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use rnix::{Root, SyntaxKind, SyntaxNode};
use rowan::ast::AstNode;
/// An assignment of an identifier to a value in the context of a REPL.
#[derive(Debug, Clone, PartialEq, Eq)]
pub(crate) struct Assignment<'a> {
pub(crate) ident: &'a str,
pub(crate) value: rnix::ast::Expr,
}
impl<'a> Assignment<'a> {
/// Try to parse an [`Assignment`] from the given input string.
///
/// Returns [`None`] if the parsing fails for any reason, since the intent is for us to
/// fall-back to trying to parse the input as a regular expression or other REPL commands for
/// any reason, since the intent is for us to fall-back to trying to parse the input as a
/// regular expression or other REPL command.
pub fn parse(input: &'a str) -> Option<Self> {
let mut tt = rnix::tokenizer::Tokenizer::new(input);
macro_rules! next {
($kind:ident) => {{
loop {
let (kind, tok) = tt.next()?;
if kind == SyntaxKind::TOKEN_WHITESPACE {
continue;
}
if kind != SyntaxKind::$kind {
return None;
}
break tok;
}
}};
}
let ident = next!(TOKEN_IDENT);
let _equal = next!(TOKEN_ASSIGN);
let (green, errs) = rnix::parser::parse(tt);
let value = Root::cast(SyntaxNode::new_root(green))?.expr()?;
if !errs.is_empty() {
return None;
}
Some(Self { ident, value })
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn simple_assignments() {
for input in ["x = 4", "x = \t\t\n\t4", "x=4"] {
let res = Assignment::parse(input).unwrap();
assert_eq!(res.ident, "x");
assert_eq!(res.value.to_string(), "4");
}
}
#[test]
fn complex_exprs() {
let input = "x = { y = 4; z = let q = 7; in [ q (y // { z = 9; }) ]; }";
let res = Assignment::parse(input).unwrap();
assert_eq!(res.ident, "x");
}
#[test]
fn not_an_assignment() {
let input = "{ x = 4; }";
let res = Assignment::parse(input);
assert!(res.is_none(), "{input:?}");
}
}
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