Unexpected Bang Since 0.23.1

[JojiiOfficial]

The following file can't be parsed since 0.23.1 as it throws an UnexpectedBang(69) when parsing with the given example code. Simply ignoring the error causes the given example code not to parse anything at all. Version 0.22.0 worked fine
JMdict.zip
This is just a trimmed file of the JMdict file to demonstrate the issue. You can find the original file here.

Working v0.22.0 Code:

use quick_xml::{events::Event, Reader};
use std::{fs::File, io::BufReader};

fn main() {
    let mut reader = Reader::from_reader(BufReader::new(File::open("./JMdict_short").unwrap()));
    reader.trim_text(true);
    let mut buf = vec![];

    loop {
        match reader.read_event(&mut buf) {
            Ok(Event::Start(ref e)) => {
                if let b"entry" = e.name() {
                    println!("{}", std::str::from_utf8(e.name()).unwrap());
                }
            }

            Ok(Event::Eof) => break,

            Err(e) => {
                panic!("{e:?}");
            }

            _ => (),
        }
    }
}

Broken v0.28.1 Code (same code, just migrated):

use quick_xml::{events::Event, Reader};
use std::{fs::File, io::BufReader};

fn main() {
    let mut reader = Reader::from_reader(BufReader::new(File::open("./JMdict_short").unwrap()));
    reader.trim_text(true);
    let mut buf = vec![];

    loop {
        match reader.read_event_into(&mut buf) {
            Ok(Event::Start(ref e)) => {
                if let b"entry" = e.name().0 {
                    println!("{}", std::str::from_utf8(e.name().0).unwrap());
                }
            }

            Ok(Event::Eof) => break,

            Err(e) => {
                panic!("{e:?}");
            }

            _ => (),
        }
    }
}

[Mingun]

It seems that this bug is happened when <!DOCTYPE > content contains at least two inner <!x> elements and BufReader buffer too small to hold them both. The minimal reproduction case that I've found is

/// Regression test for https://github.com/tafia/quick-xml/issues/590
#[test]
fn issue590() {
    let mut reader = Reader::from_reader(BufReader::with_capacity(
        16,
        &b"<!DOCTYPE t [<!1><!2>]>"[..],
        // 0      7       ^15    ^23
        //[                ] = capacity
    ));
    let mut buf = vec![];
    loop {
        match reader.read_event_into(&mut buf).unwrap() {
            Event::Eof => break,
            _ => (),
        }
    }
}

[JojiiOfficial]

Interesting though that this is dependent on the buffer which should be transparent to the xml reader. But indeed increasing the buffer size fixes the issue.

[Mingun]

Duplicate of #533