perf(linter/jsx-a11y): skip lowercasing non-aria attribute names by linyiru · Pull Request #23906 · oxc-project/oxc

linyiru · 2026-06-28T16:26:17Z

What

aria-props and aria-proptypes run on every JSXAttribute. Both lowercased the
attribute name up-front via cow_to_ascii_lowercase() purely to test the aria-
prefix:

let name = get_jsx_attribute_name(&attr.name);
let name = name.cow_to_ascii_lowercase(); // allocates for camelCase names
if name.starts_with("aria-") && ... { ... }

cow_to_ascii_lowercase() allocates a fresh String whenever the name contains an
uppercase byte — i.e. for the very common camelCase attributes (className,
onClick, onChange, tabIndex, …) that are then discarded because they are not
aria-*.

This gates on the prefix first with the allocation-free
oxc_linter::utils::starts_with_ignore_case (the helper introduced in #23861), and
only lowercases for the rare attribute that actually is aria-* — which still needs
the lowercased form for the property lookup and the diagnostic message.

Correctness

Behavior-preserving:

The new starts_with_ignore_case(name, "aria-") gate matches exactly the same
names the old cow_to_ascii_lowercase().starts_with("aria-") did (both are
ASCII-case-insensitive over the 5-byte prefix).
For matched aria-* attributes the name is still lowercased before the
is_valid_aria_property / AriaProperty::try_from lookup and before being passed
to the diagnostic, so emitted diagnostics are byte-identical.
Non-aria-* attributes never produced a diagnostic and still don't.

The full pass/fail/fix suites and snapshots for both rules are unchanged.

Measurement

Predicate microbench over a realistic 39-name JSX attribute distribution (mostly
non-aria-*, several camelCase), release + LTO:

prefix check	per scan (39 attrs)
`cow_to_ascii_lowercase().starts_with("aria-")`	329.9 ns
`starts_with_ignore_case(name, "aria-")`	40.6 ns

~8x on the prefix check, from removing the per-attribute allocation. The
corpus-level impact is for CI CodSpeed to quantify; this is the same allocation-free
pattern as the merged #23861.

Disclosure: developed with AI assistance (Claude), reviewed and verified by the author.

`aria-props` and `aria-proptypes` run on every `JSXAttribute` and lowercased the attribute name via `cow_to_ascii_lowercase()` only to test the `aria-` prefix. That allocates a fresh `String` for any name containing an uppercase byte — i.e. the common camelCase attributes (`className`, `onClick`, …) that are discarded because they are not `aria-*`. Gate on the prefix first with the allocation-free `starts_with_ignore_case`, and lowercase only for the rare attribute that is actually `aria-*` (still needed for the property lookup and the diagnostic message). Diagnostics are unchanged.

codspeed-hq · 2026-06-28T16:35:02Z

Merging this PR will not alter performance

✅ 5 untouched benchmarks
⏩ 66 skipped benchmarks¹

_{Comparing linyiru:perf/jsx-a11y-skip-lowercase (b90c4ee) with main (eedf4c7)}

66 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. ↩

camc314

thanks!

