perf(linter/eslint/no-underscore-dangle): avoid String clone per identifier#24371
Merged
Merged
Conversation
…tifier `is_allowed` did `self.allow.contains(&name.to_string())`, heap-allocating a String per checked identifier for a membership test. Compare by reference with `iter().any` instead.
Merging this PR will not alter performance
Comparing 
Footnotes
|
Boshen
added a commit
that referenced
this pull request
Jul 14, 2026
# Oxlint ### 🚀 Features - 0433a83 linter/eslint/no-inner-declarations: Add `namespaces` option (#24044) (Boshen) - 92f154a oxlint,oxfmt: Auto-discover `.mts` config files (#24357) (camc314) - 8c1d74b linter/import/no-duplicates: Add autofix logic (#24273) (Cole Ellison) ### 🐛 Bug Fixes - 0b086de linter/jest/prefer-lowercase-title: False positive when `lowercaseFirstCharacterOnly` is false (#24414) (Connor Shea) - 097cb95 linter: Allow `vite-plus/test` and `@effect as Vitest source (#24196) (Liang) - 8337835 linter: Error on `ignorePatterns` that cannot match files aoutside the config directory (#24341) (leaysgur) - 9ba30e5 linter/oxc/bad-replace-all-arg: Add note to enhance diagnostic (#24346) (camc314) - 2ce5a33 linter: Resolve `ignorePatterns` relative to the config dir (#24339) (leaysgur) - ab90eed linter/eslint/no-loop-func: Do not error on catch variables (#24316) (Chris Opperwall) - b67f0a6 linter/eslint/no-unused-vars: Count default parameter updates as usage (#24323) (camc314) - d193f8e linter: Detect Junie agent env vars (#24277) (Jeevan Mohan Pawar) - 2aecf60 linter/eslint/no-unreachable: Handle `break` in switch stmts correctly (#24260) (camc314) ### ⚡ Performance - 7f80cac linter/vue/prop-name-casing: Precompile `ignoreProps` regex pattern (#24413) (connorshea) - 6272051 linter/typescript/no-require-imports: Compile allow patterns once (#24417) (connorshea) - fb1edf1 linter: Compute comment fix span only for directive comments (#24419) (connorshea) - 33805b9 linter/jsdoc/require-param: Compile checkTypesPattern regex once (#24420) (connorshea) - 8de6fca linter/jest/valid-title: Compile disallowedWords regex once (#24412) (Connor Shea) - 4a0d8dc linter/eslint/no-underscore-dangle: Avoid String clone per identifier (#24371) (Ian Macalinao) - f3ab04c linter/typescript/consistent-type-imports: Remove redundant Vec per violation (#24370) (Ian Macalinao) - 4d2d78d linter/typescript/prefer-ts-expect-error: Avoid String clone per comment (#24369) (Ian Macalinao) # Oxfmt ### 🚀 Features - 3a7fe74 formatter_css: Update oxc-css-parser to 0.0.7 (#24434) (leaysgur) - 0173cd3 formatter_css: Format Less :extend and merge props (#24358) (leaysgur) - 92f154a oxlint,oxfmt: Auto-discover `.mts` config files (#24357) (camc314) - df250df formatter: Support `quoteProps` for TS enum and methods (#24309) (leaysgur) - a9a5cd6 formatter_core: Expose `SourceText::as_str()` (#24281) (leaysgur) ### 🐛 Bug Fixes - 162bddf formatter: Add required parens for conditional type in type parameter constraint (#24450) (leaysgur) - 2d22a91 formatter: Determine type cast target from span instead of lexical scan (#24447) (leaysgur) - 25306e9 formatter: Do not add extra parens with type cast comment (#24444) (leaysgur) - bd6edfe formatter: Break arrow signature that exactly fills the line when cond body may hug (#24440) (leaysgur) - a99ef41 formatter: Keep quotes on method signature named new (#24432) (leaysgur) - fcc28df formatter_css: Keep glued-braket-value tight (#24352) (leaysgur) - 8337835 linter: Error on `ignorePatterns` that cannot match files aoutside the config directory (#24341) (leaysgur) - b7c7e15 formatter: Add parens for import and private field in new callee chain (#24320) (leaysgur) - 0c8f6e4 formatter: Update detect_code_removal for #24309 (#24314) (leaysgur) - a85aad0 formatter: Fix member-chain and non-null parens (#24312) (leaysgur) - 1c29c73 formatter: Preserve `TSNonNullExpression` in chain expression (#24311) (leaysgur) - 8933c0e formatter: Keep comment inside of empty `switch` block (#24308) (leaysgur) - ec26af2 formatter: Preserve blank lines between JSX attrs (#24290) (leaysgur) - 70bd54d formatter: Keep arrow function body comment (#24287) (leaysgur) - 415fe1e oxfmt: Error on ignorePatterns that cannot match files outside the config directory (#24286) (leaysgur) - eeabc4a formatter_css: Bail on EOF-recovered parse errors (#24282) (leaysgur) - 42ec8de formatter: Keep comments inside surviving parens and suppressed statement terminators (#24253) (leaysgur) - 1343779 formatter: Keep comment inline for empty statements (#24249) (leaysgur) - b996579 formatter: Print ; before trailing comments part 2 (#24246) (leaysgur) - 4f86e8c formatter: Print `;` before trailing comments (#24244) (leaysgur) - 01252e4 formatter: Add or remove parens for `let` declaration (#24215) (leaysgur) ### ⚡ Performance - eeb1913 formatter_core: Avoid per-call `Vec` work-stack in soft-line removal (#23775) (Marius Schulz) - a2f255b formatter: Use `SmallVec` for `MemberChain` collections (#23776) (Marius Schulz) ### 📚 Documentation - b52d0f5 formatter: Add TODO comment about unsound code (#24372) (overlookmotel) Co-authored-by: Boshen <[email protected]>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
What
NoUnderscoreDangle::is_allowedheap-allocated aString(name.to_string()) on every call, onlyto feed
Vec::containsfor a membership test:is_allowedruns fromreport, which fires for every checked identifier (bindings, members,private fields, function/method/property names).
self.allowis aVec<String>andnameisalready
&str, so theto_string()allocates a throwawayStringpurely to compare it, then dropsit — once per identifier the rule inspects.
Change
Compare against the existing
Strings by reference; no allocation:Impact
One heap allocation removed per checked identifier. Measured on a synthetic 8k-line TS file with
8,000 dangling-underscore identifiers (
eslint/no-underscore-dangleas the only enabled rule),counting system-allocator activity during
Linter::runonly:The −8,000 allocs/iter exactly equals the number of identifiers checked (one
to_stringeach).Wall clock
This is a memory/allocation optimization, not a speed one — same class as #23751 (whose own
wall-clock delta was only −0.7% to −4%). In an isolated single-rule Criterion benchmark
(release build,
tasks/benchmark, the repo's deterministicNeverGrowInPlaceallocator),the change trends flat (fixed faster in only 20/40 paired runs — no measurable wall-clock change; the removed
Stringis dwarfed by the rule's unavoidable per-diagnostic message allocations), but the effect is small and near the noise floor of a sharedmachine, so no end-to-end speedup should be assumed. The reliable, deterministic win is the
reduced allocation count above (production uses mimalloc, where these small allocations are
cheap).
Verification
cargo test -p oxc_linter --lib no_underscore_danglepasses.This PR was assisted by Claude Code.