perf(parser): remove string search from parsing JSX element name

[overlookmotel]

Optimization to parsing JSX.

When parsing JSX element names parse_jsx_element_name has to determine if the identifier:

1. starts with a lowercase letter, and
2. contains a -.

The 2nd check is relatively expensive - string search.

Avoid the search by making the lexer feed this information (which it already has) to the parser. This reduces the check in the parser to just !contains_dash.

(came across this while working on #23712)

[overlookmotel]

• perf(parser): remove string search from parsing JSX element name #23713 👈 (View in Graphite)
• main

---

How to use the Graphite Merge Queue

Add either label to this PR to merge it via the merge queue:

• 0-merge - adds this PR to the back of the merge queue
• hotfix - for urgent changes, fast-track this PR to the front of the merge queue

You must have a Graphite account in order to use the merge queue. Sign up using this link.

An organization admin has enabled the Graphite Merge Queue in this repository.

Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue.

This stack of pull requests is managed by Graphite. Learn more about stacking.

[Copilot]

Pull request overview

Optimizes JSX parsing in oxc_parser by avoiding per-identifier string searches for '-' when classifying JSX element names, instead reusing information already available during lexing.

Changes:

• Changed parse_jsx_identifier to return (JSXIdentifier, contains_dash) so callers can avoid name.contains('-').
• Updated JSX element-name classification and member-expression parsing to use contains_dash.
• Updated continue_lex_jsx_identifier to return a bool indicating whether retokenization occurred.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
crates/oxc_parser/src/jsx/mod.rs	Propagates a lexer-derived contains_dash flag through JSX identifier parsing to eliminate name.contains('-') searches.
crates/oxc_parser/src/cursor.rs	Makes continue_lex_jsx_identifier return a boolean so the parser can cheaply detect hyphenated JSX identifiers.

[codspeed-hq]

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 9 skipped benchmarks¹

---

_{Comparing om/06-21-perf_parser_remove_string_search_from_parsing_jsx_element_name (0338837) with main (cf5e47e)}

Footnotes

1. 9 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[overlookmotel]

Not sure who to ask to review, so I've asked you both @Dunqing and @camc314. Whoever gets to it first...

[camc314]

🚀

[camc314]

Merge activity

• Jun 22, 4:47 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Jun 22, 4:47 PM UTC: camc314 added this pull request to the Graphite merge queue.
• Jun 22, 4:54 PM UTC: Merged by the Graphite merge queue.