Function winnow::combinator::trace
source · pub fn trace<I: Stream, O, E>(
name: impl Display,
parser: impl Parser<I, O, E>
) -> impl Parser<I, O, E>
Expand description
Trace the execution of the parser
Note that Parser::context
also provides high level trace information.
See [tutorial][crate::_tutorial::chapter_8] for more details.
Example
use winnow::combinator::trace;
fn short_alpha<'s>(s: &mut &'s [u8]) -> PResult<&'s [u8], InputError<&'s [u8]>> {
trace("short_alpha",
take_while(3..=6, AsChar::is_alpha)
).parse_next(s)
}
assert_eq!(short_alpha.parse_peek(b"latin123"), Ok((&b"123"[..], &b"latin"[..])));
assert_eq!(short_alpha.parse_peek(b"lengthy"), Ok((&b"y"[..], &b"length"[..])));
assert_eq!(short_alpha.parse_peek(b"latin"), Ok((&b""[..], &b"latin"[..])));
assert_eq!(short_alpha.parse_peek(b"ed"), Err(ErrMode::Backtrack(InputError::new(&b"ed"[..], ErrorKind::Slice))));
assert_eq!(short_alpha.parse_peek(b"12345"), Err(ErrMode::Backtrack(InputError::new(&b"12345"[..], ErrorKind::Slice))));