pest_ascii_tree/lib.rs
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//! # pest_ascii_tree
//!
//! This is a small helper crate useful for quickly debugging your pest
//! grammar.
//! The rules found by parsing the file are formated into an
//! [`ascii_tree`].
//!
//! It is useful, you you want to quickly debug your grammar without
//! having to write specialized code for handling the `Pairs` iterator
//! returned by your pest parser.
//!
//! Example, for whan an output might look like.
//! <pre>
//! expr
//! ├─ expr
//! │ ├─ val "u"
//! │ ├─ op "+"
//! │ └─ expr
//! │ ├─ val "v"
//! │ ├─ op "+"
//! │ └─ val "w"
//! ├─ op "+"
//! ├─ expr
//! │ ├─ val "x"
//! │ ├─ op "+"
//! │ └─ val "y"
//! ├─ op "+"
//! └─ val "z"
//! </pre>
//!
//! Please, that the `EOI` rule is skipped.
//!
//! [`ascii_tree`]: ../ascii_tree/index.html
extern crate ascii_tree;
extern crate escape_string;
extern crate pest;
#[macro_use]
extern crate pest_derive;
use pest::{error::Error, iterators::Pairs};
fn into_ascii_tree_nodes<R>(mut pairs: Pairs<R>) -> Vec<ascii_tree::Tree>
where
R: pest::RuleType,
{
let mut vec = Vec::new();
while let Some(pair) = pairs.next() {
let pair_content = pair.as_span().as_str().trim();
let pair_rule = pair.as_rule();
let inner_pairs = into_ascii_tree_nodes(pair.into_inner());
let rule_name = format!("{:?}", pair_rule);
if rule_name == "EOI" {
continue;
}
let node;
if inner_pairs.is_empty() {
let leaf = format!(
"{:?} \"{}\"",
pair_rule,
escape_string::escape(pair_content)
);
node = ascii_tree::Tree::Leaf(vec![leaf]);
} else {
node = ascii_tree::Tree::Node(rule_name, inner_pairs);
}
vec.push(node);
}
vec
}
/// Formats the parsing result by pest into an ascii_tree
/// into a [`String`].
///
/// # Error
/// If the internal call to [`ascii_tree::write_tree`] failed, the error
/// variant is passed to the caller.
///
/// # Examples
/// ```ignore
/// let result = pest_ascii_tree::into_ascii_tree(
/// ExpressionParser::parse(Rule::expr, "(u + (v + w)) + (x + y) + z")?)?;
/// assert_eq!(
/// result,
/// String::new()
/// + " expr\n"
/// + " ├─ expr\n"
/// + " │ ├─ val \"u\"\n"
/// + " │ ├─ op \"+\"\n"
/// + " │ └─ expr\n"
/// + " │ ├─ val \"v\"\n"
/// + " │ ├─ op \"+\"\n"
/// + " │ └─ val \"w\"\n"
/// + " ├─ op \"+\"\n"
/// + " ├─ expr\n"
/// + " │ ├─ val \"x\"\n"
/// + " │ ├─ op \"+\"\n"
/// + " │ └─ val \"y\"\n"
/// + " ├─ op \"+\"\n"
/// + " └─ val \"z\"\n"
/// );
/// ```
///
/// [`String`]: https://doc.rust-lang.org/nightly/alloc/string/struct.String.html
/// [`ascii_tree::write_tree`]: ../ascii_tree/fn.write_tree.html
pub fn into_ascii_tree<R>(pairs: Pairs<R>) -> Result<String, std::fmt::Error>
where
R: pest::RuleType,
{
let nodes = into_ascii_tree_nodes(pairs);
let mut output = String::new();
match nodes.len() {
0 => {}
1 => {
ascii_tree::write_tree(&mut output, nodes.first().unwrap())?;
}
_ => {
let root = ascii_tree::Tree::Node(String::new(), nodes);
ascii_tree::write_tree(&mut output, &root)?;
if output.starts_with(" \n") {
output = output.split_off(2);
}
}
};
Ok(output)
}
/// Prints the result returned by your pest Parser as an ascii tree.
///
/// # Errors
/// In case of an parsing error, the error is printed.
/// In case of a formating error, the error is printed.
