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perf(parser): avoid re-allocating when parsing import stmt #20666

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Merged
graphite-app merged 1 commit into from
Mar 24, 2026
+64 −15
Merged

perf(parser): avoid re-allocating when parsing import stmt #20666

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47 changes: 47 additions & 0 deletions crates/oxc_parser/src/cursor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -481,6 +481,53 @@ impl<'a, C: Config> ParserImpl<'a, C> {
}
}

pub(crate) fn parse_delimited_list_into<F, T>(
&mut self,
list: &mut Vec<'a, T>,
close: Kind,
separator: Kind,
opening_span: Span,
mut f: F,
) -> Option<u32>
where
F: FnMut(&mut Self) -> T,
{
// Cache cur_kind() to avoid redundant calls in compound checks
let kind = self.cur_kind();
if kind == close
|| matches!(kind, Kind::Eof | Kind::Undetermined)
|| self.fatal_error.is_some()
{
return None;
}
list.push(f(self));
loop {
let kind = self.cur_kind();
if kind == close
|| matches!(kind, Kind::Eof | Kind::Undetermined)
|| self.fatal_error.is_some()
{
return None;
}
if !self.at(separator) {
self.set_fatal_error(diagnostics::expect_closing_or_separator(
close.to_str(),
separator.to_str(),
kind.to_str(),
self.cur_token().span(),
opening_span,
));
return None;
}
self.advance(separator);
if self.cur_kind() == close {
let trailing_separator = self.prev_token_end - 1;
return Some(trailing_separator);
}
list.push(f(self));
}
}

pub(crate) fn parse_delimited_list_with_rest<E, A, R, D>(
&mut self,
close: Kind,
Expand Down
24 changes: 13 additions & 11 deletions crates/oxc_parser/src/js/module.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -287,8 +287,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
default_span,
));
}
let mut import_specifiers = self.parse_import_specifiers(import_kind);
specifiers.append(&mut import_specifiers);
self.parse_import_specifiers_into(&mut specifiers, import_kind);
}
_ => return self.unexpected(),
}
Expand All @@ -309,8 +308,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
specifiers.push(self.parse_import_namespace_specifier());
} else if self.at(Kind::LCurly) {
// import { export1 , export2 as alias2 , [...] } from "module-name";
let mut import_specifiers = self.parse_import_specifiers(import_kind);
specifiers.append(&mut import_specifiers);
self.parse_import_specifiers_into(&mut specifiers, import_kind);
}

self.expect(Kind::From);
Expand All @@ -328,19 +326,23 @@ impl<'a, C: Config> ParserImpl<'a, C> {
}

// import { export1 , export2 as alias2 , [...] } from "module-name";
fn parse_import_specifiers(
fn parse_import_specifiers_into(
&mut self,
specifiers: &mut Vec<'a, ImportDeclarationSpecifier<'a>>,
import_kind: ImportOrExportKind,
) -> Vec<'a, ImportDeclarationSpecifier<'a>> {
) {
let opening_span = self.cur_token().span();
self.expect(Kind::LCurly);
let (list, _) = self.context_remove(self.ctx, |p| {
p.parse_delimited_list(Kind::RCurly, Kind::Comma, opening_span, |parser| {
parser.parse_import_specifier(import_kind)
})
self.context_remove(self.ctx, |p| {
let _ = p.parse_delimited_list_into(
specifiers,
Kind::RCurly,
Kind::Comma,
opening_span,
|parser| parser.parse_import_specifier(import_kind),
);
});
self.expect(Kind::RCurly);
list
}

/// [Import Attributes](https://tc39.es/proposal-import-attributes)
Expand Down
8 changes: 4 additions & 4 deletions tasks/track_memory_allocations/allocs_parser.snap
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Original file line number Diff line number Diff line change
@@ -1,14 +1,14 @@
File | File size || Sys allocs | Sys reallocs || Arena allocs | Arena reallocs | Arena bytes
-------------------------------------------------------------------------------------------------------------------------------------------
checker.ts | 2.92 MB || 9672 | 21 || 267678 | 22847
checker.ts | 2.92 MB || 9672 | 21 || 267677 | 22847

cal.com.tsx | 1.06 MB || 1083 | 49 || 138159 | 13699
cal.com.tsx | 1.06 MB || 1083 | 49 || 136164 | 13698

RadixUIAdoptionSection.jsx | 2.52 kB || 1 | 0 || 365 | 66
RadixUIAdoptionSection.jsx | 2.52 kB || 1 | 0 || 363 | 66

pdf.mjs | 567.30 kB || 703 | 75 || 90678 | 8148

antd.js | 6.69 MB || 7132 | 235 || 528505 | 55357

binder.ts | 193.08 kB || 530 | 7 || 16791 | 1467
binder.ts | 193.08 kB || 530 | 7 || 16790 | 1467

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