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//! This is a parser for JSON.
//! Run it with the following command:
//! cargo run --example json -- examples/sample.json
use ariadne::{Color, Fmt, Label, Report, ReportKind, Source};
use chumsky::prelude::*;
use std::{collections::HashMap, env, fs};
#[derive(Clone, Debug)]
enum Json {
Invalid,
Null,
Bool(bool),
Str(String),
Num(f64),
Array(Vec<Json>),
Object(HashMap<String, Json>),
}
fn parser() -> impl Parser<char, Json, Error = Simple<char>> {
recursive(|value| {
let frac = just('.').chain(text::digits(10));
let exp = just('e')
.or(just('E'))
.chain(just('+').or(just('-')).or_not())
.chain::<char, _, _>(text::digits(10));
let number = just('-')
.or_not()
.chain::<char, _, _>(text::int(10))
.chain::<char, _, _>(frac.or_not().flatten())
.chain::<char, _, _>(exp.or_not().flatten())
.collect::<String>()
.from_str()
.unwrapped()
.labelled("number");
let escape = just('\\').ignore_then(
just('\\')
.or(just('/'))
.or(just('"'))
.or(just('b').to('\x08'))
.or(just('f').to('\x0C'))
.or(just('n').to('\n'))
.or(just('r').to('\r'))
.or(just('t').to('\t'))
.or(just('u').ignore_then(
filter(|c: &char| c.is_digit(16))
.repeated()
.exactly(4)
.collect::<String>()
.validate(|digits, span, emit| {
char::from_u32(u32::from_str_radix(&digits, 16).unwrap())
.unwrap_or_else(|| {
emit(Simple::custom(span, "invalid unicode character"));
'\u{FFFD}' // unicode replacement character
})
}),
)),
);
let string = just('"')
.ignore_then(filter(|c| *c != '\\' && *c != '"').or(escape).repeated())
.then_ignore(just('"'))
.collect::<String>()
.labelled("string");
let array = value
.clone()
.chain(just(',').ignore_then(value.clone()).repeated())
.or_not()
.flatten()
.delimited_by(just('['), just(']'))
.map(Json::Array)
.labelled("array");
let member = string.clone().then_ignore(just(':').padded()).then(value);
let object = member
.clone()
.chain(just(',').padded().ignore_then(member).repeated())
.or_not()
.flatten()
.padded()
.delimited_by(just('{'), just('}'))
.collect::<HashMap<String, Json>>()
.map(Json::Object)
.labelled("object");
just("null")
.to(Json::Null)
.labelled("null")
.or(just("true").to(Json::Bool(true)).labelled("true"))
.or(just("false").to(Json::Bool(false)).labelled("false"))
.or(number.map(Json::Num))
.or(string.map(Json::Str))
.or(array)
.or(object)
.recover_with(nested_delimiters('{', '}', [('[', ']')], |_| Json::Invalid))
.recover_with(nested_delimiters('[', ']', [('{', '}')], |_| Json::Invalid))
.recover_with(skip_then_retry_until(['}', ']']))
.padded()
})
.then_ignore(end().recover_with(skip_then_retry_until([])))
}
fn main() {
let src = fs::read_to_string(env::args().nth(1).expect("Expected file argument"))
.expect("Failed to read file");
let (json, errs) = parser().parse_recovery(src.trim());
println!("{:#?}", json);
errs.into_iter().for_each(|e| {
let msg = if let chumsky::error::SimpleReason::Custom(msg) = e.reason() {
msg.clone()
} else {
format!(
"{}{}, expected {}",
if e.found().is_some() {
"Unexpected token"
} else {
"Unexpected end of input"
},
if let Some(label) = e.label() {
format!(" while parsing {}", label)
} else {
String::new()
},
if e.expected().len() == 0 {
"something else".to_string()
} else {
e.expected()
.map(|expected| match expected {
Some(expected) => expected.to_string(),
None => "end of input".to_string(),
})
.collect::<Vec<_>>()
.join(", ")
},
)
};
let report = Report::build(ReportKind::Error, (), e.span().start)
.with_code(3)
.with_message(msg)
.with_label(
Label::new(e.span())
.with_message(match e.reason() {
chumsky::error::SimpleReason::Custom(msg) => msg.clone(),
_ => format!(
"Unexpected {}",
e.found()
.map(|c| format!("token {}", c.fg(Color::Red)))
.unwrap_or_else(|| "end of input".to_string())
),
})
.with_color(Color::Red),
);
let report = match e.reason() {
chumsky::error::SimpleReason::Unclosed { span, delimiter } => report.with_label(
Label::new(span.clone())
.with_message(format!(
"Unclosed delimiter {}",
delimiter.fg(Color::Yellow)
))
.with_color(Color::Yellow),
),
chumsky::error::SimpleReason::Unexpected => report,
chumsky::error::SimpleReason::Custom(_) => report,
};
report.finish().print(Source::from(&src)).unwrap();
});
}
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