perf(linter): Eliminate unnecessary Iterator::collect() allocations by Copilot · Pull Request #12776 · oxc-project/oxc

Copilot · 2025-08-03T08:06:00Z

This PR addresses performance issues where Iterator::collect() was being used to create intermediate collections that were only iterated over, causing unnecessary memory allocations.

Changes Made

1. CFG Example (`crates/oxc_semantic/examples/cfg.rs`)

Before:

let nodes: Vec<_> = nodes.iter().map(|node| format!("{}", node.kind().debug_name())).collect();
if nodes.len() > 1 {
    format!("{}\\l", nodes.into_iter().map(|it| format!("\\l    {it}")).join(""))
} else {
    nodes.into_iter().join("")
}

After:

if nodes.len() > 1 {
    format!("{}\\l", nodes.iter().map(|node| format!("\\l    {}", node.kind().debug_name())).join(""))
} else {
    nodes.iter().map(|node| format!("{}", node.kind().debug_name())).join("")
}

The intermediate Vec was collected only to be immediately consumed by into_iter() for joining. Now we use the iterator directly.

2. React Exhaustive Dependencies Rule (`crates/oxc_linter/src/rules/react/exhaustive_deps.rs`)

Before:

let unnecessary_deps: Vec<_> = declared_dependencies.difference(&found_dependencies).collect();
// ... other code ...
for dep in unnecessary_deps {
    // iterate over the collected Vec
}

After:

for dep in declared_dependencies.difference(&found_dependencies) {
    // iterate directly over the difference iterator
}

The HashSet::difference() iterator was being collected into a Vec only to be iterated over in a for loop. Now we iterate directly over the difference iterator.

Impact

Memory: Eliminates unnecessary heap allocations for intermediate collections
Performance: Reduces allocation overhead and improves cache locality
Maintainability: Simplifies code by removing unnecessary intermediate variables

All existing tests continue to pass, ensuring these optimizations don't affect functionality.

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graphite-app · 2025-08-03T08:06:06Z

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… allocations Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

codspeed-hq · 2025-08-03T09:49:38Z

CodSpeed Instrumentation Performance Report

Merging #12776 will not alter performance

_{Comparing copilot/fix-b6a654c0-6087-492d-bcac-3d1ecff213db (8610c2c) with main (32dd0a3)}

