bash-strings 0.1.0

Parse and emit bash's own quoted value forms: @Q words, array literals, declare -p bodies, and a word lexer over bash quoting.
Documentation 
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//! What a refusal says.

use std::fmt;

#[derive(Debug, Clone, PartialEq)]
pub struct ParseError {
    pub message: String,
    pub at: usize,
    pub snippet: String,
}

impl ParseError {
    pub fn new(input: &str, at: usize, message: impl Into<String>) -> Self {
        Self {
            message: message.into(),
            at,
            snippet: around(input, at),
        }
    }
}

impl fmt::Display for ParseError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
            "bash value parse error at byte {}: {} — near {:?}",
            self.at, self.message, self.snippet
        )
    }
}

impl std::error::Error for ParseError {}

/// The text around an offset, widened to character boundaries — so a snippet
/// is still a snippet when the input holds multi-byte characters.
fn around(input: &str, at: usize) -> String {
    let mut lo = at.saturating_sub(20).min(input.len());
    let mut hi = (at + 20).min(input.len());

    while !input.is_char_boundary(lo) {
        lo -= 1;
    }
    while !input.is_char_boundary(hi) {
        hi += 1;
    }
    input[lo..hi].to_string()
}