snacks 0.1.11

more nom parser-combinators
Documentation 
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use nom::error::{ErrorKind, ParseError};
use nom::{IResult, Input, Parser};

/// Runs the item parser interlaced by the separator parser.
///
/// The main difference to the [`nom::multi::separated_list0`] parser is,
/// that this parser returns the recognized string without allocating a list.
///
/// If the item parser does not complete successfully at least one time,
/// an empty list is returned.
///
/// ```rust
/// use nom::character::complete::{alphanumeric1, char};
/// use snacks::recognize_separated0;
///
/// let input = "comma,separated,words other";
/// let result = recognize_separated0::<_, _, _, nom::error::Error<_>>(alphanumeric1, char(','))(input);
/// assert_eq!(Ok((" other", "comma,separated,words")), result);
/// ```
pub fn recognize_separated0<I, Separator, Item, Error>(
    item: Item,
    separator: Separator,
) -> impl FnMut(I) -> IResult<I, I>
where
    I: Input + Copy,
    Separator: Parser<I, Error = Error>,
    Item: Parser<I, Error = Error> + Copy,
    Error: ParseError<I>,
{
    let mut item = item;
    let mut next_item = (separator, item);
    move |start| {
        let Ok((mut input, _)) = item.parse(start) else {
            return Ok(start.take_split(0));
        };
        loop {
            let Ok((remaining, _)) = next_item.parse(input) else {
                return Ok(start.take_split(start.input_len() - input.input_len()));
            };
            input = remaining;
        }
    }
}

/// Runs the item parser interlaced by the separator parser.
///
/// The main difference to the [`nom::multi::separated_list1`] parser from nom is,
/// that this parser returns the recognized string without allocating a list.
///
/// If the item parser does not complete successfully at least one time,
/// an error is returned.
///
/// ```rust
/// use nom::character::complete::{alphanumeric1, char};
/// use snacks::recognize_separated1;
///
/// let input = "comma,separated,words other";
/// let result = recognize_separated1::<_, _, _, nom::error::Error<_>>(alphanumeric1, char(','))(input);
/// assert_eq!(Ok((" other", "comma,separated,words")), result);
/// ```
pub fn recognize_separated1<I, Separator, Item, Error>(
    item: Item,
    separator: Separator,
) -> impl FnMut(I) -> IResult<I, I>
where
    I: Input + Copy,
    Separator: Parser<I, Error = Error>,
    Item: Parser<I, Error = Error> + Copy,
    Error: ParseError<I>,
{
    let mut item = item;
    let mut next_item = (separator, item);
    move |start| {
        let Ok((mut input, _)) = item.parse(start) else {
            return Err(nom::Err::Error(nom::error::Error::new(
                start,
                ErrorKind::SeparatedList,
            )));
        };
        loop {
            let Ok((remaining, _)) = next_item.parse(input) else {
                return Ok(start.take_split(start.input_len() - input.input_len()));
            };
            input = remaining;
        }
    }
}

#[cfg(test)]
mod tests {
    use nom::bytes::complete::is_a;
    use nom::character::complete::alphanumeric1;

    use super::*;

    #[test]
    fn can_recognize_empty_separated0() {
        let input = "";
        let result = recognize_separated0::<_, _, _, nom::error::Error<_>>(
            alphanumeric1,
            is_a(",; "),
        )(input);
        assert_eq!(Ok(("", "")), result);
    }

    #[test]
    fn can_recognize_comma_separated_elements_separated0() {
        let input = "all, comma, separated-elements";
        let result = recognize_separated0::<_, _, _, nom::error::Error<_>>(
            alphanumeric1,
            is_a(",; "),
        )(input);
        assert_eq!(Ok(("-elements", "all, comma, separated")), result);
    }

    #[test]
    fn can_recognize_empty_separated1() {
        let input = "";
        let result = recognize_separated1::<_, _, _, nom::error::Error<_>>(
            alphanumeric1,
            is_a(",; "),
        )(input);
        assert!(result.is_err());
    }

    #[test]
    fn can_recognize_comma_separated_elements_separated1() {
        let input = "all, comma, separated-elements";
        let result = recognize_separated1::<_, _, _, nom::error::Error<_>>(
            alphanumeric1,
            is_a(",; "),
        )(input);
        assert_eq!(Ok(("-elements", "all, comma, separated")), result);
    }
}