support named capture groups

[jtmoon79]

Named capture groups allow accessing a capture by a str.

using regex

From the regex docs

use regex::Regex;

let re = Regex::new(r"Homer (?<middle>.)\. Simpson").unwrap();
let hay = "Homer J. Simpson";
let Some(caps) = re.captures(hay) else { return };
assert_eq!("J", &caps["middle"]);

Notice the (?<middle>.) with syntax ?<middle> to declare that capture group name middle.

using ere

Using ere, this indexed capture group compiles

use ::ere::{compile_regex, Regex};

const MY_REGEX1: Regex<2> = compile_regex!(r"Homer (.)\. Simpson");

and this named capture group fails

use ::ere::{compile_regex, Regex};

const MY_REGEX1: Regex<2> = compile_regex!(r"Homer (?<middle>.)\. Simpson");

with

An atom was expected but was invalid due to being a special character: `)`

Feature Request

Can ere add support for named capture groups?
I'd love to use them in my project.
Cool project! 🙂

[2kai2kai2]

My thoughts on this is that instead of writing in-regex names (which don't exist in POSIX EREs), I could add it to the (currently unstable) struct-based syntax.

Something like this:

#![cfg(feature = "unstable-attr-regex")]

use ere::regex;

#[regex(r"Homer (.)\. Simpson")]
struct MyRegex<'a> {
    whole: &'a str, // capture group 0 is always the entire match
    middle: &'a str, // capture group 1
}

let Some(captures) = MyRegex::exec("Homer J. Simpson") else {
    panic!("no match");
};
assert_eq!(captures.middle, "J");
assert!(core::ptr::eq(captures.capture1(), captures.middle)); // maybe generate functions for getting by index, idk

[jtmoon79]

My thoughts on this is that instead of writing in-regex names (which don't exist in POSIX EREs), I could add it to the (currently unstable) struct-based syntax.

Any form of support would be useful. That struct form seems slick.

However it would be cool if I could take existing regular expressions that were using regex with the embedded capture group name syntax, and swap in ere. But I have no sense of the difficulty of implementation for you.

Thanks for considering this 🙂