marser 0.1.2

Parser combinator toolkit with matcher-level backtracking and rich error reporting.
Documentation 
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//! Enrich [`crate::error::FurthestFailError`] from `happy_matcher` using a small [`crate::parser::Parser`] callback.
//!
//! On [`crate::error::MatcherRunError::FurthestFail`], this combinator runs `error_parser` at the failure cursor to obtain a
//! callback that mutates the error. [`crate::error::MatcherRunError::RetryRerunNeeded`] is forwarded unchanged so the outer
//! capture retry path can rewind and rerun with a recovery **non-memoizing backtracking runner**
//! without nested `error_parser` work.

use std::fmt::Display;

use crate::{
    context::ParserContext,
    error::{FurthestFailError, MatcherRunError, error_handler::ErrorHandler},
    input::{Input, InputStream},
    matcher::{MatchRunner, Matcher, MatcherCombinator},
    parser::{Parser, ParserCombinator, internal::ParserImpl},
};

/// On [`Err`] from the inner matcher, runs `error_parser` to obtain a callback that mutates the error.
#[derive(Clone, Debug)]
pub struct ErrorContextualizer<Happy, Pars> {
    happy: Happy,
    error_parser: Pars,
}

impl<Matcher, Pars> MatcherCombinator for ErrorContextualizer<Matcher, Pars> where
    Matcher: MatcherCombinator
{
}
impl<Happy, Pars> ParserCombinator for ErrorContextualizer<Happy, Pars> where Happy: ParserCombinator
{}

impl<Matcher, Pars> ErrorContextualizer<Matcher, Pars> {
    /// See [`crate::matcher::MatcherCombinator::add_error_info`].
    pub fn new(happy: Matcher, error_parser: Pars) -> Self {
        Self {
            happy,
            error_parser,
        }
    }
}

//TODO: ensure that Pars cannot error with trait CanNotError
impl<'src, Inp: Input<'src>, Happy, Pars, MRes> super::internal::MatcherImpl<'src, Inp, MRes>
    for ErrorContextualizer<Happy, Pars>
where
    Happy: Matcher<'src, Inp, MRes>,
    Pars: Parser<'src, Inp, Output = Box<dyn Fn(&mut FurthestFailError)>>,
    Inp: Input<'src>,
{
    const CAN_MATCH_DIRECTLY: bool = Happy::CAN_MATCH_DIRECTLY;
    const HAS_PROPERTY: bool = Happy::HAS_PROPERTY;
    const CAN_FAIL: bool = Happy::CAN_FAIL;

    #[inline]
    fn match_with_runner<'a, Runner>(
        &'a self,
        runner: &mut Runner,
        error_handler: &mut impl ErrorHandler,
        input: &mut InputStream<'src, Inp>,
    ) -> Result<bool, MatcherRunError>
    where
        Runner: MatchRunner<'a, 'src, Inp, MRes = MRes>,
        'src: 'a,
    {
        let start_pos = input.get_pos();
        match runner.run_match(&self.happy, error_handler, input) {
            Ok(true) => Ok(true),
            Ok(false) => Ok(false),
            Err(MatcherRunError::RetryRerunNeeded) => Err(MatcherRunError::RetryRerunNeeded),
            Err(MatcherRunError::FurthestFail(mut e)) => {
                let resume_pos = input.get_pos();
                input.set_pos(start_pos.clone());
                if let Ok(Some(f)) =
                    self.error_parser
                        .parse(runner.get_parser_context(), error_handler, input)
                {
                    f(&mut e);
                }
                input.set_pos(resume_pos);
                Err(MatcherRunError::FurthestFail(e))
            }
        }
    }

    #[inline]
    fn maybe_label(&self) -> Option<Box<dyn Display>> {
        self.happy.maybe_label()
    }
}

// impl Parser
impl<'src, Inp: Input<'src>, Happy, Pars> ParserImpl<'src, Inp> for ErrorContextualizer<Happy, Pars>
where
    Happy: Parser<'src, Inp>,
    Pars: Parser<'src, Inp, Output = Box<dyn Fn(&mut FurthestFailError)>>,
    Inp: Input<'src>,
{
    type Output = Happy::Output;
    const CAN_FAIL: bool = Happy::CAN_FAIL;

    #[inline]
    fn parse(
        &self,
        context: &mut ParserContext<'src>,
        error_handler: &mut impl ErrorHandler,
        input: &mut InputStream<'src, Inp>,
    ) -> Result<Option<Self::Output>, MatcherRunError> {
        let start_pos = input.get_pos();
        match self.happy.parse(context, error_handler, input) {
            Ok(Some(output)) => Ok(Some(output)),
            Ok(None) => Ok(None),
            Err(MatcherRunError::RetryRerunNeeded) => Err(MatcherRunError::RetryRerunNeeded),
            Err(MatcherRunError::FurthestFail(mut e)) => {
                let resume_pos = input.get_pos();
                input.set_pos(start_pos);
                if let Ok(Some(f)) = self.error_parser.parse(context, error_handler, input) {
                    f(&mut e);
                }
                input.set_pos(resume_pos);
                Err(MatcherRunError::FurthestFail(e))
            }
        }
    }

    #[inline]
    fn maybe_label(&self) -> Option<Box<dyn Display>> {
        self.happy.maybe_label()
    }
}