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perf(formatter): optimize RegExpLiteral formatting to avoid heap allocations #17797

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Merged
graphite-app merged 1 commit into from
Jan 9, 2026
Merged

perf(formatter): optimize RegExpLiteral formatting to avoid heap allocations #17797

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19 changes: 13 additions & 6 deletions crates/oxc_formatter/src/write/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1118,12 +1118,19 @@ impl<'a> FormatWrite<'a> for AstNode<'a, BigIntLiteral<'a>> {
impl<'a> FormatWrite<'a> for AstNode<'a, RegExpLiteral<'a>> {
fn write(&self, f: &mut Formatter<'_, 'a>) {
let raw = self.raw().unwrap().as_str();
let (pattern, flags) = raw.rsplit_once('/').unwrap();
// TODO: print the flags without allocation.
let mut flags = flags.chars().collect::<std::vec::Vec<_>>();
flags.sort_unstable();
let flags = flags.iter().collect::<String>();
let s = StringBuilder::from_strs_array_in([pattern, "/", &flags], f.context().allocator());

let Some((pattern, flags)) = raw.rsplit_once('/') else {
return write!(f, text(raw));
};

// Regex flags are ASCII and limited to at most 8 unique: d, g, i, m, s, u, v, y
debug_assert!(flags.len() <= 8 && flags.is_ascii());
let mut flags_buf = [0u8; 8];
let len = flags.len();
flags_buf[..len].copy_from_slice(flags.as_bytes());
flags_buf[..len].sort_unstable();
let flags = str::from_utf8(&flags_buf[..len]).unwrap();
let s = StringBuilder::from_strs_array_in([pattern, "/", flags], f.context().allocator());
write!(f, text(s.into_str()));
}
}
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