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//! Serializable errors with context
use std::{error::Error as _, fmt::Display, io, result};
use serde::{Deserialize, Serialize};
pub trait Contextualizable: Sized {
type Output;
fn with_context<C: Display, F: FnOnce() -> C>(self, f: F) -> Self::Output;
fn context<C: Display>(self, c: C) -> Self::Output {
self.with_context(|| c)
}
}
#[derive(Clone, Debug, PartialEq, Eq, Deserialize, Serialize)]
pub enum ErrorCause {
Code(i32),
String(String),
}
impl Display for ErrorCause {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
ErrorCause::Code(code) => io::Error::from_raw_os_error(*code).fmt(f),
ErrorCause::String(string) => f.write_str(string),
}
}
}
#[derive(Clone, Debug, PartialEq, Eq, Deserialize, Serialize)]
pub struct Error {
pub cause: ErrorCause,
pub context: Vec<String>,
}
impl Error {
pub fn new<D: Display>(cause: D) -> Self {
Error {
cause: ErrorCause::String(cause.to_string()),
context: Vec::new(),
}
}
pub fn from_io(err: &io::Error) -> Self {
if let Some(source) = err
.source()
.and_then(|source| source.downcast_ref::<io::Error>())
{
return Error::from_io(source).context(err.to_string());
}
let cause = match err.raw_os_error() {
Some(code) => ErrorCause::Code(code),
None => ErrorCause::String(err.to_string()),
};
Error {
cause,
context: vec![],
}
}
}
impl Display for Error {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str("Error: ")?;
let mut it = self.context.iter().rev();
if let Some(ctx) = it.next() {
write!(f, "{}\n\nCaused by:\n ", ctx)?;
for ctx in it {
write!(f, "{}\n ", ctx)?;
}
}
self.cause.fmt(f)
}
}
impl Contextualizable for Error {
type Output = Error;
fn with_context<C: Display, F: FnOnce() -> C>(self, f: F) -> Self::Output {
let Error { cause, mut context } = self;
context.push(f().to_string());
Error { cause, context }
}
}
impl<E> From<E> for Error
where
E: Into<io::Error>,
{
fn from(err: E) -> Self {
Error::from_io(&err.into())
}
}
pub type Result<T> = result::Result<T, Error>;
impl<T, E> Contextualizable for result::Result<T, E>
where
E: Into<Error>,
{
type Output = Result<T>;
fn with_context<C: Display, F: FnOnce() -> C>(self, f: F) -> Self::Output {
self.map_err(|err| err.into().with_context(f))
}
}
impl<T> Contextualizable for Option<T> {
type Output = Result<T>;
fn with_context<C: Display, F: FnOnce() -> C>(self, f: F) -> Self::Output {
self.ok_or_else(|| Error::new(f()))
}
}
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