# Oxlint ### 💥 BREAKING CHANGES - 88f4455 str: [**BREAKING**] `Str` and `Ident` methods take `&GetAllocator` (#23781) (overlookmotel) ### 🚀 Features - f2091b3 ast: Unify old and new `AstBuilder`s (#23875) (overlookmotel) - 1c8f50c linter: Add schema for `eslint/no-restricted-import` (#23642) (Sysix) ### 🐛 Bug Fixes - 7cb85c4 linter/eslint/no-negated-condition: Add autofix for negated conditions (#23825) (Yagiz Nizipli) - f7d1f50 oxlint, oxfmt: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate (#23886) (overlookmotel) - d891990 linter/jsx-a11y/role-supports-aria-props: Ignore nullish prop values (#23865) (Mikhail Baev) - 94b6599 linter: Deduplicate missing plugin errors (#23853) (camc314) - eff3eff linter/oxc/branches-sharing-code: Avoid else-if false positives (#23843) (camc314) - 2a2d3b9 linter/eslint/prefer-destructuring: Skip `AssignmentExpression` autofixes (#23818) (camc314) - ddc24ae linter/eslint/id-length: Respect checkGeneric for mapped type keys (#23802) (bab) - cd89202 linter/react/exhaustive-deps: Skip wrapper expression when analyzing hook initializers (#23793) (camc314) - 20e8285 linter/unicorn/prefer-native-coercion-function: Allow ts type predicates (#23774) (camc314) - d86f60b lsp: Normalize user config path to watch pattern (#23723) (Sysix) - 52032cf linter: Newline-terminate tsgolint errors (#23762) (Mikhail Baev) - 368fda7 linter/eslint/no-warning-comments: Avoid dropping generated regex patterns (#23741) (camc314) - ce44fbd linter/valid-title: Escape disallowed words regex (#23742) (camc314) - 3100d11 linter/prefer-called-exactly-once-with: Avoid out-of-bounds slice panic at end of file (#23625) (Jerry Zhao) - 742be36 refactor/node/handle-callback-err: Reject invalid regex config (#23740) (camc314) - d7be179 linter/eslint/no-restricted-globals: Handle shadowed locals (#23736) (camc314) - b3b1ff8 linter/vitest/expect-expect: Handle global vitest detection correctly (#23734) (camc314) ### ⚡ Performance - 68f9472 linter/jsx-a11y: Skip lowercasing non-aria attribute names (#23906) (Lawrence Lin) - b9312b4 linter/unicorn/prefer-export-from: Use keyed binding lookup (#23893) (Marius Schulz) - cd5204e linter/typescript/no-unsafe-declaration-merging: Use keyed binding lookup (#23894) (Marius Schulz) - e948498 linter/eslint/prefer-named-capture-group: Only dispatch for relevant node types (#23868) (Connor Shea) - 4ac7a8e linter/eslint/max-depth: Derive node types (#23896) (Connor Shea) - daeed09 linter/eslint/no-restricted-globals: Only scan unresolved references (#23890) (camc314) - e808514 linter/jest-vitest: Speed up no-standalone-expect (#23883) (camc314) - 8b165e5 linter/react/exhaustive-deps: Skip non-reactive calls early (#23882) (camc314) - 54005e7 linter/eslint/no-unused-vars: Precompute exported bindings (#23881) (camc314) - 9bc2f8c linter/unicorn/prefer-number-properties: Speed up global checks (#23880) (camc314) - 4ff104f linter: Optimize `require-hook` and `prefer-mock-*` rules to run on specific node types (#23871) (Connor Shea) - cc2213b linter: Run `no-underscore-dangle` only when relevant node types are present (#23867) (Connor Shea) - 3e55c21 linter/promise/always-return: Narrow to function node types (#23878) (Connor Shea) - 7136182 linter/jest-vitest: Speed up no-commented-out-tests (#23864) (camc314) - f138264 linter/eslint/no-script-url: Match javascript: prefix without allocating (#23861) (Lawrence Lin) - 7ef6895 linter/react/no-array-index-key: Delay index symbol lookup (#23857) (camc314) - 26bc171 linter/react/no-array-index-key: Match callback methods directly (#23856) (camc314) - 44fbbda linter/jsx-a11y/interactive-supports-focus: Check cheap conditions first (#23854) (camc314) - 84a5aa3 linter/eslint/no-extend-native: Skip lowercase references early (#23851) (camc314) - 88a74b2 linter/eslint/no-nonoctal-decimal-escape: Scan decimal escapes as bytes (#23850) (camc314) - fca69a8 linter: Skip traversal without this expressions (#23845) (camc314) - 838fd63 linter: Reduce preallocation for per-file diagnostics `Vec` (#23705) (Marius Schulz) - 417b506 linter/typescript/array-type: Remove full source text clone (#23751) (Marius Schulz) ### 📚 Documentation - 57e4469 linter/unicorn: Update prefer-dom-node-text-content rationale (#23933) (Mikhail Baev) - 3d61dea all: Correct capitalization in comments (#23887) (overlookmotel) ### 🛡️ Security - 3cdd18f deps: Update npm packages (#23690) (renovate[bot]) # Oxfmt ### 💥 BREAKING CHANGES - 259e0cd oxfmt,formatter_graphql: [**BREAKING**] Support draft syntax with removing prettier fallback (#23326) (leaysgur) - accbc49 oxfmt: [**BREAKING**] Format `parser:css,less,scss` files + css-in-js by `oxc_formatter_css` (#23321) (leaysgur) ### 🚀 Features - dffa4b3 formatter_css: Implement `oxc_formatter_css` (#23320) (leaysgur) - 01de9ec oxfmt: Format `parser:graphql` files by `oxc_formatter_graphql` (#23318) (leaysgur) - 4e66212 formatter_graphql: Implement oxc_formatter_graphql (#23317) (leaysgur) ### 🐛 Bug Fixes - 67325ae formatter_css: Handle frontmatter language (#23819) (leaysgur) - 3f355e5 formatter_graphql: Improve major prettier diffs (#23419) (leaysgur) - 48e2d78 formatter_css: Improve major prettier diffs (#23327) (leaysgur) - 8c07cad all: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate in tests (#23888) (overlookmotel) - f7d1f50 oxlint, oxfmt: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate (#23886) (overlookmotel) - d86f60b lsp: Normalize user config path to watch pattern (#23723) (Sysix) ### ⚡ Performance - 4ddcba0 formatter_core: Add printable-ASCII fast path to TextWidth (#23913) (Lawrence Lin) ### 📚 Documentation - b4d0dc9 oxfmt,formatter,formatter_css,formatter_core: Update AGENTS.md (#23814) (leaysgur) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com> Co-authored-by: Cameron <cameron.clark@hey.com>

