Changed behaviour of recognize from nom 7 to nom 8

[a-maier]

In nom 7 recognize returns the complete consumed input:

#!/usr/bin/env rust-script
//! ```cargo
//! [dependencies]
//! nom = "7"
//! ```

use nom::{
    IResult,
    character::complete::{alpha1, alphanumeric0},
    combinator::recognize,
};

fn main() {
    let id = "x11";

    use nom::sequence::tuple;
    fn var(input: &str) -> IResult<&str, &str> {
        recognize(tuple((alpha1, alphanumeric0)))(input)
    }
    assert_eq!(var(id), Ok(("", "x11")));
}

In nom 8 only the first character is returned:

#!/usr/bin/env rust-script
//! ```cargo
//! [dependencies]
//! nom = "8"
//! ```

use nom::{
    IResult,
    character::complete::{alpha1, alphanumeric0},
    combinator::recognize,
};

fn main() {
    let id = "x11";

    use nom::Parser;
    fn var(input: &str) -> IResult<&str, &str> {
        recognize((alpha1, alphanumeric0)).parse(input)
    }
    assert_eq!(var(id), Ok(("", "x")));
}

Is this intended? Is there a way to get back the old behaviour?

[Tahaa-Dev]

No, it isn't intended, in documentation and my usage of nom v8.0.0, it returns all consumed input, when changing from alphanumeric0 to alphanumeric1 in your second snippet, it works, and using digit0 also doesn't work while using digit1 does, I don't know the reason behind this weird behavior

and when switching from alpha1 to alpha0 doesn't change anything, I'll read the source

[Tahaa-Dev]

I read the source, the issue seems to come from the recognize function, I can't really solve it but running:

use nom::{
    IResult,
    character::complete::{alpha1, alphanumeric0},
};

fn main() {
    let id = "x11";

    use nom::Parser;
    fn var(input: &str) -> IResult<&str, &str> {
        (alpha1, alphanumeric0).parse(input)
    }
    assert_eq!(var(id), Ok(("", ("x", "11"))));
}

actually works, I don't know what's wrong with recognize, I'll try to figure it out and open a PR

[Tahaa-Dev]

It was fixed already, issue #1808 addressed it and fixed in PR #1811, it just hasn't been published to crates.io yet, sorry for not checking first before commenting the first two comments

[a-maier]

Thanks and sorry, I should have realized that this bug had already been reported.