Failure with Valid Input about rust-onig HOT 1 CLOSED

I can reproduce this:

use onig::Regex;

fn main() {
    test("Greater|GreaterOrEqual");
    test("GreaterOrEqual|Greater");
}

fn test(regex_string: &str) {
    let re = Regex::new(regex_string).unwrap();
    println!("Regex: {regex_string}");
    check(&re, "Greater");
    check(&re, "GreaterOrEqual");
}

fn check(regex: &Regex, input: &str) {
    let matched = regex.is_match(input);
    println!("Input: {input} = {matched}");
}

This seems to be caused by the way that is_match works. We first match the regex against the text, and then check
that the whole text was matched. In this case the order of the alternation changes what Oniguruma matches. If the
GreaterOrEqual is first then we match the longer item. if Greater is first then we only match that. This then means
that the expression hasn't matched the whole input text causing the behaviour you're seeing.

There's an option for Oniguruma which should allow us to force it to choose the longest match, but setting it either
with (?L) in the pattern or via RegexOptions::::REGEX_OPTION_FIND_LONGEST doesn't seem to affect the
outcome.

from rust-onig.