) ## What `aria-props` and `aria-proptypes` run on every `JSXAttribute`. Both lowercased the attribute name up-front via `cow_to_ascii_lowercase()` purely to test the `aria-` prefix: ```rust let name = get_jsx_attribute_name(&attr.name); let name = name.cow_to_ascii_lowercase(); // allocates for camelCase names if name.starts_with("aria-") && ... { ... } ``` `cow_to_ascii_lowercase()` allocates a fresh `String` whenever the name contains an uppercase byte — i.e. for the very common camelCase attributes (`className`, `onClick`, `onChange`, `tabIndex`, …) that are then discarded because they are not `aria-*`. This gates on the prefix first with the allocation-free `oxc_linter::utils::starts_with_ignore_case` (the helper introduced in #23861), and only lowercases for the rare attribute that actually is `aria-*` — which still needs the lowercased form for the property lookup and the diagnostic message. ## Correctness Behavior-preserving: - The new `starts_with_ignore_case(name, "aria-")` gate matches exactly the same names the old `cow_to_ascii_lowercase().starts_with("aria-")` did (both are ASCII-case-insensitive over the 5-byte prefix). - For matched `aria-*` attributes the name is still lowercased before the `is_valid_aria_property` / `AriaProperty::try_from` lookup and before being passed to the diagnostic, so emitted diagnostics are byte-identical. - Non-`aria-*` attributes never produced a diagnostic and still don't. The full pass/fail/fix suites and snapshots for both rules are unchanged. ## Measurement Predicate microbench over a realistic 39-name JSX attribute distribution (mostly non-`aria-*`, several camelCase), release + LTO: | prefix check | per scan (39 attrs) | | --- | --- | | `cow_to_ascii_lowercase().starts_with("aria-")` | 329.9 ns | | `starts_with_ignore_case(name, "aria-")` | 40.6 ns | ~8x on the prefix check, from removing the per-attribute allocation. The corpus-level impact is for CI CodSpeed to quantify; this is the same allocation-free pattern as the merged #23861. --- _Disclosure: developed with AI assistance (Claude), reviewed and verified by the author._ Co-authored-by: Cameron <cameron.clark@hey.com>

