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|
#![doc(html_root_url = "https://docs.rs/abnf_to_pest/0.1.1")]
//! A tiny crate that helps convert ABNF grammars to [pest][pest].
//!
//! Example usage:
//! ```
//! let abnf_path = "src/grammar.abnf";
//! let pest_path = "src/grammar.pest";
//!
//! let mut file = File::open(abnf_path)?;
//! let mut data = Vec::new();
//! file.read_to_end(&mut data)?;
//! data.push('\n' as u8);
//!
//! let mut rules = abnf_to_pest::parse_abnf(&data)?;
//! rules.remove("some_inconvenient_rule");
//!
//! let mut file = File::create(pest_path)?;
//! writeln!(&mut file, "{}", render_rules_to_pest(rules).pretty(80))?;
//! ```
//!
//! [pest]: https://pest.rs
use abnf::abnf::Rule;
pub use abnf::abnf::{
Alternation, Concatenation, Element, Range, Repeat, Repetition,
};
use itertools::Itertools;
use pretty::{BoxDoc, Doc};
use indexmap::map::IndexMap;
trait Pretty {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>>;
}
impl Pretty for Alternation {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
Doc::intersperse(
self.concatenations
.iter()
.map(|x| x.pretty().nest(2).group()),
Doc::space().append(Doc::text("| ")),
)
}
}
impl Pretty for Concatenation {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
Doc::intersperse(
self.repetitions.iter().map(Repetition::pretty),
Doc::space().append(Doc::text("~ ")),
)
}
}
impl Pretty for Repetition {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
self.element.pretty().append(
self.repeat
.as_ref()
.map(Repeat::pretty)
.unwrap_or_else(Doc::nil),
)
}
}
impl Pretty for Repeat {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
Doc::text(match (self.min.unwrap_or(0), self.max) {
(0, None) => "*".into(),
(1, None) => "+".into(),
(0, Some(1)) => "?".into(),
(min, None) => format!("{{{},}}", min),
(min, Some(max)) if min == max => format!("{{{}}}", min),
(min, Some(max)) => format!("{{{},{}}}", min, max),
})
}
}
impl Pretty for Element {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
use abnf::abnf::Element::*;
match self {
Rulename(s) => Doc::text(escape_rulename(s)),
Group(g) => Doc::text("(")
.append((g.alternation).pretty().nest(4).group())
.append(Doc::text(")")),
Option(o) => Doc::text("(")
.append((o.alternation).pretty().nest(4).group())
.append(Doc::text(")?")),
CharVal(s) => Doc::text(format!(
"^\"{}\"",
s.replace("\"", "\\\"").replace("\\", "\\\\")
)),
NumVal(r) => r.pretty(),
ProseVal(_) => unimplemented!(),
}
}
}
impl Pretty for Range {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
use abnf::abnf::Range::*;
Doc::text(match self {
Range(x, y) => {
format!("'{}'..'{}'", format_char(*x), format_char(*y))
}
OneOf(v) => {
format!("\"{}\"", v.iter().map(|x| format_char(*x)).join(""))
}
})
}
}
/// Escape the rule name to be a valid Rust identifier.
///
/// Replaces e.g. `if` with `if_`, and `rule-name` with `rule_name`.
/// Also changes `whitespace` to `whitespace_` because of https://github.com/pest-parser/pest/pull/374
pub fn escape_rulename(x: &str) -> String {
let x = x.replace("-", "_");
if x == "if"
|| x == "else"
|| x == "as"
|| x == "let"
|| x == "in"
|| x == "fn"
// TODO: remove when https://github.com/pest-parser/pest/pull/375 gets into a release
|| x == "whitespace"
{
x + "_"
} else {
x.clone()
}
}
fn format_char(x: u32) -> String {
if x <= u32::from(u8::max_value()) {
let x: u8 = x as u8;
if x.is_ascii_graphic() {
let x: char = x as char;
if x != '"' && x != '\'' && x != '\\' {
return x.to_string();
}
}
}
format!("\\u{{{:02X}}}", x)
}
/// Allow control over some of the pest properties of the outputted rule
pub struct PestyRule {
pub silent: bool,
pub elements: Alternation,
}
impl Pretty for (String, PestyRule) {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
Doc::nil()
.append(Doc::text(self.0.clone()))
.append(Doc::text(" = "))
.append(Doc::text(if self.1.silent { "_" } else { "" }))
.append(Doc::text("{"))
.append(Doc::space().append(self.1.elements.pretty()).nest(2))
.append(Doc::space())
.append(Doc::text("}"))
.group()
}
}
/// Parse an abnf file. Returns a map of rules.
pub fn parse_abnf(
data: &[u8],
) -> Result<IndexMap<String, PestyRule>, std::io::Error> {
let make_err =
|e| std::io::Error::new(std::io::ErrorKind::Other, format!("{}", e));
let rules: Vec<Rule> =
abnf::abnf::rulelist_comp(&data).map_err(make_err)?.1;
Ok(rules
.into_iter()
.map(|rule| {
let name = escape_rulename(&rule.name);
(
name.clone(),
PestyRule {
silent: false,
elements: rule.elements.clone(),
},
)
})
.collect())
}
pub fn render_rules_to_pest<I>(
rules: I,
) -> Doc<'static, BoxDoc<'static, ()>, ()>
where
I: IntoIterator<Item = (String, PestyRule)>,
{
let pretty_rules = rules.into_iter().map(|x| x.pretty());
let doc: Doc<_> = Doc::intersperse(pretty_rules, Doc::newline());
doc
}
|
