perf(linter/no-useless-escape): drop unnecessary Vec collect#22171
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Pull request overview
This PR optimizes the no-useless-escape lint rule’s string scanning by removing an intermediate Vec allocation during backslash detection, keeping behavior the same while reducing per-literal overhead.
Changes:
- Removed collection of
memmem::find_iter(..., "\\")results into aVecand iterated the iterator directly. - Dropped an
is_empty()early return that was redundant given the existing empty-Vecfallthrough.
Merging this PR will not alter performance
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camc314
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May 6, 2026
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Another memory allocation optimization, also simplifies the code a bit. Below is Claude's summary. --- ## Summary `check_string` collected `memmem::find_iter(bytes, "\\")` into a `Vec<usize>` just to iterate it once. The `is_empty()` early-return wasn't buying anything either since `vec\![]` doesn't allocate — the existing `offsets = vec\![]` fallthrough already produces the same empty result. Iterate `find_iter` directly. Eliminates one Vec allocation per string literal that contains a backslash. ## Benchmark Paired interleaved benchmark (N=60, alternating order, parse-only control). Fixture: 30 files × 2000 string literals, 20% containing backslashes. ### Wall-clock | | Baseline | Optimized | Δ | |---|---|---|---| | Rule on | 11.74 ms | 11.08 ms | **−0.65 ms** | | Parse-only | 7.93 ms | 7.86 ms | −0.07 ms (noise) | | Rule-attributable | | | **−0.58 ms** | - Paired t-statistic: **4.04** (well above |t|>2 threshold) - Win/Loss/Tie: **41/19/0** - Parse-only control t=0.53 confirms the signal isn't from binary layout effects. ### Allocations (counting global allocator, rule-attributable = total − parse-only) | Metric | Baseline | Optimized | Saved | Reduction | |---|---|---|---|---| | Alloc count | 78,501 | 66,664 | **11,837** | **15%** | | Alloc bytes | 5.78 MB | 3.70 MB | **2.08 MB** | **36%** | ## Test plan - [x] \`cargo test -p oxc_linter no_useless_escape\` — passes - [x] \`cargo clippy -p oxc_linter --no-deps -- -D warnings\` — clean - [x] \`just fmt\` — no changes needed - [x] Behavioral parity confirmed (\`--format=json\` diff shows only \`start_time\`) 🤖 Generated with [Claude Code](https://claude.com/claude-code)
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# Oxlint ### 💥 BREAKING CHANGES - 00ce512 oxlint/lsp: [**BREAKING**] Don't fix suggestions on fixAll code actions & command (#22195) (Sysix) ### 🚀 Features - 0eeceaf linter/no-unused-vars: Rename parameter with initializer (#22308) (camc314) - fa0232b linter/no-unused-vars: Add param rename suggestion (#22285) (Ryota Misumi) - ae59305 linter/promise/no-promise-in-callback: Add `exemptDeclarations` option (#22275) (Mikhail Baev) - 60bed4a linter: Extends `no-redundant-roles` and `prefer-tag-over-role` support roles (#22069) (mehm8128) - 545c80f linter/eslint: Implement `prefer-regex-literals` rule (#22192) (Mikhail Baev) - cf86d7a linter: Bulk suppression (#19328) (Said Atrahouch) - 23abd22 linter/jsx-a11y: Implement no-noninteractive-element-to-interactive-role (#21264) (Pedro Tainha) - fbb8f22 linter: Support `ignores` in overrides (#22148) (camc314) - 5a4414d oxlint/lsp: Support `rulesCustomization` lsp option (#21858) (Sysix) ### 🐛 Bug Fixes - 610f4c7 linter/no-unused-vars: Avoid renaming captured vars (#22310) (camc314) - 6b50f23 oxlint/cli: Load root config by searching up parent directories (#22272) (Sysix) - 31a5de7 linter: Rename override `ignores` to `excludeFiles` (#22283) (camc314) - 26d5d7b linter: Add missing vitest/valid-describe-callback