Summary

✅ 34 untouched benchmarks

## [1.10.0] - 2025-08-06 ### 🚀 Features - 44ac5a1 linter: Add eslint/no-unassigned-vars rule (#11365) (yefan) - ce6eeee linter: Add `eslint/prefer-destructuring` rule (#12721) (yefan) - 9b35600 linter/jsx-a11y: Add support for mapped attributes in label association checks (#12805) (camc314) - 5475075 vscode/language_server: Add `tsConfigPath` option (#12484) (Sysix) - a754f7a linter: Support `countVoidThis` option in `max-params` rule (#12604) (yefan) ### 🐛 Bug Fixes - 2c1dab6 linter/no-unassigned-vars: False positive with variables in for loop (#12833) (camc314) - 5a24574 linter/func-style: Fix more false positives (#12828) (camc314) - 33a7320 linter/no-throw-literal: Fix unconditional recursion in `could_be_error` (#12819) (camc314) - a3aec6a linter/explicit-module-boundary-types: Debug assertion fail with top level return (#12820) (camc314) - 6efe457 linter/no-empty-function: Respect allow options for functions and arrow functions (#12814) (camc314) - 1c21c46 linter/new-cap: Fix panic with computed member expr (#12804) (camc314) - 45206dd linter: Apply fix span offset after fixing the section source text (#12758) (Sysix) - 1e97e35 linter/unicorn/prefer-structured-clone: Update Default implementation for `PreferStructuredCloneConfig` (#12791) (camc314) - d382159 linter/unicorn/prefer-object-from-entries: Update Default implementation for `PreferObjectFromEntriesConfig` (#12790) (camc314) - b07d29c linter/typescript/no-this-alias: Update Default implementation for `NoThisAliasConfig` (#12789) (camc314) - 0db34ab linter/react/jsx-filename-case: Update Default implementation for `JsxFilenameExtensionConfig` (#12788) (camc314) - ff84eff linter/jest/prefer-lowercase-title: Update Default implementation for `PreferLowercaseTitleConfig` (#12787) (camc314) - 5175c6d linter/jest/no-large-snapshots: Update Default implementation for `NoLargeSnapshotsConfig` (#12786) (camc314) - 0eaebcd linter/jest/no-deprecated-functions: Update Default implementation for `JestConfig` (#12785) (camc314) - 4265db7 linter/import/no-anonymous-default-export: Update Default implementation for `NoAnonymousDefaultExport` config (#12784) (camc314) - 6a360e3 linter/import/extensions: Update Default implementation for ExtensionsConfig (#12783) (camc314) - 42c8f29 linter: Default options for `eslint/no-else-return` (#12762) (Sysix) - 4eac511 linter: Default options for `eslint/no-unneeded-ternary` (#12761) (Sysix) - 9c01dbf linter: Default options for `eslint/new-cap` (#12760) (Sysix) - b25406f linter/explicit-function-return-types: Update default values in ExplicitFunctionReturnTypeConfig (#12718) (camc314) - ce5876d parser: Validate inner expression of type assertions in assignment targets (#12614) (camc314) - 5383331 linter/explicit-mod-boundary-types: False positive with jsx elements (#12678) (camc314) - d0e99b5 linter/explicit-mod-boundary-types: False positive with call expressions (#12677) (camc314) - 525137e linter: Add missing options to no-inner-declarations (#12661) (camc314) - fc4a327 linter: No-unused-vars false positive with class property initializers (#12660) (camc314) - 6af8631 linter/no-unused-vars: False positive with chain expression (#12609) (camc314) - 744ef52 linter: Correct `array-type` handling of `default: 'array-simple'` (#12607) (yefan) ### 🚜 Refactor - 3f37ed1 linter: Replace `lazy_static` with `std::sync::LazyLock` (#12822) (Copilot) - 69fd08d semantic: Improve unused label tracking and add debug assertions (#12812) (camc314) - 030e397 linter: Simplify parsing CLI args (#12802) (overlookmotel) - c0e224a linter: Store `ExternalRuleId` in `OxlintOverrides` not raw names (#12502) (camc314) - 61587e4 linter: Correct comment (#12792) (overlookmotel) - 5adcb98 linter: Use `u32` to keep track of last fixed source text position (#12696) (Sysix) - 77acc11 linter, transformer: Use `Scoping::symbol_is_unused` (#12666) (overlookmotel) - ecf1cff language_server: Simplify offset adjustment by using `Message.move_offset` (#12647) (Sysix) - 7695393 linter: Simplify offset adjustment by using `Message.move_offset` (#12595) (Sysix) - b36dc92 linter: Refactor large arrays to reduce binary size (#12603) (Boshen) - 3b9f1f0 linter: Update iter_outer_expressions to take AstNodes reference (#12583) (camc314) ### 📚 Documentation - e760fd4 linter: Complete linter rules documentation with missing "Why is this bad?" sections (#12757) (Copilot) - 514322c rust: Add minimal documentation to example files in crates directory (#12731) (Copilot) - 1d910d5 linter: Fix typescript/consistent-type-imports rule options to match TypeScript ESLint (#12707) (Copilot) - 45e2fe8 rust: Fix typos and grammar mistakes in Rust documentation comments (#12715) (Copilot) - 7660a88 linter: Improve linter rule documentation with "Why is this bad?" sections and enhanced examples (#12711) (Copilot) - de1de35 rust: Add comprehensive README.md documentation for all Rust crates (#12706) (Copilot) ### ⚡ Performance - 09ae2a9 linter: Eliminate unnecessary Iterator::collect() allocations (#12776) (Copilot) - 693673b linter: Reduce iterations when collecting directories for nested configs (#12329) (overlookmotel) ### 🎨 Styling - cacbd1e linter/no-empty-function: Order match arms consistently (#12815) (camc314) - c15da81 codegen, formatter, linter, minifier, transformer: Re-order imports (#12725) (Copilot) ### 🧪 Testing - 3957fcc linter/no-undef: Add test case for `TSImportType` (#12800) (camc314) - d8ccff7 oxlint: Add `Tester::test_fix` mehod (#12754) (Sysix) - c6bfb8a linter: Add rule configuration consistency test (#12744) (camc314) - 2ceb835 linter: Fix offset for partical source texts (#12594) (Sysix) Co-authored-by: camc314 <18101008+camc314@users.noreply.github.com>