# Oxlint ### 💥 BREAKING CHANGES - 88f4455 str: [**BREAKING**] `Str` and `Ident` methods take `&GetAllocator` (#23781) (overlookmotel) ### 🚀 Features - f2091b3 ast: Unify old and new `AstBuilder`s (#23875) (overlookmotel) - 1c8f50c linter: Add schema for `eslint/no-restricted-import` (#23642) (Sysix) ### 🐛 Bug Fixes - 7cb85c4 linter/eslint/no-negated-condition: Add autofix for negated conditions (#23825) (Yagiz Nizipli) - f7d1f50 oxlint, oxfmt: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate (#23886) (overlookmotel) - d891990 linter/jsx-a11y/role-supports-aria-props: Ignore nullish prop values (#23865) (Mikhail Baev) - 94b6599 linter: Deduplicate missing plugin errors (#23853) (camc314) - eff3eff linter/oxc/branches-sharing-code: Avoid else-if false positives (#23843) (camc314) - 2a2d3b9 linter/eslint/prefer-destructuring: Skip `AssignmentExpression` autofixes (#23818) (camc314) - ddc24ae linter/eslint/id-length: Respect checkGeneric for mapped type keys (#23802) (bab) - cd89202 linter/react/exhaustive-deps: Skip wrapper expression when analyzing hook initializers (#23793) (camc314) - 20e8285 linter/unicorn/prefer-native-coercion-function: Allow ts type predicates (#23774) (camc314) - d86f60b lsp: Normalize user config path to watch pattern (#23723) (Sysix) - 52032cf linter: Newline-terminate tsgolint errors (#23762) (Mikhail Baev) - 368fda7 linter/eslint/no-warning-comments: Avoid dropping generated regex patterns (#23741) (camc314) - ce44fbd linter/valid-title: Escape disallowed words regex (#23742) (camc314) - 3100d11 linter/prefer-called-exactly-once-with: Avoid out-of-bounds slice panic at end of file (#23625) (Jerry Zhao) - 742be36 refactor/node/handle-callback-err: Reject invalid regex config (#23740) (camc314) - d7be179 linter/eslint/no-restricted-globals: Handle shadowed locals (#23736) (camc314) - b3b1ff8 linter/vitest/expect-expect: Handle global vitest detection correctly (#23734) (camc314) ### ⚡ Performance - 68f9472 linter/jsx-a11y: Skip lowercasing non-aria attribute names (#23906) (Lawrence Lin) - b9312b4 linter/unicorn/prefer-export-from: Use keyed binding lookup (#23893) (Marius Schulz) - cd5204e linter/typescript/no-unsafe-declaration-merging: Use keyed binding lookup (#23894) (Marius Schulz) - e948498 linter/eslint/prefer-named-capture-group: Only dispatch for relevant node types (#23868) (Connor Shea) - 4ac7a8e linter/eslint/max-depth: Derive node types (#23896) (Connor Shea) - daeed09 linter/eslint/no-restricted-globals: Only scan unresolved references (#23890) (camc314) - e808514 linter/jest-vitest: Speed up no-standalone-expect (#23883) (camc314) - 8b165e5 linter/react/exhaustive-deps: Skip non-reactive calls early (#23882) (camc314) - 54005e7 linter/eslint/no-unused-vars: Precompute exported bindings (#23881) (camc314) - 9bc2f8c linter/unicorn/prefer-number-properties: Speed up global checks (#23880) (camc314) - 4ff104f linter: Optimize `require-hook` and `prefer-mock-*` rules to run on specific node types (#23871) (Connor Shea) - cc2213b linter: Run `no-underscore-dangle` only when relevant node types are present (#23867) (Connor Shea) - 3e55c21 linter/promise/always-return: Narrow to function node types (#23878) (Connor Shea) - 7136182 linter/jest-vitest: Speed up no-commented-out-tests (#23864) (camc314) - f138264 linter/eslint/no-script-url: Match javascript: prefix without allocating (#23861) (Lawrence Lin) - 7ef6895 linter/react/no-array-index-key: Delay index symbol lookup (#23857) (camc314) - 26bc171 linter/react/no-array-index-key: Match callback methods directly (#23856) (camc314) - 44fbbda linter/jsx-a11y/interactive-supports-focus: