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perf(parser): cleanup and optimize parsing jsx #14234

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Sep 30, 2025
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perf(parser): cleanup and optimize parsing jsx #14234

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43 changes: 13 additions & 30 deletions crates/oxc_parser/src/jsx/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,17 +4,15 @@ use oxc_allocator::{Box, Dummy, Vec};
use oxc_ast::ast::*;
use oxc_span::{Atom, GetSpan, Span};

use crate::{Context, ParserImpl, diagnostics, lexer::Kind};
use crate::{ParserImpl, diagnostics, lexer::Kind};

impl<'a> ParserImpl<'a> {
pub(crate) fn parse_jsx_expression(&mut self) -> Expression<'a> {
let span = self.start_span();
self.bump_any(); // bump `<`
let kind = self.cur_kind();
if kind == Kind::RAngle {
self.expect_jsx_child(Kind::RAngle);
let opening_fragment = self.ast.jsx_opening_fragment(self.end_span(span));
Expression::JSXFragment(self.parse_jsx_fragment(span, opening_fragment, false))
Expression::JSXFragment(self.parse_jsx_fragment(span, false))
} else if kind.is_identifier_or_keyword() {
Expression::JSXElement(self.parse_jsx_element(span, false))
} else {
Expand All @@ -24,12 +22,9 @@ impl<'a> ParserImpl<'a> {

/// `JSXFragment` :
/// < > `JSXChildren_opt` < / >
fn parse_jsx_fragment(
&mut self,
span: u32,
opening_fragment: JSXOpeningFragment,
in_jsx_child: bool,
) -> Box<'a, JSXFragment<'a>> {
fn parse_jsx_fragment(&mut self, span: u32, in_jsx_child: bool) -> Box<'a, JSXFragment<'a>> {
self.expect_jsx_child(Kind::RAngle);
let opening_fragment = self.ast.jsx_opening_fragment(self.end_span(span));
let children = self.parse_jsx_children();
let closing_fragment = self.parse_jsx_closing_fragment(in_jsx_child);
self.ast.alloc_jsx_fragment(
Expand Down Expand Up @@ -61,10 +56,10 @@ impl<'a> ParserImpl<'a> {
/// true when inside jsx element, false when at top level expression
fn parse_jsx_element(&mut self, span: u32, in_jsx_child: bool) -> Box<'a, JSXElement<'a>> {
let (opening_element, self_closing) = self.parse_jsx_opening_element(span, in_jsx_child);
let children = if self_closing { self.ast.vec() } else { self.parse_jsx_children() };
let closing_element = if self_closing {
None
let (children, closing_element) = if self_closing {
(self.ast.vec(), None)
} else {
let children = self.parse_jsx_children();
let closing_element = self.parse_jsx_closing_element(in_jsx_child);
if !Self::jsx_element_name_eq(&opening_element.name, &closing_element.name) {
self.error(diagnostics::jsx_element_no_match(
Expand All @@ -73,7 +68,7 @@ impl<'a> ParserImpl<'a> {
opening_element.name.span().source_text(self.source_text),
));
}
Some(closing_element)
(children, Some(closing_element))
};
self.ast.alloc_jsx_element(self.end_span(span), opening_element, children, closing_element)
}
Expand Down Expand Up @@ -248,13 +243,7 @@ impl<'a> ParserImpl<'a> {
self.bump_any(); // bump `<`
// <> open fragment
if self.at(Kind::RAngle) {
self.expect_jsx_child(Kind::RAngle);
let opening_fragment = self.ast.jsx_opening_fragment(self.end_span(span));
return Some(JSXChild::Fragment(self.parse_jsx_fragment(
span,
opening_fragment,
true,
)));
return Some(JSXChild::Fragment(self.parse_jsx_fragment(span, true)));
}
// <ident open element
if self.at(Kind::Ident) || self.cur_kind().is_any_keyword() {
Expand Down Expand Up @@ -304,7 +293,7 @@ impl<'a> ParserImpl<'a> {
let expr = self.ast.jsx_empty_expression(Span::new(span.start + 1, span.end - 1));
JSXExpression::EmptyExpression(expr)
} else {
let expr = JSXExpression::from(self.parse_jsx_assignment_expression());
let expr = JSXExpression::from(self.parse_expr());
if in_jsx_child {
self.expect_jsx_child(Kind::RCurly);
} else {
Expand All @@ -316,16 +305,10 @@ impl<'a> ParserImpl<'a> {
self.ast.alloc_jsx_expression_container(self.end_span(span_start), expr)
}

fn parse_jsx_assignment_expression(&mut self) -> Expression<'a> {
self.context(Context::default().and_await(self.ctx.has_await()), self.ctx, |p| {
p.parse_expr()
})
}

/// `JSXChildExpression` :
/// { ... `AssignmentExpression` }
fn parse_jsx_spread_child(&mut self, span_start: u32) -> Box<'a, JSXSpreadChild<'a>> {
let expr = self.parse_jsx_assignment_expression();
let expr = self.parse_expr();
self.expect_jsx_child(Kind::RCurly);
self.ast.alloc_jsx_spread_child(self.end_span(span_start), expr)
}
Expand Down Expand Up @@ -369,7 +352,7 @@ impl<'a> ParserImpl<'a> {
let span = self.start_span();
self.bump_any(); // bump `{`
self.expect(Kind::Dot3);
let argument = self.parse_jsx_assignment_expression();
let argument = self.parse_expr();
self.expect(Kind::RCurly);
self.ast.alloc_jsx_spread_attribute(self.end_span(span), argument)
}
Expand Down
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