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use core::{
cell::Cell,
sync::atomic::{AtomicUsize, Ordering::SeqCst},
};
use once_cell::unsync::OnceCell;
#[test]
fn once_cell() {
let c = OnceCell::new();
assert!(c.get().is_none());
c.get_or_init(|| 92);
assert_eq!(c.get(), Some(&92));
c.get_or_init(|| panic!("Kabom!"));
assert_eq!(c.get(), Some(&92));
}
#[test]
fn once_cell_with_value() {
const CELL: OnceCell<i32> = OnceCell::with_value(12);
let cell = CELL;
assert_eq!(cell.get(), Some(&12));
}
#[test]
fn once_cell_get_mut() {
let mut c = OnceCell::new();
assert!(c.get_mut().is_none());
c.set(90).unwrap();
*c.get_mut().unwrap() += 2;
assert_eq!(c.get_mut(), Some(&mut 92));
}
#[test]
fn once_cell_drop() {
static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
struct Dropper;
impl Drop for Dropper {
fn drop(&mut self) {
DROP_CNT.fetch_add(1, SeqCst);
}
}
let x = OnceCell::new();
x.get_or_init(|| Dropper);
assert_eq!(DROP_CNT.load(SeqCst), 0);
drop(x);
assert_eq!(DROP_CNT.load(SeqCst), 1);
}
#[test]
fn once_cell_drop_empty() {
let x = OnceCell::<String>::new();
drop(x);
}
#[test]
fn clone() {
let s = OnceCell::new();
let c = s.clone();
assert!(c.get().is_none());
s.set("hello".to_string()).unwrap();
let c = s.clone();
assert_eq!(c.get().map(String::as_str), Some("hello"));
}
#[test]
fn get_or_try_init() {
let cell: OnceCell<String> = OnceCell::new();
assert!(cell.get().is_none());
let res = std::panic::catch_unwind(|| cell.get_or_try_init(|| -> Result<_, ()> { panic!() }));
assert!(res.is_err());
assert!(cell.get().is_none());
assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
assert_eq!(cell.get_or_try_init(|| Ok::<_, ()>("hello".to_string())), Ok(&"hello".to_string()));
assert_eq!(cell.get(), Some(&"hello".to_string()));
}
#[test]
fn from_impl() {
assert_eq!(OnceCell::from("value").get(), Some(&"value"));
assert_ne!(OnceCell::from("foo").get(), Some(&"bar"));
}
#[test]
fn partialeq_impl() {
assert!(OnceCell::from("value") == OnceCell::from("value"));
assert!(OnceCell::from("foo") != OnceCell::from("bar"));
assert!(OnceCell::<String>::new() == OnceCell::new());
assert!(OnceCell::<String>::new() != OnceCell::from("value".to_owned()));
}
#[test]
fn into_inner() {
let cell: OnceCell<String> = OnceCell::new();
assert_eq!(cell.into_inner(), None);
let cell = OnceCell::new();
cell.set("hello".to_string()).unwrap();
assert_eq!(cell.into_inner(), Some("hello".to_string()));
}
#[test]
fn debug_impl() {
let cell = OnceCell::new();
assert_eq!(format!("{:#?}", cell), "OnceCell(Uninit)");
cell.set(vec!["hello", "world"]).unwrap();
assert_eq!(
format!("{:#?}", cell),
r#"OnceCell(
[
"hello",
"world",
],
)"#
);
}
#[test]
#[should_panic(expected = "reentrant init")]
fn reentrant_init() {
let x: OnceCell<Box<i32>> = OnceCell::new();
let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
x.get_or_init(|| {
let r = x.get_or_init(|| Box::new(92));
dangling_ref.set(Some(r));
Box::new(62)
});
eprintln!("use after free: {:?}", dangling_ref.get().unwrap());
}
#[test]
fn aliasing_in_get() {
let x = OnceCell::new();
x.set(42).unwrap();
let at_x = x.get().unwrap(); // --- (shared) borrow of inner `Option<T>` --+
let _ = x.set(27); // <-- temporary (unique) borrow of inner `Option<T>` |
println!("{}", at_x); // <------- up until here ---------------------------+
}
#[test]
fn arrrrrrrrrrrrrrrrrrrrrr() {
let cell = OnceCell::new();
{
let s = String::new();
cell.set(&s).unwrap();
}
}