fmt::Display + Send + Sync + 'static,
{
Self {
inner: self.inner.context(context),
help: self.help,
}
}
/// Returns true if `E` is the type held by this error object.
///
/// For wrapped errors, this method returns true if `E` matches the
/// type of the context `C` **or** the type of the error on which the
/// context has been attached.
pub fn is<E>(&self) -> bool
where
E: fmt::Display + fmt::Debug + Send + Sync + 'static,
{
self.downcast_ref::<E>().is_some()
}
/// Attempt to downcast the error object to a concrete type.
pub fn downcast<E>(self) -> Result<E, Self>
where
E: fmt::Display + fmt::Debug + Send + Sync + 'static,
{
self.inner.downcast().map_err(Self::from_anyhow)
}
/// Downcast this error object by reference.
///
/// # Example
///
/// ```
/// # use narrate::error_from;
/// # use std::fmt::{self, Display};
/// # use std::task::Poll;
/// #
/// # #[derive(Debug)]
/// # enum DataStoreError {
/// # Censored(()),
/// # }
/// #
/// # impl Display for DataStoreError {
/// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
/// # unimplemented!()
/// # }
/// # }
/// #
/// # impl std::error::Error for DataStoreError {}
/// #
/// # const REDACTED_CONTENT: () = ();
/// #
/// # let error = error_from!("...");
/// # let root_cause = &error;
/// #
/// # let ret =
/// // 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),
/// }
/// # ;
/// ```
pub fn downcast_ref<E>(&self) -> Option<&E>
where
E: fmt::Display + fmt::Debug + Send + Sync + 'static,
{
self.inner.downcast_ref()
}
/// Downcast this error object by mutable reference.
pub fn downcast_mut<E>(&mut self) -> Option<&mut E>
where
E: fmt::Display + fmt::Debug + Send + Sync + 'static,
{
self.inner.downcast_mut()
}
/// An iterator of the chain of source errors contained by this Error.
///
/// 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 narrate::Error;
/// use std::io;
///
/// pub fn underlying_io_error_kind(error: &Error) -> 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 chain(&self) -> Chain {
self.inner.chain().into()
}
/// 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()`][Error::chain].
pub fn root_cause(&self) -> &(dyn StdError + 'static) {
self.inner.root_cause()
}
/// Get a reference to this error's help message
#[inline]
pub fn help(&self) -> Option<&str> {
self.help.as_ref().map(AsRef::as_ref)
}
/// Set this error's help message to an owned [`String`]
#[inline]
#[deprecated]
pub fn set_help_owned(&mut self, msg: String) {
self.help = Some(HelpMsg::Owned(msg));
}
/// Set this error's help message to a static `&str`
#[inline]
#[deprecated]
pub fn set_help(&mut self, msg: &'static str) {
self.help = Some(HelpMsg::Static(msg));
}
/// Add a 'static help message to the Error.
///
/// Use this method to add a plain help [`str`]. If you need to format the
/// message, or add an owned [`String`], use
/// [`add_help_with`](Self::add_help_with) instead.
///
/// If the Error already has existing help text, this method will append the
/// new message to it (on a new line). This is done deliberately because the
/// last help message should be most visible.
///
/// You can add help to any `Result` that might contain a
/// [`std::error::Error`], by using the [`ErrorWrap`](crate::ErrorWrap)
/// trait.
///
/// # Examples
///
/// Add help to a constructed `Error`.
///
/// ```
/// # use std::fmt;
/// #
/// # #[derive(Debug)]
/// # struct AppError;
/// #
/// # impl fmt::Display for AppError {
/// # fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
/// # write!(f, "application error")
/// # }
/// # }
/// #
/// # impl std::error::Error for AppError {}
/// #
/// use narrate::Error;
///
/// let mut error = Error::new(AppError);
/// error.add_help("help message");
/// ```
///
/// Add multiple help messages.
