Source code
Revision control
Copy as Markdown
Other Tools
#![allow(
clippy::nonstandard_macro_braces,
)]
mod drop;
use crate::drop::{DetectDrop, Flag};
use anyhow::{Context, Error, Result};
use std::fmt::{self, Display};
use thiserror::Error;
#[test]
fn test_inference() -> Result<()> {
let x = "1";
let y: u32 = x.parse().context("...")?;
assert_eq!(y, 1);
Ok(())
}
macro_rules! context_type {
($name:ident) => {
#[derive(Debug)]
struct $name {
message: &'static str,
#[allow(dead_code)]
drop: DetectDrop,
}
impl Display for $name {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.write_str(self.message)
}
}
};
}
context_type!(HighLevel);
context_type!(MidLevel);
#[derive(Error, Debug)]
#[error("{message}")]
struct LowLevel {
message: &'static str,
drop: DetectDrop,
}
struct Dropped {
low: Flag,
mid: Flag,
high: Flag,
}
impl Dropped {
fn none(&self) -> bool {
!self.low.get() && !self.mid.get() && !self.high.get()
}
fn all(&self) -> bool {
self.low.get() && self.mid.get() && self.high.get()
}
}
fn make_chain() -> (Error, Dropped) {
let dropped = Dropped {
low: Flag::new(),
mid: Flag::new(),
high: Flag::new(),
};
let low = LowLevel {
message: "no such file or directory",
drop: DetectDrop::new(&dropped.low),
};
// impl Context for Result<T, E>
let mid = Err::<(), LowLevel>(low)
.context(MidLevel {
message: "failed to load config",
drop: DetectDrop::new(&dropped.mid),
})
.unwrap_err();
// impl Context for Result<T, Error>
let high = Err::<(), Error>(mid)
.context(HighLevel {
message: "failed to start server",
drop: DetectDrop::new(&dropped.high),
})
.unwrap_err();
(high, dropped)
}
#[test]
fn test_downcast_ref() {
let (err, dropped) = make_chain();
assert!(!err.is::<String>());
assert!(err.downcast_ref::<String>().is_none());
assert!(err.is::<HighLevel>());
let high = err.downcast_ref::<HighLevel>().unwrap();
assert_eq!(high.to_string(), "failed to start server");
assert!(err.is::<MidLevel>());
let mid = err.downcast_ref::<MidLevel>().unwrap();
assert_eq!(mid.to_string(), "failed to load config");
assert!(err.is::<LowLevel>());
let low = err.downcast_ref::<LowLevel>().unwrap();
assert_eq!(low.to_string(), "no such file or directory");
assert!(dropped.none());
drop(err);
assert!(dropped.all());
}
#[test]
fn test_downcast_high() {
let (err, dropped) = make_chain();
let err = err.downcast::<HighLevel>().unwrap();
assert!(!dropped.high.get());
assert!(dropped.low.get() && dropped.mid.get());
drop(err);
assert!(dropped.all());
}
#[test]
fn test_downcast_mid() {
let (err, dropped) = make_chain();
let err = err.downcast::<MidLevel>().unwrap();
assert!(!dropped.mid.get());
assert!(dropped.low.get() && dropped.high.get());
drop(err);
assert!(dropped.all());
}
#[test]
fn test_downcast_low() {
let (err, dropped) = make_chain();
let err = err.downcast::<LowLevel>().unwrap();
assert!(!dropped.low.get());
assert!(dropped.mid.get() && dropped.high.get());
drop(err);
assert!(dropped.all());
}
#[test]
fn test_unsuccessful_downcast() {
let (err, dropped) = make_chain();
let err = err.downcast::<String>().unwrap_err();
assert!(dropped.none());
drop(err);
assert!(dropped.all());
}
#[test]
fn test_root_cause() {
let (err, _) = make_chain();
assert_eq!(err.root_cause().to_string(), "no such file or directory");
}