cookie doctest failure

[Mark-Simulacrum]

The cookie crate is failing a doc test on CookieJar::iter: https://crater-reports.s3.amazonaws.com/beta-1.33-1/beta-2019-01-22/reg/cookie-0.11.0/log.txt

I haven't looked into this more but it seems to happen pretty consistently on beta and nightly but I haven't reproduced on stable.

cc @alexcrichton

[jonas-schievink]

Failing doctest:

    /// ```rust
    /// use cookie::{CookieJar, Cookie};
    ///
    /// let mut jar = CookieJar::new();
    ///
    /// jar.add_original(Cookie::new("name", "value"));
    /// jar.add_original(Cookie::new("second", "two"));
    ///
    /// jar.add(Cookie::new("new", "third"));
    /// jar.add(Cookie::new("another", "fourth"));
    /// jar.add(Cookie::new("yac", "fifth"));
    ///
    /// jar.remove(Cookie::named("name"));
    /// jar.remove(Cookie::named("another"));
    ///
    /// // There are three cookies in the jar: "second", "new", and "yac".
    /// # assert_eq!(jar.iter().count(), 3);
    /// for cookie in jar.iter() {
    ///     match cookie.name() {
    ///         "second" => assert_eq!(cookie.value(), "two"),
    ///         "new" => assert_eq!(cookie.value(), "third"),
    ///         "yac" => assert_eq!(cookie.value(), "fifth"),
    ///         _ => unreachable!("there are only three cookies in the jar")
    ///     }
    /// }
    /// ```

The assertion assert_eq!(jar.iter().count(), 3); is failing.

[alexcrichton]

This is an internal bug in cookie due to #57043 fixed by rwf2/cookie-rs#111, although I believe it was accidentally fixed.

This program:

extern crate cookie;

use std::collections::HashSet;

#[derive(Debug)]
struct A<'a>(&'a str, bool);

fn main() {
    let mut a = HashSet::new();
    a.insert(A("name", false));
    a.insert(A("second", false));

    let mut b = HashSet::new();
    b.replace(A("new", false));
    b.replace(A("another", false));
    b.replace(A("yac", false));

    b.replace(A("name", true));
    b.remove(&A("another", false));

    println!("{:?}", b.union(&a).collect::<Vec<_>>());
    println!("{:?}", b.iter().chain(a.difference(&b)).collect::<Vec<_>>());
}

impl<'a> std::hash::Hash for A<'a> {
    fn hash<H: std::hash::Hasher>(&self, h: &mut H) {
        self.0.hash(h);
    }
}

impl<'a> PartialEq for A<'a> {
    fn eq(&self, other: &A<'a>) -> bool {
        self.0 == other.0
    }
}

impl<'a> Eq for A<'a> {
}

has different output on stable/beta because of #57043. Both outputs are, however, correct. The cookie crate uses a data structure that only hashes one field (the name) but has other relevant information in the fields such as whether a cookie was removed and such. Depending on the order of iteration a cookie is either flagged as removed or filtered out from iteration.

tl;dr; everything is working as expected, this is a bug in the cookie crate that has already been fixed.