## [1.10.0] - 2025-08-06 ### 🚀 Features - 44ac5a1 linter: Add eslint/no-unassigned-vars rule (oxc-project#11365) (yefan) - ce6eeee linter: Add `eslint/prefer-destructuring` rule (oxc-project#12721) (yefan) - 9b35600 linter/jsx-a11y: Add support for mapped attributes in label association checks (oxc-project#12805) (camc314) - 5475075 vscode/language_server: Add `tsConfigPath` option (oxc-project#12484) (Sysix) - a754f7a linter: Support `countVoidThis` option in `max-params` rule (oxc-project#12604) (yefan) ### 🐛 Bug Fixes - 2c1dab6 linter/no-unassigned-vars: False positive with variables in for loop (oxc-project#12833) (camc314) - 5a24574 linter/func-style: Fix more false positives (oxc-project#12828) (camc314) - 33a7320 linter/no-throw-literal: Fix unconditional recursion in `could_be_error` (oxc-project#12819) (camc314) - a3aec6a linter/explicit-module-boundary-types: Debug assertion fail with top level return (oxc-project#12820) (camc314) - 6efe457 linter/no-empty-function: Respect allow options for functions and arrow functions (oxc-project#12814) (camc314) - 1c21c46 linter/new-cap: Fix panic with computed member expr (oxc-project#12804) (camc314) - 45206dd linter: Apply fix span offset after fixing the section source text (oxc-project#12758) (Sysix) - 1e97e35 linter/unicorn/prefer-structured-clone: Update Default implementation for `PreferStructuredCloneConfig` (oxc-project#12791) (camc314) - d382159 linter/unicorn/prefer-object-from-entries: Update Default implementation for `PreferObjectFromEntriesConfig` (oxc-project#12790) (camc314) - b07d29c linter/typescript/no-this-alias: Update Default implementation for `NoThisAliasConfig` (oxc-project#12789) (camc314) - 0db34ab linter/react/jsx-filename-case: Update Default implementation for `JsxFilenameExtensionConfig` (oxc-project#12788) (camc314) - ff84eff linter/jest/prefer-lowercase-title: Update Default implementation for `PreferLowercaseTitleConfig` (oxc-project#12787) (camc314) - 5175c6d linter/jest/no-large-snapshots: Update Default implementation for `NoLargeSnapshotsConfig` (oxc-project#12786) (camc314) - 0eaebcd linter/jest/no-deprecated-functions: Update Default implementation for `JestConfig` (oxc-project#12785) (camc314) - 4265db7 linter/import/no-anonymous-default-export: Update Default implementation for `NoAnonymousDefaultExport` config (oxc-project#12784) (camc314) - 6a360e3 linter/import/extensions: Update Default implementation for ExtensionsConfig (oxc-project#12783) (camc314) - 42c8f29 linter: Default options for `eslint/no-else-return` (oxc-project#12762) (Sysix) - 4eac511 linter: Default options for `eslint/no-unneeded-ternary` (oxc-project#12761) (Sysix) - 9c01dbf linter: Default options for `eslint/new-cap` (oxc-project#12760) (Sysix) - b25406f linter/explicit-function-return-types: Update default values in ExplicitFunctionReturnTypeConfig (oxc-project#12718) (camc314) - ce5876d parser: Validate inner expression of type assertions in assignment targets (oxc-project#12614) (camc314) - 5383331 linter/explicit-mod-boundary-types: False positive with jsx elements (oxc-project#12678) (camc314) - d0e99b5 linter/explicit-mod-boundary-types: False positive with call expressions (oxc-project#12677) (camc314) - 525137e linter: Add missing options to no-inner-declarations (oxc-project#12661) (camc314) - fc4a327 linter: No-unused-vars false positive with class property initializers (oxc-project#12660) (camc314) - 6af8631 linter/no-unused-vars: False positive with chain expression (oxc-project#12609) (camc314) - 744ef52 linter: Correct `array-type` handling of `default: 'array-simple'` (oxc-project#12607) (yefan) ### 🚜 Refactor - 3f37ed1 linter: Replace `lazy_static` with `std::sync::LazyLock` (oxc-project#12822) (Copilot) - 69fd08d semantic: Improve unused label tracking and add debug assertions (oxc-project#12812) (camc314) - 030e397 linter: Simplify parsing CLI args (oxc-project#12802) (overlookmotel) - c0e224a linter: Store `ExternalRuleId` in `OxlintOverrides` not raw names (oxc-project#12502) (camc314) - 61587e4 linter: Correct comment (oxc-project#12792) (overlookmotel) - 5adcb98 linter: Use `u32` to keep track of last fixed source text position (oxc-project#12696) (Sysix) - 77acc11 linter, transformer: Use `Scoping::symbol_is_unused` (oxc-project#12666) (overlookmotel) - ecf1cff language_server: Simplify offset adjustment by using `Message.move_offset` (oxc-project#12647) (Sysix) - 7695393 linter: Simplify offset adjustment by using `Message.move_offset` (oxc-project#12595) (Sysix) - b36dc92 linter: Refactor large arrays to reduce binary size (oxc-project#12603) (Boshen) - 3b9f1f0 linter: Update iter_outer_expressions to take AstNodes reference (oxc-project#12583) (camc314) ### 📚 Documentation - e760fd4 linter: Complete linter rules documentation with missing "Why is this bad?" sections (oxc-project#12757) (Copilot) - 514322c rust: Add minimal documentation to example files in crates directory (oxc-project#12731) (Copilot) - 1d910d5 linter: Fix typescript/consistent-type-imports rule options to match TypeScript ESLint (oxc-project#12707) (Copilot) - 45e2fe8 rust: Fix typos and grammar mistakes in Rust documentation comments (oxc-project#12715) (Copilot) - 7660a88 linter: Improve linter rule documentation with "Why is this bad?" sections and enhanced examples (oxc-project#12711) (Copilot) - de1de35 rust: Add comprehensive README.md documentation for all Rust crates (oxc-project#12706) (Copilot) ### ⚡ Performance - 09ae2a9 linter: Eliminate unnecessary Iterator::collect() allocations (oxc-project#12776) (Copilot) - 693673b linter: Reduce iterations when collecting directories for nested configs (oxc-project#12329) (overlookmotel) ### 🎨 Styling - cacbd1e linter/no-empty-function: Order match arms consistently (oxc-project#12815) (camc314) - c15da81 codegen, formatter, linter, minifier, transformer: Re-order imports (oxc-project#12725) (Copilot) ### 🧪 Testing - 3957fcc linter/no-undef: Add test case for `TSImportType` (oxc-project#12800) (camc314) - d8ccff7 oxlint: Add `Tester::test_fix` mehod (oxc-project#12754) (Sysix) - c6bfb8a linter: Add rule configuration consistency test (oxc-project#12744) (camc314) - 2ceb835 linter: Fix offset for partical source texts (oxc-project#12594) (Sysix) Co-authored-by: camc314 <18101008+camc314@users.noreply.github.com>