///
///
/// ```
/// # use std::fmt;
/// #
/// # #[derive(Debug)]
/// # struct AppError;
/// #
/// # impl fmt::Display for AppError {
/// # fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
/// # write!(f, "application error")
/// # }
/// # }
/// #
/// # impl std::error::Error for AppError {}
/// #
/// use narrate::{Error, ErrorWrap, Result};
///
/// fn main() {
/// let err = outer().unwrap_err();
/// // outer help appended on a new line
/// let expected = "inner help\nouter help";
/// assert_eq!(err.help(), Some(expected));
/// }
///
/// fn outer() -> Result<()> {
/// // uses the ErrorWrap trait to add help to the Result
/// inner().add_help("outer help")?;
/// Ok(())
/// }
///
/// fn inner() -> Result<()> {
/// let mut error = Error::new(AppError);
/// error.add_help("inner help");
/// Err(error)
/// }
/// ```
pub fn add_help(&mut self, help: &'static str) {
match self.help {
Some(HelpMsg::Owned(ref mut existing)) => {
existing.push('\n');
existing.push_str(help);
}
Some(HelpMsg::Static(existing)) => {
self.help = Some(HelpMsg::Owned(format!("{}\n{}", existing, help)))
}
None => self.help = Some(HelpMsg::Static(help)),
}
}
/// Add a computed help message to the Error.
///
/// Use this method to add a formatted or computed [`String`]. If you are
/// adding a `'static str` you should use [`add_help`](Self::add_help)
/// instead.
///
/// This method takes any closure that produces a value that implements
/// [`Display`](fmt::Display), [`Send`], [`Sync`] and `'static`.
///
/// If the Error already has existing help text, this method will append the
/// new message to it (on a new line). This is done deliberately because the
/// last help message should be most visible.
///
/// You can add help to any `Result` that might contain a
/// [`std::error::Error`], by using the [`ErrorWrap`](crate::ErrorWrap)
/// trait.
///
/// # Examples
///
/// Add formatted help.
///
/// ```
/// # use std::path::PathBuf;
/// use narrate::{CliError, Error};
///
/// let path = PathBuf::from("/path/to/file");
/// let mut error = Error::new(CliError::CreateFile(path.clone()));
/// error.add_help_with(|| format!("helpful message about path: {}", path.display()));
/// ```
///
/// Add existing value.
///
/// ```
/// use narrate::error_from;
///
/// let mut error = error_from!("error msg");
/// let help = String::from("help msg");
/// error.add_help_with(|| help);
/// ```
pub fn add_help_with<C, F>(&mut self, f: F)
where
C: fmt::Display + Send + Sync + 'static,
F: FnOnce() -> C,
{
self.help = Some(HelpMsg::Owned(match self.help() {
Some(existing) => format!("{}\n{}", existing, f()),
None => f().to_string(),
}));
}
}
impl<E> From<E> for Error
where
E: StdError + Send + Sync + 'static,
{
fn from(err: E) -> Self {
Self {
inner: err.into(),
help: None,
}
}
}
#[derive(Debug)]
pub(crate) enum HelpMsg {
Owned(String),
Static(&'static str),
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.inner.fmt(f)
}
}
impl fmt::Debug for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
if f.alternate() {
return fmt::Debug::fmt(&self.inner, f);
}
write!(f, "{}", self.inner)?;
for cause in self.inner.chain().skip(1) {
write!(f, "\nCause: {cause}")?;
}
if let Some(ref help) = self.help {
write!(f, "\n\n{help}")?;
}
Ok(())
}
}
impl AsRef<str> for HelpMsg {
fn as_ref(&self) -> &str {
match self {
HelpMsg::Owned(ref s) => s,
HelpMsg::Static(s) => s,
}
}
}
impl fmt::Display for HelpMsg {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
HelpMsg::Owned(help) => help.fmt(f),
HelpMsg::Static(help) => help.fmt(f),
}
}
}
impl<'a> PartialEq<&'a str> for HelpMsg {
fn eq(&self, r: &&'a str) -> bool {
match self {
Self::Owned(l) => l == r,
Self::Static(l) => l == r,
}
}
}
impl From<Error> for anyhow::Error {
fn from(err: Error) -> Self {
err.inner
}
}