functionality (#22279) (camchenry) - 784530f linter: `valid-title`: detect `String.raw` strings (#22271) (Sysix) - 080d90e linter: Move `no-debugger` fix to suggestion (#22256) (Sysix) - 25b7017 linter: Undocument override `ignores` option (#22213) (camc314) - 7bb00dd linter: Fix role-has-required-aria-props (#22097) (mehm8128) - d25279e linter/disable-directives: Improve parsing of names, descriptions (#22184) (camc314) - a59e447 linter/disable-directives: Ignore invalid enable suffixes (#22179) (camc314) - aafef0f ci: Disable bulk supression test on big endian (#22175) (camc314) - 281daec linter/vue/define-props-destructuring: Add `only-when-assigned` config opt (#22142) (camc314) - 46ab679 linter/plugins: Trim leading newline for partial sources (#20928) (bab) - 29ff6d9 linter: Update docs for no_alias_methods rule to be Vitest-specific and add toThrowError alias (#22129) (camchenry) ### ⚡ Performance - 9414bee linter/role-has-required-aria-props: Avoid intermediate vec (#22212) (camc314) - 3883ea3 linter/no-useless-escape: Drop unnecessary Vec collect (#22171) (connorshea) - 42c3029 linter/check-property-names: Replace split-collect-pop-join with rfind (#22172) (connorshea) - 9551d53 linter: Remove unnecessary Vec collect in CFG edge traversal (#22167) (connorshea) - 26fa2fc linter/aria-role: Remove unnecessary string allocations in run method (#22168) (connorshea) - c9ce045 linter/getter-return: Remove unnecessary Vec collect in CFG edge traversal (#22166) (connorshea) - 72bd846 linter/no-this-in-sfc: Reorder cheap name check, avoid String allocation (#22164) (connorshea) ### 📚 Documentation - 4da212a linter/no-unused-vars: Add docs to `rename_unused_function_parameter` (#22311) (camc314) - 27c4628 linter/forbid-dom-props: Escape jsx examples in lint rule docs (#22254) (4MBL) - 3f81147 linter: Improve the `react/jsx-key` rule docs. (#22162) (connorshea) - 07f03cc linter/consistent-return: Add note about `noImplicitReturns` coverage (#22156) (camc314) - 7c1e049 oxlint/lsp: Improve autogenerated lsp docs (#22154) (Sysix) - 87b3e38 linter: Update docs to be vitest-specific for consistent-test-it (#22128) (camchenry) # Oxfmt ### 💥 BREAKING CHANGES - 5c6c390 oxfmt: [**BREAKING**] Respect more git ignore options, align with Oxlint (#22210) (leaysgur) ### 🚀 Features - 6e8e818 oxfmt: Experimental .svelte support (#21700) (leaysgur) ### 🐛 Bug Fixes - e2a20b6 formatter: Add space after commas in import attributes (#22274) (Leonabcd123) ### ⚡ Performance - b756682 oxfmt: Optimize nested config prescan (#22232) (Jovi De Croock) - f14e81e formatter/sort_imports: Skip sort for single import runs (#22204) (leaysgur) - 32255b1 formatter: Process `ImportDeclaration`s in a run (#22079) (overlookmotel) ### 📚 Documentation - 4da6f4c formatter: Correct comment (#22217) (overlookmotel) - ef3507d formatter/sort_imports: Refresh docs (#22203) (leaysgur) Co-authored-by: Cameron <cameron.clark@hey.com>
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Another memory allocation optimization, also simplifies the code a bit.
Below is Claude's summary.
Summary
check_stringcollectedmemmem::find_iter(bytes, "\\")into aVec<usize>just to iterate it once. Theis_empty()early-return wasn't buying anything either sincevec\![]doesn't allocate — the existingoffsets = vec\![]fallthrough already produces the same empty result.Iterate
find_iterdirectly. Eliminates one Vec allocation per string literal that contains a backslash.Benchmark
Paired interleaved benchmark (N=60, alternating order, parse-only control). Fixture: 30 files × 2000 string literals, 20% containing backslashes.
Wall-clock
Allocations (counting global allocator, rule-attributable = total − parse-only)
Test plan
🤖 Generated with Claude Code