///
/// # Examples
/// ```ignore
/// pest_ascii_tree::print_ascii_tree(
/// ExpressionParser::parse(Rule::expr,
/// "(u + (v + w)) + (x + y) + z"));
/// ```
///
/// will result in the output
///
/// <pre>
/// expr
/// ├─ expr
/// │ ├─ val "u"
/// │ ├─ op "+"
/// │ └─ expr
/// │ ├─ val "v"
/// │ ├─ op "+"
/// │ └─ val "w"
/// ├─ op "+"
/// ├─ expr
/// │ ├─ val "x"
/// │ ├─ op "+"
/// │ └─ val "y"
/// ├─ op "+"
/// └─ val "z"
/// </pre>
///
pub fn print_ascii_tree<R>(parsing_result: Result<Pairs<R>, Error<R>>)
where
R: pest::RuleType,
{
match parsing_result {
Ok(pairs) => match into_ascii_tree(pairs) {
Ok(output) => {
println!("{}", output);
}
Err(e) => {
eprintln!("{}", e);
}
},
Err(e) => {
eprintln!("{}", e);
}
}
}
#[cfg(test)]
mod tests {
use super::into_ascii_tree;
use pest::Parser;
#[derive(Parser)]
#[grammar = "expression.pest"]
struct ExpressionParser;
#[test]
fn it_works() {
let result =
into_ascii_tree(ExpressionParser::parse(Rule::expr, "a + b + c").unwrap()).unwrap();
assert_eq!(
result,
String::new()
+ " expr\n"
+ " ├─ val \"a\"\n"
+ " ├─ op \"+\"\n"
+ " ├─ val \"b\"\n"
+ " ├─ op \"+\"\n"
+ " └─ val \"c\"\n"
);
let result =
into_ascii_tree(ExpressionParser::parse(Rule::expr_root, "x + y + z").unwrap())
.unwrap();
assert_eq!(
result,
String::new()
+ " ├─ val \"x\"\n"
+ " ├─ op \"+\"\n"
+ " ├─ val \"y\"\n"
+ " ├─ op \"+\"\n"
+ " └─ val \"z\"\n"
);
let result = into_ascii_tree(ExpressionParser::parse(Rule::val, "m").unwrap()).unwrap();
assert_eq!(result, String::new() + " val \"m\"\n");
let result = into_ascii_tree(
ExpressionParser::parse(Rule::expr, "(u + (v + w)) + (x + y) + z").unwrap(),
)
.unwrap();
assert_eq!(
result,
String::new()
+ " expr\n"
+ " ├─ expr\n"
+ " │ ├─ val \"u\"\n"
+ " │ ├─ op \"+\"\n"
+ " │ └─ expr\n"
+ " │ ├─ val \"v\"\n"
+ " │ ├─ op \"+\"\n"
+ " │ └─ val \"w\"\n"
+ " ├─ op \"+\"\n"
+ " ├─ expr\n"
+ " │ ├─ val \"x\"\n"
+ " │ ├─ op \"+\"\n"
+ " │ └─ val \"y\"\n"
+ " ├─ op \"+\"\n"
+ " └─ val \"z\"\n"
);
let result = into_ascii_tree(
ExpressionParser::parse(Rule::root, "(u + (v + w)) + (x + y) + z").unwrap(),
)
.unwrap();
assert_eq!(
result,
String::new()
+ " expr\n"
+ " ├─ expr\n"
+ " │ ├─ val \"u\"\n"
+ " │ ├─ op \"+\"\n"
+ " │ └─ expr\n"
+ " │ ├─ val \"v\"\n"
+ " │ ├─ op \"+\"\n"
+ " │ └─ val \"w\"\n"
+ " ├─ op \"+\"\n"
+ " ├─ expr\n"
+ " │ ├─ val \"x\"\n"
+ " │ ├─ op \"+\"\n"
+ " │ └─ val \"y\"\n"
+ " ├─ op \"+\"\n"
+ " └─ val \"z\"\n"
);
let result = into_ascii_tree(
ExpressionParser::parse(Rule::expr_root, "(u + (v + w)) + (x + y) + z").unwrap(),
)
.unwrap();
assert_eq!(
result,
String::new()
+ " ├─ expr\n"
+ " │ ├─ val \"u\"\n"
+ " │ ├─ op \"+\"\n"
+ " │ └─ expr\n"
+ " │ ├─ val \"v\"\n"
+ " │ ├─ op \"+\"\n"
+ " │ └─ val \"w\"\n"
+ " ├─ op \"+\"\n"
+ " ├─ expr\n"
+ " │ ├─ val \"x\"\n"
+ " │ ├─ op \"+\"\n"
+ " │ └─ val \"y\"\n"
+ " ├─ op \"+\"\n"
+ " └─ val \"z\"\n"
);
}
}