fancy-regex 0.3.3

An implementation of regexes, supporting a relatively rich set of features, including backreferences and look-around.
Documentation 
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use fancy_regex::{Captures, Match, Result};

mod common;

#[test]
fn captures_fancy() {
    let captures = captures(r"\s*(\w+)(?=\.)", "foo bar.");
    assert_eq!(captures.len(), 2);
    assert_match(captures.get(0), " bar", 3, 7);
    assert_match(captures.get(1), "bar", 4, 7);
    assert!(captures.get(2).is_none());
}

#[test]
fn captures_fancy_unmatched_group() {
    let captures = captures(r"(\w+)(?=\.)|(\w+)(?=!)", "foo! bar.");
    assert_eq!(captures.len(), 3);
    assert_match(captures.get(0), "foo", 0, 3);
    assert!(captures.get(1).is_none());
    assert_match(captures.get(2), "foo", 0, 3);
}

#[test]
fn captures_after_lookbehind() {
    let captures = captures(
        r"\s*(?<=[() ])(@\w+)(\([^)]*\))?\s*",
        " @another(foo bar)   ",
    );
    assert_match(captures.get(1), "@another", 1, 9);
    assert_match(captures.get(2), "(foo bar)", 9, 18);
}

#[test]
fn captures_from_pos() {
    let text = "11 21 33";

    let regex = common::regex(r"(\d)\d");
    let captures = assert_captures(regex.captures_from_pos(text, 3));
    assert_eq!(captures.len(), 2);
    assert_match(captures.get(0), "21", 3, 5);
    assert_match(captures.get(1), "2", 3, 4);
    let matches: Vec<_> = captures.iter().collect();
    assert_eq!(matches.len(), 2);
    assert_match(matches[0], "21", 3, 5);
    assert_match(matches[1], "2", 3, 4);

    let regex = common::regex(r"(\d+)\1");
    let captures = assert_captures(regex.captures_from_pos(text, 3));
    assert_eq!(captures.len(), 2);
    assert_match(captures.get(0), "33", 6, 8);
    assert_match(captures.get(1), "3", 6, 7);
    let matches: Vec<_> = captures.iter().collect();
    assert_eq!(matches.len(), 2);
    assert_match(matches[0], "33", 6, 8);
    assert_match(matches[1], "3", 6, 7);
}

#[test]
fn captures_from_pos_looking_left() {
    let regex = common::regex(r"\b(\w)");

    // This should *not* match because `\b` doesn't match between a and x
    let result = regex.captures_from_pos("ax", 1).unwrap();
    assert!(result.is_none());

    let captures = assert_captures(regex.captures_from_pos(".x", 1));
    assert_eq!(captures.len(), 2);
    assert_match(captures.get(0), "x", 1, 2);
    assert_match(captures.get(1), "x", 1, 2);
}

fn captures<'a>(re: &str, text: &'a str) -> Captures<'a> {
    let regex = common::regex(re);
    let result = regex.captures(text);
    assert_captures(result)
}

fn assert_captures(result: Result<Option<Captures<'_>>>) -> Captures<'_> {
    assert!(
        result.is_ok(),
        "Expected captures to succeed, but was {:?}",
        result
    );
    let captures = result.unwrap();
    assert!(
        captures.is_some(),
        "Expected captures, but was {:?}",
        captures
    );
    captures.unwrap()
}

fn assert_match(m: Option<Match<'_>>, expected_text: &str, start: usize, end: usize) {
    assert!(m.is_some(), "Expected match, but was {:?}", m);
    let m = m.unwrap();
    assert_eq!(m.as_str(), expected_text);
    assert_eq!(m.start(), start);
    assert_eq!(m.end(), end);
}