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