Node::set_content failing (and clearing content) without returning Err

[insiderscore-jeff]

This may be a bug in libxml itself, but if you call set_content with an ampersand (&) that isn't & it treats it at an entity, and if that entity is unknown/invalid, it will print out "error: unterminated entity reference" on stderr, and will set the node content to blank string. The concerning thing is that set_content is not returning Err.

libxml = "0.3"

use libxml::tree::*;


fn main() {
    // induce set content bug in set_content
    let mut d = Document::new().unwrap();
    let mut n = Node::new("span", None, &d).unwrap();

    n.set_content("Testing").unwrap();
    let s = n.get_content();
    assert_eq!(s, "Testing");

    n.set_content("Testing & Breaking").unwrap();
    let s = n.get_content();
    assert_eq!(s, "Testing & Breaking");
}

output:

 Running `target/debug/ctest`
error : unterminated entity reference        Breaking
thread 'main' panicked at src/main.rs:15:5:
assertion `left == right` failed
  left: ""
 right: "Testing & Breaking"

[dginev]

I wonder what is the most user-friendly way to improve this behavior. It's not quite a bug, since you are not supposed to use literal ampersands in XML. Reframing to & passes your test:

n.set_content("Testing & Breaking").unwrap();
let s = n.get_content();
assert_eq!(s, "Testing & Breaking");

That said, it is clearly a gotcha.

[insiderscore-jeff]

I would think having it return Err (and not set the content to blank) would be the most ideal thing, but I also realize it could absolutely be a "feature" in libxml itself (I've run into a couple things like that over the years with libxml)

Locally I'm probably going to use a wrapper to set_content to replace & with & and wait for situation where the content has & already in it :)

[insiderscore-jeff]

oh, and if Node is a text node, this works fine.

    let mut d = Document::new().unwrap();
    let mut n = Node::new_text("Testing",  &d).unwrap();

    n.set_content("Testing").unwrap();
    let s = n.get_content();
    assert_eq!(s, "Testing");

    n.set_content("Testing & Breaking").unwrap();
    let s = n.get_content();
    assert_eq!(s, "Testing & Breaking");

[insiderscore-jeff]

sorry for the deluge of comments, but the route that lead me to this can be widdled down to:

    let mut n = Node::new("span", None, &d).unwrap();

    n.set_content("Testing & Breaking").unwrap();
    let s = n.get_content();
    assert_eq!(s, "Testing & Breaking");

    n.set_content(&s).unwrap();
    let s2 = n.get_content();
    assert_eq!(s, s2);

error : unterminated entity reference        Breaking
thread 'main' panicked at src/main.rs:15:5:
assertion `left == right` failed
  left: "Testing & Breaking"
 right: ""

line 15 being the s, s2 assert_eq