Initial plan

9dfa706

Copilot AI assigned Copilot and Boshen Aug 3, 2025

Copilot started work on behalf of Boshen August 3, 2025 08:06 View session

Optimize unnecessary Iterator::collect usage by avoiding intermediate…

8610c2c

… allocations Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

Copilot AI requested a review from Boshen August 3, 2025 08:28

Copilot finished work on behalf of Boshen August 3, 2025 08:28

github-actions bot added A-linter Area - Linter A-semantic Area - Semantic labels Aug 3, 2025

Boshen changed the title ~~perf: Eliminate unnecessary Iterator::collect() allocations~~ perf(linter): Eliminate unnecessary Iterator::collect() allocations Aug 3, 2025

github-actions bot added the C-performance Category - Solution not expected to change functional behavior, only performance label Aug 3, 2025

Boshen marked this pull request as ready for review August 3, 2025 09:52

Boshen requested review from Dunqing and camc314 as code owners August 3, 2025 09:52

Boshen merged commit 09ae2a9 into main Aug 3, 2025
31 of 50 checks passed

Boshen deleted the copilot/fix-b6a654c0-6087-492d-bcac-3d1ecff213db branch August 3, 2025 10:01

This was referenced Aug 6, 2025

release(crates): v0.81.0 #12840

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release(oxlint): v1.10.0 #12846

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oxc-bot mentioned this pull request Aug 6, 2025

release(crates): v0.81.0 #12850

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perf(linter): Eliminate unnecessary Iterator::collect() allocations#12776

perf(linter): Eliminate unnecessary Iterator::collect() allocations#12776
Boshen merged 2 commits intomainfrom
copilot/fix-b6a654c0-6087-492d-bcac-3d1ecff213db

Copilot AI commented Aug 3, 2025 •

edited

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Copilot AI commented Aug 3, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Changes Made

1. CFG Example (crates/oxc_semantic/examples/cfg.rs)

2. React Exhaustive Dependencies Rule (crates/oxc_linter/src/rules/react/exhaustive_deps.rs)

Impact

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graphite-app bot commented Aug 3, 2025

How to use the Graphite Merge Queue

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codspeed-hq bot commented Aug 3, 2025

CodSpeed Instrumentation Performance Report

Merging #12776 will not alter performance

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Copilot AI commented Aug 3, 2025 •

edited

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1. CFG Example (`crates/oxc_semantic/examples/cfg.rs`)

2. React Exhaustive Dependencies Rule (`crates/oxc_linter/src/rules/react/exhaustive_deps.rs`)