Check cheap conditions first (#23854) (camc314) - 84a5aa3 linter/eslint/no-extend-native: Skip lowercase references early (#23851) (camc314) - 88a74b2 linter/eslint/no-nonoctal-decimal-escape: Scan decimal escapes as bytes (#23850) (camc314) - fca69a8 linter: Skip traversal without this expressions (#23845) (camc314) - 838fd63 linter: Reduce preallocation for per-file diagnostics `Vec` (#23705) (Marius Schulz) - 417b506 linter/typescript/array-type: Remove full source text clone (#23751) (Marius Schulz) ### 📚 Documentation - 57e4469 linter/unicorn: Update prefer-dom-node-text-content rationale (#23933) (Mikhail Baev) - 3d61dea all: Correct capitalization in comments (#23887) (overlookmotel) ### 🛡️ Security - 3cdd18f deps: Update npm packages (#23690) (renovate[bot]) # Oxfmt ### 💥 BREAKING CHANGES - 259e0cd oxfmt,formatter_graphql: [**BREAKING**] Support draft syntax with removing prettier fallback (#23326) (leaysgur) - accbc49 oxfmt: [**BREAKING**] Format `parser:css,less,scss` files + css-in-js by `oxc_formatter_css` (#23321) (leaysgur) ### 🚀 Features - dffa4b3 formatter_css: Implement `oxc_formatter_css` (#23320) (leaysgur) - 01de9ec oxfmt: Format `parser:graphql` files by `oxc_formatter_graphql` (#23318) (leaysgur) - 4e66212 formatter_graphql: Implement oxc_formatter_graphql (#23317) (leaysgur) ### 🐛 Bug Fixes - 67325ae formatter_css: Handle frontmatter language (#23819) (leaysgur) - 3f355e5 formatter_graphql: Improve major prettier diffs (#23419) (leaysgur) - 48e2d78 formatter_css: Improve major prettier diffs (#23327) (leaysgur) - 8c07cad all: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate in tests (#23888) (overlookmotel) - f7d1f50 oxlint, oxfmt: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate (#23886) (overlookmotel) - d86f60b lsp: Normalize user config path to watch pattern (#23723) (Sysix) ### ⚡ Performance - 4ddcba0 formatter_core: Add printable-ASCII fast path to TextWidth (#23913) (Lawrence Lin) ### 📚 Documentation - b4d0dc9 oxfmt,formatter,formatter_css,formatter_core: Update AGENTS.md (#23814) (leaysgur) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com> Co-authored-by: Cameron <cameron.clark@hey.com>

linyiru requested a review from camc314 as a code owner June 28, 2026 16:26

camc314 reviewed Jun 28, 2026

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Comment thread crates/oxc_linter/src/rules/jsx_a11y/aria_props.rs

camc314 approved these changes Jun 28, 2026

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Merge branch 'main' into perf/jsx-a11y-skip-lowercase

b90c4ee

camc314 added the A-linter Area - Linter label Jun 28, 2026

camc314 self-assigned this Jun 28, 2026

camc314 merged commit 68f9472 into oxc-project:main Jun 28, 2026
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oxc-guard Bot mentioned this pull request Jun 29, 2026

release(apps): oxlint v1.72.0 && oxfmt v0.57.0 #23935

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perf(linter/jsx-a11y): skip lowercasing non-aria attribute names#23906

perf(linter/jsx-a11y): skip lowercasing non-aria attribute names#23906
camc314 merged 2 commits into
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linyiru:perf/jsx-a11y-skip-lowercase

linyiru commented Jun 28, 2026

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linyiru commented Jun 28, 2026

What

Correctness

Measurement

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Merging this PR will not alter performance

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codspeed-hq Bot commented Jun 28, 2026 •

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