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#![doc(html_root_url = "https://docs.rs/abnf_to_pest/0.5.0")]
//! 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::types::{Node, NumVal, Repeat, Rule};
use indexmap::map::IndexMap;
use itertools::Itertools;
use pretty::{BoxDoc, Doc};
trait Pretty {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>>;
}
impl Pretty for Node {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
use Node::*;
match self {
Alternation(nodes) => Doc::intersperse(
nodes.iter().map(|x| x.pretty().nest(2).group()),
Doc::space().append(Doc::text("| ")),
),
Concatenation(nodes) => Doc::intersperse(
nodes.iter().map(|x| x.pretty()),
Doc::space().append(Doc::text("~ ")),
),
Repetition(rep) => {
rep.get_node().pretty().append(rep.get_repeat().pretty())
}
Rulename(s) => Doc::text(escape_rulename(s)),
Group(n) => Doc::text("(")
.append(n.pretty().nest(4).group())
.append(Doc::text(")")),
Optional(n) => Doc::text("(")
.append(n.pretty().nest(4).group())
.append(Doc::text(")?")),
CharVal(s) => Doc::text(format!(
"^\"{}\"",
s.replace("\"", "\\\"").replace("\\", "\\\\")
)),
NumVal(r) => r.pretty(),
ProseVal(_) => unimplemented!(),
}
}
}
impl Pretty for Repeat {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
Doc::text(match (self.get_min().unwrap_or(0), self.get_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 NumVal {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
use NumVal::*;
Doc::text(match self {
Range(x, y) => {
format!("'{}'..'{}'", format_char(*x), format_char(*y))
}
Terminal(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
/// Also changes `Some` and `None` to `Some_` and `None_`, because it was such a pain to work around.
pub fn escape_rulename(x: &str) -> String {
let x = x.replace("-", "_");
if x == "if"
|| x == "else"
|| x == "as"
|| x == "let"
|| x == "in"
|| x == "fn"
// Not required but such a pain
|| x == "Some"
|| x == "None"
// TODO: remove when https://github.com/pest-parser/pest/pull/375 gets into a release
|| x == "whitespace"
{
x + "_"
} else {
x
}
}
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
#[derive(Debug, Clone)]
pub struct PestyRule {
pub silent: bool,
pub node: Node,
}
impl Pretty for (String, PestyRule) {
fn pretty(&self) -> Doc<'static, BoxDoc<'static, ()>> {
let (name, rule) = self;
Doc::nil()
.append(Doc::text(name.clone()))
.append(Doc::text(" = "))
.append(Doc::text(if rule.silent { "_" } else { "" }))
.append(Doc::text("{"))
.append(Doc::space().append(rule.node.pretty()).nest(2))
.append(Doc::space())
.append(Doc::text("}"))
.group()
}
}
/// Parse an abnf file. Returns a map of rules.
pub fn parse_abnf(
data: &str,
) -> 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::rulelist(data).map_err(make_err)?;
Ok(rules
.into_iter()
.map(|rule| {
(
escape_rulename(rule.get_name()),
PestyRule {
silent: false,
node: rule.get_node().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
}
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