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//! Sub-module of [`common`][crate::common] for parsing identifiers.
use core::str;
use crate::{span::Spanned, SourceCodeScanner};
impl<'src> SourceCodeScanner<'src> {
/// Consumes an identifier defined by the two input predicates and returns it.
///
/// The first predicate defines acceptable values for the first character in the identifier,
/// the second defines acceptable values for the rest of the identifier's characters.
///
/// If the first predicate originally matched, then this function will return a [`prim@str`] reference of all
/// consumed characters along with the [`Span`][crate::span::Span] of the consumed region. If not, [None] is
/// returned and no characters are consumed.
///
/// # Examples
/// ```rust
/// # use alkale::SourceCodeScanner;
/// # use alkale::span::Span;
/// fn first_char(c: char) -> bool {
/// c == '#'
/// }
///
/// fn rest_char(c: char) -> bool {
/// c.is_ascii_alphabetic()
/// }
///
/// let scanner = SourceCodeScanner::new("#abc h #whatever");
///
/// # unsafe {
/// assert_eq!(
/// scanner.try_consume_identifier(first_char, rest_char),
/// Some(Span::new(0, 4).wrap("#abc"))
/// );
///
/// scanner.skip();
///
/// assert_eq!(
/// scanner.try_consume_identifier(first_char, rest_char),
/// None
/// );
///
/// assert_eq!(scanner.next(), Some('h'));
/// scanner.skip();
///
/// assert_eq!(
/// scanner.try_consume_identifier(first_char, rest_char),
/// Some(Span::new(7, 9).wrap("#whatever"))
/// );
///
/// assert_eq!(
/// scanner.try_consume_identifier(first_char, rest_char),
/// None
/// );
/// # }
/// ```
///
/// # See Also
/// If you are looking to match typical language identifiers (that is, `[a-zA-Z_][a-zA-Z0-9_]*`),
/// use [`try_consume_standard_identifier`][Self::try_consume_standard_identifier].
#[inline]
pub fn try_consume_identifier<F: Fn(char) -> bool, G: Fn(char) -> bool>(
&self,
first_predicate: F,
rest_predicate: G,
) -> Option<Spanned<&'src str>> {
// Peek the next character, exit if it doesn't exist.
let first_char = self.peek()?;
// If the peeked character doesn't match the predicate, exit.
if !first_predicate(first_char) {
return None;
}
let ident = self.capture_str(|| {
self.skip();
while let Some(char) = self.peek() {
if rest_predicate(char) {
self.skip();
} else {
break;
}
}
});
Some(ident)
}
/// Consumes an identifier defined by the regex `[a-zA-Z_][a-zA-Z0-9_]*`.
///
/// This method will return a [`prim@str`] reference of all consumed characters along
/// with the [`Span`][crate::span::Span] of the consumed region. If the pattern didn't match,
/// [None] is returned and no characters are consumed.
///
/// # Examples
/// ```rust
/// # use alkale::SourceCodeScanner;
/// # use alkale::span::Span;
/// let scanner = SourceCodeScanner::new("ident 3 whatever");
///
/// # unsafe {
/// assert_eq!(
/// scanner.try_consume_standard_identifier(),
/// Some(Span::new(0, 5).wrap("ident"))
/// );
///
/// scanner.skip();
///
/// assert_eq!(
/// scanner.try_consume_standard_identifier(),
/// None
/// );
///
/// assert_eq!(scanner.next(), Some('3'));
/// scanner.skip();
///
/// assert_eq!(
/// scanner.try_consume_standard_identifier(),
/// Some(Span::new(8, 8).wrap("whatever"))
/// );
///
/// assert_eq!(
/// scanner.try_consume_standard_identifier(),
/// None
/// );
///
/// # }
/// ```
///
/// # See Also
/// If you are looking to match identifiers more generally, use [`try_parse_identifier`][Self::try_consume_identifier].
#[inline]
pub fn try_consume_standard_identifier(&self) -> Option<Spanned<&'src str>> {
self.try_consume_identifier(
|x| x.is_ascii_alphabetic() || x == '_',
|x| x.is_ascii_alphanumeric() || x == '_',
)
}
}
#[cfg(test)]
mod tests {
use crate::{
span::{Span, Spannable},
SourceCodeScanner,
};
macro_rules! edge_case {
($name:ident, $($code:literal => $result:expr),* $(,)?) => {
#[test]
fn $name() {
$({
let code = SourceCodeScanner::new($code);
assert_eq!(
code.try_consume_standard_identifier(),
$result,
);
})*
}
}
}
#[test]
fn try_parse_standard_identifier() {
let code = SourceCodeScanner::new("awesome b23 0 ident$ifier");
// SAFETY: Spans are valid.
unsafe {
assert_eq!(
code.try_consume_standard_identifier(),
Some("awesome".spanned(Span::new(0, 7)))
);
code.skip();
assert_eq!(
code.try_consume_standard_identifier(),
Some("b23".spanned(Span::new(8, 3)))
);
code.skip();
assert_eq!(code.try_consume_standard_identifier(), None);
assert_eq!(code.next(), Some('0'));
code.skip();
assert_eq!(
code.try_consume_standard_identifier(),
Some("ident".spanned(Span::new(14, 5)))
);
assert_eq!(code.next(), Some('$'));
assert_eq!(
code.try_consume_standard_identifier(),
Some("ifier".spanned(Span::new(20, 5)))
);
assert_eq!(code.try_consume_standard_identifier(), None);
assert!(!code.has_next());
}
}
#[test]
fn try_parse_identifier() {
let code = SourceCodeScanner::new("awesome b23 0 ident$ifier");
let initial = |x: char| x.is_alphanumeric();
let internal = |x: char| x.is_alphanumeric() || x == '$';
// SAFETY: Spans are all valid.
unsafe {
assert_eq!(
code.try_consume_identifier(initial, internal),
Some("awesome".spanned(Span::new(0, 7)))
);
code.skip();
assert_eq!(
code.try_consume_identifier(initial, internal),
Some("b23".spanned(Span::new(8, 3)))
);
code.skip();
assert_eq!(
code.try_consume_identifier(initial, internal),
Some("0".spanned(Span::new(12, 1)))
);
code.skip();
assert_eq!(
code.try_consume_identifier(initial, internal),
Some("ident$ifier".spanned(Span::new(14, 11)))
);
assert_eq!(code.try_consume_identifier(initial, internal), None);
assert!(!code.has_next());
}
}
edge_case!(empty, "" => None);
edge_case!(space, " " => None);
// SAFETY: Span is valid.
edge_case!(single_char, "x" => unsafe { Some(Span::new(0, 1).wrap("x")) });
// SAFETY: Spans are valid.
edge_case!(garbage_after,
"ident@#%)_@)%" => unsafe { Some(Span::new(0, 5).wrap("ident")) },
"x@" => unsafe { Some(Span::new(0, 1).wrap("x")) },
);
edge_case!(untrimmed, " ident " => None);
}